guide-o-learn - Speciss College
A Guide to the Speciss Auto Electrics Certificate
Reproduced by Speciss College with permission from Kevin Sullivan -
Contains chapters on:
 Health & Safety
 Equipment & Tools
 Electrical Fundamentals
 Digital Multimeters
 General Electrical System Diagnosis
 Circuit Protection
 Wire Repair – Battery
 Fundamentals of Electro Magnetism
 Starter Systems
 Charging Systems
 Lighting Systems
 Wiring Diagrams
 Gauges & Warning Devices
 Wiper/Washer Circuits
 Signal Horn - Auxiliary Lights
 Alarm Systems
 Tow-Bar Electrics
 Wiring Symbols
 Auto Electrical Glossary of Terms
Reproduced by Speciss College with permission from Kevin Sullivan -
Name of Chapter
Chapter 1: Health & Safety in the Workshop
Chapter 2: Equipment & Tools
Chapter 3: Classification of Combustion Engines
Chapter 4: Basic Function of Combustion Engines:
SI and CI Engine
Chapter 5: Drive Line Assemblies
Chapter 6: Auto Electrical Assemblies
Chapter 7: Electrical Fundamentals
Chapter 8: Digital Multimeters
Chapter 9: General Electrical System Diagnosis
Chapter 10: Circuit Protection
Chapter 11: Wire Repair
Chapter 12: The Battery
Chapter 13: Fundamentals of Electromagnetism
Chapter 14: Starting System
Chapter 15: Charging System
Chapter 16: Conventional Ignition System
Chapter 17: Lighting System
Chapter 18: Wiring Diagrams
Chapter 19: Gauges, Warning Devices & Driver Info
Chapter 20: Connector Repair
Chapter 21: Accessories: Wiper, Washer and Horn
Chapter 22: Enhance Vehicle Electrical Systems
Chapter 23: Outlook on Topics in Diploma Course
Appendix A: Wiring Diagram Symbols
Appendix B: Auto Electric Glossary of Terms
Reproduced by Speciss College with permission from Kevin Sullivan -
Chapter 1: Health & Safety in the Workshop
Basic safety introduction
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Don't underestimate the dangers
Just because it so commonplace, it is sometimes easy to overlook the
many potential risks involved in vehicle servicing and repair. Thousands
of injuries are reported to local health and safety authorities, but many
more go unreported.
Accidents and injuries can happen at anytime
Here are just a few examples:
 Fires and explosions are a constant hazard wherever there are
flammable fuels
 Electricity can kill you very quickly, as well as cause painful shocks
and burns
 Heavy equipment and machinery can easily cause broken bones or
crush fingers and toes
 Hazardous solvents and other chemicals can burn or blind as well as
contribute to many kinds of illness
 Trips and falls can be caused by things such oil spills, and by tools
left lying around
 Poor lifting and handling techniques can cause chronic strain
injuries, particularly to your back
Accidents and injuries are avoidable
Your workplace will be a much safer place if YOU:
 Learn and follow all of the correct safety procedures - every time
 Always wear the right protective clothing
 Stay alert and aware of what is happening around you
 Think about how what you are doing could affect others
 Know what to do in an emergency
 Document and report all accidents and injuries whenever they
happen, and do everything you can to make sure they never happen
Safety is the responsibility of everyone in the workplace including you.
Make sure that you understand and follow all the
regulations and safety procedures that apply in your own
Personal protection
Figure 1-1: ISO First
Protective clothing (used in the automotive industry) is Aid Symbol
Reproduced by Speciss College with permission from Kevin Sullivan -
clothing designed to protect either the wearer's body or other items of
clothing from hazards such as heat, chemicals and toxic dust.
Basic injury prevention
There are many issues that may affect your safety. You should keep long
hair and loose clothing away from machinery, and additional protective
equipment may be needed depending on the job at hand. Also remember
to lift heady objects correctly to prevent back injuries.
Basic first aid
When assisting an injured person, be aware of any dangers that may still
be present and always seek professional advice when tending to an
injured person.
Property security
Check your customer's vehicle before you start to work on it. If there are
any valuables in it, or any damage to the paintwork, note them on your
job sheet and refer them to the customer or to your supervisor.
Hazardous waste materials
These are chemicals, or components, that the workshop no longer needs
that pose a danger to the environment and people if they are disposed of
in ordinary garbage cans or sewers. However, no material is considered
hazardous waste until the shop has finished using it and is ready to
dispose of it.
Used oil is any petroleum-based or synthetic oil that has been used.
During normal use, impurities such as dirt, metal scrapings, water, or
chemicals can get mixed in with the oil. Eventually, this used oil must be
replaced with virgin or re-refined oil.
NOTE: The release of only 1 litre of used oil can make 1 million litres
of fresh water undrinkable.
If used oil is dumped down the drain and enters a sewage treatment
plant, concentrations as small as 50 to 100 parts per million (ppm) in the
wastewater can foul sewage treatment processes.
Never mix a listed hazardous waste, gasoline, wastewater, halogenated
solvent, antifreeze, or an unknown waste material with used oil. Adding
any of these substances will cause the used oil to become contaminated,
which classifies it as hazardous waste.
Storage and disposal of used oil
Once oil has been used, it can be collected, recycled, and used over and
over again.
Reproduced by Speciss College with permission from Kevin Sullivan -
Recycled used oil can sometimes be used again for the same job or can
take on a completely different task. For example, used engine oil can be
re-refined and sold at some discount stores as engine oil or processed for
furnace fuel oil. After collecting used oil in an appropriate container the
material must be disposed of in one of two ways.
 Transporting offsite for recycling
 Burned in an onsite or offsite approved heater for energy recovery
Storage and disposal of brake fluid
Most brake fluid is made from polyglycol, is water soluble, and can be
considered hazardous if it has absorbed metals from the brake system.
Collect brake fluid in a container clearly marked to indicate that it is
designated for that purpose.
Do not mix brake fluid with used engine oil.
Do not pour brake fluid down drains or onto the ground.
Recycle brake fluid through a registered recycler.
Chapter 2: Equipment & Tools
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Figure 2-1: Basic Automotive Tools
Reproduced by Speciss College with permission from Kevin Sullivan -
The Most Common Automotive Repair Tools
Not every tool on this list is of the handheld variety, but everything is
useful in some way or another when working on your car. This list is
meant to be a resource for aspiring mechanics. Pros will likely have their
own list of most common car repair tools, but then, they already know
what they need.
 Spanners: Combination end spanners, both standard and metric, are
vital for engine work. With a box end on one side and an open end on
the other, they are useful for a wide range of applications. A hex or
Allen spanner set is also needed. While it is not the most common, a
torque wrench is needed for fine tuned calibration.
 Socket Set: Sockets in common metric sizes, both shallow and deep
sets, and a variety of drivers and extensions are also commonly used
for even the most basic repairs.
 Locking Pliers: Locking pliers are adjustable, locking pliers that apply
tremendous force and hold whatever you need them to in place so you
can free your hands for other tasks.
 Pliers: Needle nose pliers and regular pliers are useful for both the
tasks they are intended for and other things you can‘t think of until you
need the tool.
 Wire Cutters: For automotive electrical work, wire cutters are needed.
Sometimes wire cutters double as needle nose pliers.
 Voltmeter or Multimeter: To test for voltage or amperage, a
multimeter is very useful so you don‘t end up cutting wire you should
not and for testing components for power.
 Ball Peen Hammer: This type of hammer, smaller with a bulb in place
of a claw on one side of its head, is a good tool to have around for
freeing up stuck parts and other uses.
 Pry Bar: A pry bar gives you leverage to get up and under something
that will not budge. Where human strength ends, a pry bar takes over.
 Screwdrivers: Many components of a car are fastened with screws or
hose clamps that require a common Phillips head, flathead or square
head driver to loosen or tighten it.
 Feeler Gauge: When measuring spark plug gap or valve clearance, a
feeler gauge is necessary. Strips of steel of different precisely machined
thicknesses, a feeler gauge can tell the difference in terms of fractions
of a millimetre.
 Micrometer: While a feeler gauge measures gaps, a micrometer
measure distances, only extremely accurately. It is a precision tool and
not extremely common, but it is very useful.
Reproduced by Speciss College with permission from Kevin Sullivan -
Car Ramps: To get the front end of a car up off the ground without
using a lift, a car ramp can turn a difficult job into a much easier one.
These are the most common auto tools you will use for the most basic
repairs. There are numerous others, most of which have very specific
applications, but having the tools on this list at your disposal will enable
you to do a lot of work on your whole car.
Because of the complexity of cars and trucks today, many specialized
automotive tools must be used to build, maintain, and repair them. From
common tools such as screwdrivers and sockets, to more specialized
tools like spark plug pullers and diagnostic gauges, automotive tools are
essential in order to properly work on cars and trucks today. Many
automotive tools can be purchased at any hardware store, while others
must be obtained from specialized distributors; some of the more
specialized tools can be cost-prohibitive, while others are quite affordable.
A good set of automotive tools starts with a socket set and a set of
screwdrivers. Countless bolts and nuts hold a car or truck together, and
sockets and screwdrivers can tighten or loosen most of them. A
comprehensive set of sockets will include both metric and standard sizes,
as the sizes of the nuts and bolts vary from manufacturer to
manufacturer. Some bolts in an engine compartment can be quite difficult
to reach, so a variety of socket extenders are a good addition to the
socket set. Extra long screwdrivers can also make repairs easier.
Because much of the car's components are fixed underneath the vehicle,
lifts must be used so the mechanic can access the bottom of the vehicle.
More advanced hydraulic lifts use large beams and hydraulic pressure to
raise the car off the ground. Other simpler lifts, such as bottle jacks or
scissor jacks, can use hydraulic pressure or a screw system to raise the
Figure 2-2: Some auto electrical tools
Reproduced by Speciss College with permission from Kevin Sullivan -
Chapter 3: Classification of Combustion Engines
Identifying engines
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Multi-cylinder engines are produced in four common configurations. They
are: Inline, "Vee", Horizontally Opposed, and Rotary engines. Multicylinder engines are produced in three common configurations. They are:
 Inline
 "Vee"
 Horizontally Opposed
Inline engines can be found in 2, 3, 4, 5, and 6 cylinder configurations.
Cylinders arranged side by side in a single row identify the 'Inline' engine.
They can be mounted longitudinally (lengthwise) or transversely
(sideways) in the engine bay. However, it is uncommon to find a longer 6cylinder engine mounted transversely.
Figure 3-1: Classification according to cylinder layout
Reproduced by Speciss College with permission from Kevin Sullivan -
"Vee" engines are shorter than an equivalent capacity inline engine. They
can be found in 2, 4, 6, 8, 10 and 12 cylinder configurations and consist of
two banks of cylinders arranged in a Vee that is joined at the bottom.
They are shorter than inline engines, because offsetting the wider top
parts of alternate cylinders into the different arms of the Vee allows them
to be connected closer together at the crankshaft. Vee engines can be
mounted longitudinally (lengthwise) or transversely (sideways) in the
engine bay. A V6 will have two banks of 3 cylinders, a V8 two banks of 4
The angle of the "Vee" varies according to the number of cylinders. The
natural angle for a V4 and V8 is 90°. The natural angle for a V6 and V12
is 60° and for a V10 is 72°. Some manufacturers vary their angles due to
convenience or design requirements. Some manufacturers use 90° and
15° V6°s
Horizontally opposed
Horizontally opposed engines are commonly found in 2, 4, 6, and 12
cylinder configurations. Like a "Vee" engine, they have two banks, but in
this case they are 180° apart. Unlike "Vee" engines their crankshaft
differs in the way the pistons are paired. A Horizontally Opposed engine
is only fitted longitudinally.
Reproduced by Speciss College with permission from Kevin Sullivan -
Figure 3-2: Components of a four-stroke engine
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Figure 4-1: Four stroke cycle
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Chapter 4: Basic Function of Combustion Engines:
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SI (spark ignition) and CI (compression ignition) Engine
Basic SI 4-stroke principles
The five events of an internal combustion engine are Intake,
Compression, Ignition, Power, and Exhaust. In a 4-stroke gasoline
engine, the crankshaft does two revolutions in each engine cycle. Only
one of its 4-strokes delivers energy to the crankshaft.
The four strokes
1. The first step is to get the air-fuel mixture into the chamber. The
mixture is provided in older cars by single or multiple carburettors.
Nowadays cars have single- or most commonly multiple port fuel
injection. Mixture enters through an inlet port that is opened and
closed by an inlet valve. This is called Intake.
2. Next is compression. The piston compresses the air-fuel mixture into a
smaller volume.
A spark across the electrodes of a spark plug ignites it, and it burns.
This burning is called combustion.
3. The burning gases expand rapidly, and push the piston down the
cylinder until it reaches bottom dead centre.
The reciprocating action of the piston turns into the rotary motion of
the crankshaft.
4. The crankshaft forces the piston back up the cylinder, pushing leftover
gases out past an exhaust valve. And everything is back where it
started, ready to repeat the whole process.
The whole process is a cycle.
In one 4-stroke cycle, the crankshaft does 2 revolutions. In those 2
revolutions how many strokes does the piston make? It does 4 strokes.
In one 4-stroke cycle, only 1 stroke out of 4 delivers new energy to turn
the crankshaft.
Compression-ignition engine -CIBasic diesel engine components
Diesel engine parts are usually heavier or more rugged than those of
similar output gasoline engines. Their engine blocks and cylinder blocks
are usually made of cast iron.
Reproduced by Speciss College with permission from Kevin Sullivan -
Figure 4-2: Common Rail Diesel Injection System
Diesel engine passages
In a diesel engine, just air enters the combustion chamber first. It is then
highly compressed. Fuel is injected and ignites due to heat of the
compressed air. That's why diesels are called compression-ignition
Diesel fuel delivery
In direct injection fuel is injected directly into the combustion chamber. In
indirect injection fuel is sprayed into a smaller separate chamber in the
cylinder head. A glow plug helps the combustion start.
Valve arrangement
Most valves in diesels are parallel to the centre-line of the engine. Small
4-stroke engines usually have one inlet and one exhaust valve per
cylinder. Larger 4-stroke diesels may have two of each per cylinder.
Difference SI and CI Engines
Mechanically, 4 stroke diesel engines work identically to four-stroke petrol
engines in terms of piston movement and crank rotation. The differences
between them are found in the combustion cycle.
First, during the intake cycle, the engine only sucks air into the
combustion chamber through the intake valve - not a fuel/air mix.
Reproduced by Speciss College with permission from Kevin Sullivan -
Second, there is no spark plug. Diesel
engines work on self-ignition, or
detonation - the one thing you don't
want in a petrol engine! At the top of the
compression stroke, the air is highly
compressed (over 35 bar-), and very hot
(around 700 °C). The fuel is injected
directly into that environment and
because of the heat and pressure, it
spontaneously combusts. This system
is known as direct-injection. It gives the
characteristic knocking sound that
diesel engines make, and is also why
Figure 3-3: Compression ratio Petrol vs. Diesel
sometimes referred to as 'dieseling'.
Petrol engines typically run compression ratios around 10:1, with lower
end engines down as low as 8:1 and sportier engines up near 12:1.
Diesel engines on the other hand typically run around 14:1 compression
ratio and can go up as high as 25:1. Combined with the higher energy
content of diesel fuel (around 10 kW per litre compared to 8.23 kW per
litre of petrol), this means that the typical diesel engine is also a lot more
efficient than the petrol engine, hence the much higher fuel-mileage
Because of the design of the diesel engine, the injector is the most critical
part and has been subjected to hundreds of variations in both design and
position. It has to be able to withstand massive pressures and
temperatures, yet still deliver the fuel in a fine mist. One other component
that some diesel engines have is a glow-plug. From cold, some lowertech engines can't retard the ignition enough, or get the air temperature
high enough on start-up for the spontaneous combustion to happen. In
those engines, the glow-plug is a hot wire in the top of the cylinder
designed to increase the temperature of the compressed air to the point
at which the fuel will combust.
These engines typically have a pictograph on the dashboard that looks
like a light-bulb. When starting the engine cold, you need to wait for that
light to go out as the glow-plugs get up to temperature. In really old diesel
designs, this could be as long as 10 seconds. Nowadays it's nearly
instantaneous, or in the case of advanced ECM systems, not needed at
Reproduced by Speciss College with permission from Kevin Sullivan -
Chapter 5: Drive Line Assemblies
Figure 5-1: Rear wheel drive
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Figure 5-2: Front wheel drive
Figure 5-3: Four wheel drive
Figure 5-4: All wheel drive
Components of the Drive Line
The power of the engine must be send to the driving wheels. In vehicles
with a gear shift lever the power flow is from engine through the clutch
assembly. From there the manual transmission (gear box) alters the
speed ratio and the transferred torque. A propeller shaft (with rear wheels
driven vehicles) connects to the Final Drive (differential) and drive shafts
connect to the wheels.
Front wheel driven vehicles have the final drive enclosed in the gearbox
(transaxle) and connect to the driven wheels with drive shafts.
An auto electrician should recognized components of this power flow.
Numerous sensors and activators could be employed by modern vehicles
in the drive line.
Clutches: The clutch used in most light vehicle applications is a single
plate friction type. The clutch transmits torque from the engine to the
transmission and a release mechanism allows the driver to control the
flow of torque between them.
Gearbox layouts: In a manual transmission for a rear-wheel drive
Reproduced by Speciss College with permission from Kevin Sullivan -
vehicle, the gear train is built up on three shafts: the input shaft, the
countershaft, and the main shaft.
Transaxle designs In transaxle designs, the drive is transferred through
the clutch unit to a primary shaft. The primary shaft carries gears of
different sizes which mesh with gears on a secondary shaft.
Gearbox operation: The speed ratio and the torque transferred depend
on which gear is selected.
Automatic Transmissions
In an electronically controlled transmission, the speed of the vehicle and
the throttle opening are sensed by the vehicle speed sensor, and the
throttle position sensor.
The electronic control circuits attached of automatic transmissions are
complex. The control box is either separate or integrated in the ECU for
the engine management.
Final Drive & Drive Shafts
Rear-wheel final drives: In a conventional rear-wheel drive vehicle, a
crown wheel and pinion transfers the drive through ninety degrees and
provides a final gear reduction to the driving road wheels.
Front-wheel drive layout: In front-wheel drive vehicle layouts, the
engine can be mounted transversely or longitudinally. Drive is transmitted
to the front wheels through a transaxle.
Rear-wheel drive layout: In a conventional rear-wheel drive layout, the
engine and transmission are mounted longitudinally at the front of the
vehicle and drive is transmitted to a rear axle assembly by a propeller
Four-wheel drive layout: In a conventional four-wheel drive vehicle,
propeller shafts connect a transfer case at the rear of the transmission to
final drive units on both front and rear axles.
All-wheel drive layout: In a conventional full-time four-wheel drive
vehicle, a third differential is located in the transfer case.
4WD vs. AWD: All-wheel drive systems continuously power all four
wheels and provide maximum traction in all driving conditions. In a parttime system the driver manually shifts between two- and four-wheel
drive, and a part-time 4WD vehicle should not be driven on dry roads
when in 4WD mode.
Reproduced by Speciss College with permission from Kevin Sullivan -
Chapter 6: Auto Electrical Assemblies
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Modern vehicles incorporate many electrical and electronic components
and systems:
 Battery
 Charging System
 Starting System
 Ignition System (often embedded in Engine Management)
 Fuel injection System (often embedded in Engine Management)
 Engine Management
 Transmission control
 Braking and traction control
 Lights
 Head Lights, Position & Parking Lights
 Stop Lights
 Fog & Spot lights
 Signal System: Horn & Indicator, Hazard Light
 Electronic Suspension Control
 Supplemental Restraint System
Seat belt pre-tensioners
 Security Systems
 Remote control keys
 Theft deterrent
 Navigation (Global Positioning Satellites)
You need identify these electrical concepts and systems to effectively
troubleshoot them. Electrical and electronic system troubleshooting can
be straightforward if:
 You know what to look for.
 You know how to select and use the appropriate tools and test
Reproduced by Speciss College with permission from Kevin Sullivan -
Figure 6-1: Auto Electrical Assemblies
Chapter 7: Electrical Fundamentals
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General Electricity is a form of energy called electrical energy. It is
sometimes called an "unseen" force because the energy itself cannot be
seen, heard, touched or smelled. However, the effects of electricity can
be seen: a lamp gives off light; a motor turns; a cigarette lighter gets red
hot; a buzzer makes noise. The effects of electricity can also be heard,
felt, and smelled. A loud crack of lightning is easily heard, while a fuse
"blowing" may sound like a soft "pop" or "snap." With electricity flowing
through them, some insulated wires may feel "warm" and bare wires may
produce a "tingling" or, worse, quite a "shock." And, of course, the odour
of burned wire insulation is easily smelled.
Figure 7-1: Effects of electricity
Figure 7-2: Atomic structure
Reproduced by Speciss College with permission from Kevin Sullivan -
Electron Theory
Electron theory helps to explain electricity. The basic building block for
matter, anything that has mass and occupies space, is the atom. All
matter - solid, liquid, or gas - is made up of molecules, or atoms joined
together. These atoms are the smallest particles into which an element or
substance can be divided without losing its properties. There are only
about 100 different atoms that make up everything in our world. The
features that make one atom different from another also determine its
electrical properties.
Atomic Structure
Figure 7-3: Two different atoms
Figure 7-4: Balanced Atom
An atom is like a tiny solar system. The centre is called the nucleus,
made up of tiny particles called protons and
neutrons. The nucleus is surrounded by clouds of other tiny particles
called electrons. The electrons rotate about the nucleus in fixed paths
called shells or rings.
Hydrogen has the simplest atom with one proton in the nucleus and one
electron rotating around it. Copper is more complex with 29 electrons in
four different rings rotating around a nucleus that has 29 protons and 29
neutrons. Other elements have different atomic structures.
Reproduced by Speciss College with permission from Kevin Sullivan -
Atoms and Electrical Charges
Each atomic particle has an electrical charge. Electrons have a negative
(-) charge. Protons have a positive charge. Neutrons have no charge;
they are neutral.
In a balanced atom, the number of electrons equals the number of
protons. The balance of the opposing negative and positive charges holds
the atom together. Like charges repel, unlike charges attract. The positive
protons hold the electrons in orbit. Centrifugal force prevents the
electrons from moving inward. And the neutrons cancel the repelling force
between protons to hold the atom's core together.
Figure 7-5: Balanced –unbalanced atom
Figure 7-6: Free and bound electrons
Positive and Negative Ions
If an atom gains electrons, it becomes a negative ion. If an atom loses
electrons, it becomes a positive ion. Positive ions attract electrons from
neighbouring atoms to become balanced. This Causes the Electron Flow.
Electron Flow
The number of electrons in the outer orbit (valence shell or ring)
determines the atom's ability to conduct electricity. Electrons in the inner
rings are closer to the core, strongly attracted to the protons, and are
called bound electrons. Electrons in the outer ring are further away from
the core; less strongly attracted to the protons, and are called free
electrons. Electrons can be freed by forces such as friction, heat, light,
pressure, chemical action, or magnetic action. These freed electrons
move away from the electromotive force, or EMF ("electron moving
force"), from one atom to the next. A stream of free electrons forms an
electrical current.
Reproduced by Speciss College with permission from Kevin Sullivan -
Conductors, Insulators, Semiconductors
The electrical properties of various materials
are determined by the number of electrons in
the outer ring of their atoms.
• Conductors - Materials with 1 to 3 electrons
in the atom's outer ring make good conductors.
The electrons are held loosely, there's room for
more, and a low EMF will cause a flow of free
• Insulators - Materials with 5 to 8 electrons in
the atom's outer ring are insulators. The
electrons are held tightly, the ring is fairly full,
and a very high EMF is needed to cause any
electron flow at all. Such materials include
glass, rubber, and certain plastics.
• Semiconductors - Materials with exactly 4
electrons in the atom's outer ring are called Figure 7-7: Conductors, Insulators and
semiconductors. They are neither good Semiconductors
conductors, nor good insulators. Such materials include carbon,
germanium, and silicon.
Current Flow Theories
Two theories describe current flow.
The conventional theory, commonly used for
automotive systems, says current flows from (+) to
(-). Excess electrons flow from an area of high
potential to one of low potential (-).
The electron theory, commonly used for
electronics, says current flows from (-) to (+).
Excess electrons cause an area of negative
potential (-)
Figure 7-8: Current flow theories
and flow toward an area lacking electrons, an area
of positive potential (+), to balance the charges.
While the direction of current flow makes a difference in the operation of some
devices, such as diodes, the direction makes no difference to the three
measurable units of electricity: voltage, current, and resistance.
Reproduced by Speciss College with permission from Kevin Sullivan -
Terms of Electricity
Electricity cannot be weighed on a scale or measured into a container.
But, certain electrical "actions" can be measured.
These actions or "terms" are used to describe electricity; voltage,
current, resistance, and power.
Voltage is pressure - Current is flow. Resistance
opposes flow.
Power is the amount of work performed. It depends on the amount of pressure
and the volume of flow.
Voltage is electrical pressure, a potential force or difference in electrical
charge between two points. It can push electrical current through a wire,
but not through its insulation.
Voltage is measured in volts. One volt can push a certain amount of
current, two volts twice as much, and so on. A voltmeter measures the
difference in electrical pressure between two points in volts. A voltmeter
is used in parallel.
Figure 7-9: Voltage visualized
Current is electrical flow moving through a wire. Current flows in a wire pushed by
voltage. Current is measured in amperes, or amps, for short. An ammeter
measures current flow in amps. It is inserted into the path of current flow, or in
series, in a circuit.
Figure 7-10: Current visualized
Reproduced by Speciss College with permission from Kevin Sullivan -
Resistance opposes current flow. It is like electrical "friction." This resistance
slows the flow of current. Every electrical component or circuit has resistance.
And, this resistance changes electrical energy into another form of energy - heat,
light, motion.
Resistance is measured in Ohms. A special meter, called an ohmmeter, can
measure the resistance of a device in ohms when no current is flowing.
Figure 7-11: Resistance visualized
Factors Affecting Resistance
Five factors determine the resistance of conductors. These factors are
length of the conductor, diameter, temperature, physical condition and
conductor material. The filament of a lamp, the windings of a motor or
coil, and the bimetal elements in sensors are conductors. So, these
factors apply to circuit wiring as well as working devices or loads.
Electrons in motion are constantly colliding as voltage pushes them
through a conductor. If two wires are the same material and diameter, the
longer wire will have more resistance than the shorter wire. Wire
resistance is often listed in ohms per foot (e.g., spark plug cables at 5W
per foot). Length must be considered when replacing wires.
Large conductors allow more current flow with less voltage. If two wires
are the same material and length, the thinner wire will have more
resistance than the thicker wire. Wire resistance tables list ohms per foot
for wires of various thicknesses (e.g., size or gauge 1, 2, 3 are thicker
with less resistance and more current capacity; 18, 20, 22 are thinner with
more resistance and less current capacity). Replacement wires and
splices must be the proper size for the circuit current.
In most conductors, resistance increases as the wire temperature
increases. Electrons move faster, but not necessarily in the right direction.
Most insulators have less resistance at higher temperatures.
Reproduced by Speciss College with permission from Kevin Sullivan -
Semiconductor devices called thermistors have negative temperature
coefficients (NTC) resistance decreases as temperature increases. Most
EFI coolant temperature sensor has an NTC thermistor.
Physical Condition
Partially cut or nicked wire will act like smaller wire with high resistance in
the damaged area. A kink in the wire, poor splices, and loose or corroded
connections also increase resistance. Take care not to damage wires
during testing or stripping insulation.
Materials with many free electrons are good conductors with low
resistance to current flow. Materials with many bound electrons are poor
conductors (insulators) with high resistance to current flow. Copper,
aluminium, gold, and silver have low resistance; rubber, glass, paper,
ceramics, plastics, and air have high resistance.
Figure 7-12: Factors influencing the resistance
Voltage, Current and Resistance in Circuits
A simple relationship exists between voltage, current, and resistance in
electrical circuits. Understanding this relationship is important for fast,
accurate electrical problem diagnosis and repair.
Figure 7-13: Ohm’s law
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Ohm's Law
Ohm's Law says: The current in a circuit is directly proportional to the
applied voltage and inversely proportional to the amount of resistance.
This means that if the voltage goes up, the current flow will go up, and
vice versa. Also, as the resistance goes up, the current goes down, and
vice versa.
Figure 7-14: Memory aid to apply Ohm’s Law formula
Ohm's Law can be put to good use in electrical troubleshooting. But,
calculating precise values for voltage, current, and resistance is not
always practical -nor, really needed. A more practical, less timeconsuming use of Ohm's Law would be to simply apply the concepts
Source Voltage is not affected by either current or resistance. It is either
too low, normal, or too high. If it is too low, the current will be low. If it is
normal, current will be high if resistance is low or current will be low if
resistance is high. If voltage is too high, the current will be high.
Current is affected by either voltage or resistance. If the voltage is high or
the resistance is low, current will be high. If the voltage is low or the
resistance is high, current will be low.
Resistance is not affected by either voltage or current. It is either too low,
okay, or too high. If resistance is too low, the current will be high at any
voltage. If resistance is too high, the current will be low if voltage is okay.
Electric Power and Work
Voltage and current are not measurements of electric power and work.
Power, in watts, is a measure of electrical energy. Power (P) equals
current in amps (1) times voltage in volts (E), P = I x E. Work, in wattseconds or watt-hours, is a measure of the energy used in a period of
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time. Work equals power in wafts (W) times time in seconds (s) or hours
(h), W = P x time. Electrical energy performs work when it is changed into
thermal (heat) energy, radiant (light) energy, audio (sound) energy,
mechanical (motive) energy, and chemical energy. It can be measured
with a watt-hour meter.
Actions of Current
Current flow has the following effects; motion, light or heat generation, chemical
reaction, and electromagnetism.
Heat Generation
When current flows through a lamp filament, defroster grid, or cigarette lighter,
heat is generated by changing electrical energy to thermal energy. Fuses melt
from the heat generated when too much current flows.
Chemical Reaction
In a simple battery, a chemical reaction between two different metals and a
mixture of acid and water causes a potential energy, or voltage. When the battery
is connected to an external load, current will flow. The current will continue
flowing until the two metals become similar and the mixture becomes mostly
When current is sent into the battery by an alternator or a battery charger,
however, the reaction is reversed. This is a chemical reaction caused by current
flow. The current causes an electrochemical reaction that restores the metals and
the acid-water mixture.
Electricity and magnetism are closely related. Magnetism can be used to produce
electricity. And, electricity can be used to produce magnetism. All conductors
carrying current create a magnetic field. The magnetic field strength is changed
by changing current - stronger (more current), weaker (less current). With a
straight conductor, the magnetic field surrounds it as a series of circular lines of
force. With a looped (coil) conductor, the lines of force can be concentrated to
make a very strong field. The field strength can be increased by increasing the
current, the number of coil turns, or both. A strong electromagnet can be made by
placing an iron core inside a coil. Electromagnetism is used in many ways.
Types of Electricity
There are two types of electricity: static and dynamic. Dynamic electricity can be
either direct current (DC) or alternating current (AC).
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Figure 7-15: Types of Electricity
Static Electricity
When two non conductors are rubbed together, some electrons are freed. Both
materials become electrically charged. One is lacking electrons and is positively
charged. The other has extra electrons and is negatively charged. These charges
remain on the surface of the material and do not move unless the two materials
touch or are connected by a conductor. Since there is no electron flow, this is
called static electricity.
Dynamic Electricity
When electrons are freed from their atoms and flow in a material, this is called
dynamic electricity. If the free electrons flow in one direction, the electricity is
called direct current (DC). This is the type of current produced by the vehicle's
battery. If the free electrons change direction from positive to negative and back
repeatedly with time, the electricity is called alternating current (AC). This is the
type of current produced by the vehicle's alternator. It is changed to DC for
powering the vehicle's electrical system and for charging the battery.
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Chapter 8: Digital Multimeters Back to ToC
Introduction to Digital Multimeters
With the introduction of oxygen sensors into the
fuel control systems of vehicles in the early 1980s,
we were also introduced to the use of digital
multimeters. These early meters were bulky and
relatively expensive, when compared to analogue
Digital multimeters are now fairly commonplace.
With DMMs available at about the same price as
analogue meters, the DMM is definitely the best
measurement tool for general electrical diagnosis.
The advantages to using a DMM over an
analogue meter are:
 Easier to use:
 Auto-ranging" meters self-adjust to the range
needed for a specific measurement. This is Figure 8-1: Quality digital
particularly helpful when measuring resistance multimeter
 Accuracy: Because of the high internal resistance (or high impedance)
of most DMMs, the accuracy of the meter is increased.
 Not sensitive to polarity: When using the voltmeter, the probes can be
connected in reverse polarity without affecting the accuracy of the
reading or damaging the meter. The meter will indicate this reverse
polarity condition by placing a ―−" symbol in the display.
 Durability: Most good quality meters can withstand a substantial
amount of shock without damage.
 Long battery life: Batteries can last in excess of 200 service hours on
DMMs. Some models also have an automatic shut-off feature.
Many good quality DMMs have additional features that can be helpful
when diagnosing difficult problems:
 ―Min-Max": Holds in memory a maximum or minimum voltage or
amperage value measured over a period of time. This is extremely
helpful to identify a problem such as an intermittent +B or ground
 Analogue Bar Graph: Most digital displays refresh or update about 2
times a second.
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While DMMs have a lot of useful features to help you in diagnosing
electrical problems, one major drawback is that these meters are not
necessarily user-friendly. Learning to read the meter and use its features
requires practice.
Digital Voltmeter
The most frequently used feature of a DMM is the voltmeter. A voltmeter
is useful to determine if there is voltage present at specific points in the
circuit when diagnosing open circuit problems. By applying the series
circuit voltage drop concept, it can also be used to quickly isolate the
location of any high circuit resistance problem.
Measuring Open Circuit Voltage or Pin Voltage
Measuring Open Circuit Voltage or Pin Voltage:
1. Connect the negative probe to ground at the component ground
terminal or to a known good ground.
2. Connect the positive probe to the pin you want to inspect
 If the meter is auto-ranging, fix the display to show only 1 decimal
point. If the meter is non auto-ranging, use the 20V range.
 Remember that an open circuit voltage measurement tells you only if
there is a connection to B+; it DOES NOT tell you how much
resistance there is in the connection or circuit.
Figure 8-2: Measuring Open Circuit Voltage
This inspection can be made by back-probing the terminal or from the front with the connector disconnected.
If you have to probe from the front of the connector, NEVER insert the test probe into a female terminal
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Voltage Drop Measurement
A voltage drop measurement is taken dynamically while the circuit is in
1.Turn the circuit ON.
2.Connect the positive and negative probes of the meter in parallel to the
component or section of the circuit you want to check.
• By using the electrical wiring diagram (EWD), you can isolate portions
of the circuit and check for unwanted resistances.
• A measurement of 0 Volts can indicate two different conditions:
a. There is virtually no resistance in the part of the circuit you are
b. The circuit is OFF or open; no current flow.
Figure 8-3: Measuring Voltage Drop:
Connect the voltmeter in parallel to the part of the circuit you want to
check by back-probing the connector.
Remember the load should be getting about the same as battery voltage
This is the most accurate way to detect a problem
resistance in high amperage (above 3 or 4 amps) circuits. In
these circuits, even a resistance of 1W or less can have a big effect on
the load. Because the test is done while the circuit is operating, factors
such as the amount of current flow and the heat generated will be taken
into account.
Digital Ammeter
Because Repair Manual and EWD specifications are usually in volts, the
ammeter is not frequently used as a tool in body electrical diagnosis. It
can, however, be a very effective tool.
The ammeter is typically used in:
1. Starting and Charging System inspection
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2. Diagnosing parasitic load problems. A parasitic load is sometimes
referred to as a ‖draw", something that drains the battery while the car
is parked overnight.
The ammeter can be used to dynamically test the condition of a circuit.
But because amperage specs are not found in the RM or EWD for most
circuits, and because ammeters
cannot pinpoint the location of a
problem like a voltmeter can, it is
not frequently used in body
electrical diagnosis.
Figure 8-4: Diagnosing with an Ammeter
For the fuel pump, an ammeter can be put in series at
the +B and Fp terminal (key ON, engine OFF).
This operates the fuel pump and lets you check the
amount of amperage the fuel pump is drawing.
Compare this reading to a known good vehicle.
If a component in a circuit is particularly difficult to
access (such as the electric fuel pump), an amperage
measurement of the circuit can be a good indicator of the circuit’s
condition. Because there are no specs given for this circuit, you will
need to measure the amperage draw of the same circuit on a known
good vehicle, and compare the readings to determine if you have a
Types of Digital Ammeter
Figure 8-5: Accessory type of “clamp-on” ammeters
are expensive
There are two types of ammeters: a series type and clamp type.
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A series type ammeter is the type of meter that is built into every DMM.
This meter is designed to measure relatively small current flows (below
10A). Most meters measure in either milliamps (mA) or Amps (A). Before
connecting the meter into the circuit, make sure the circuit draw is within
what your meter can handle.
It is a good practice to initially set the meter to the highest range
available, and lower the range while the current is being measured. Most
ammeters are fuse protected to prevent damage from short-to-grounds or
overload conditions. The series type ammeter is best suited for
measuring current flows below 1A. Clamp type ammeters are used for
years on starting/charging system testers such as the Sun VAT− 40/60.
This type of ammeter is also available as an accessory that you can use
with any DMM.
Digital Ohmmeter
Figure 8-6: Digital Ohmmeter Display
If you are using the meter in auto-ranging mode, be
sure to look at the units (KΩ or Ω) at the side of the
display or on the range selection knob.
An ohmmeter measures the amount of electrical resistance between two
points. The digital ohmmeter has several significant advantages over its
analogue counterpart:
• Easier to read
• “Zero" resets automatically
• Extremely accurate
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Additional Features - Diode Check
When connecting an ohmmeter, make sure that the circuit or component
is isolated from parallel branches or other voltage sources. Most good
quality meters are ―forgiving" when accidentally connected to voltage, but
analogue meters and low priced DMMs may not be.
In the past, an ohmmeter was commonly used to check diodes. The
operation of the diode could be verified by checking for continuity in one
direction, and for no continuity in the other. However, the voltage that a
digital ohmmeter uses to make its resistance measurement is usually less
than 0.2V. This low voltage is not enough to ―forward bias" the diode, so
the diode will show no continuity in either direction.
Most good quality DMMs have a diode check function. This
function (on the better meters) will tell you the forward bias voltage drop
of the diode - the amount of voltage required to turn ON the diode so that
current will flow through it. For the silicon diodes found on the car, this
voltage should be around 0.5V.
In some low priced meter‘s the diode check function does not measure
the forward bias voltage drop. Instead, these meters simply raise the
voltage used by the ohmmeter to allow a check for continuity in one
direction and no continuity in the other. The number on the display is not
a voltage drop.
Additional Features - Audible Continuity Beep
When working under the instrument panel or in an area where the face of
the meter is not easily visible, the audible continuity beep is helpful. The
specifications for this feature vary between meter manufacturers.
Most meters will ―beep" whenever there is a less than a specified amount
of resistance measured. (This can mean within double the range selected
or could be just 5 − 10% of the range selected on the meter.) On many
meters, the ―beep" feature also works with the voltmeter.
Ohmmeter Common Mistakes
• Zero Ohms: Don‘t confuse 0 Ω with ∞ or OL, An infinite amount of
resistance means that there is an OPEN in the circuit no current flow can
get through. Zero ohms indicates perfect continuity, no resistance to
current flow.
• Placement of the Decimal Point: Auto-ranging meters automatically
change the display from ohms (Ω) to kilo ohms (KΩ).
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Figure 8-7: Using an Ohmmeter
Make sure the ohmmeter is isolated from voltage, and from parallel branches that
shunt around the area you want to check.
Never test an ECU directly with an ohmmeter. The
measurement made will be inconclusive at best, and
could cause damage. The correct method for using the ohmmeter is
shown in the diagram here.
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Chapter 9: General Electrical System Diagnosis
Electrical diagnostic techniques
Back to ToC
Figure 9-1: Diagnostic Flow Chart
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Check the obvious first!
Start all hands-on diagnostic routines with ‗hand and eye checks‘. In
other words look over the vehicle for obvious faults. For example, if the
battery terminals are loose or corroded then put this right before carrying
out complicated voltage readings. Here are some further suggestions that
will at some point save you a lot of time.
● A misfire may be caused by a loose plug lead – it is easier to look for
this than interpret the ignition waveforms on a scope.
● If the ABS warning light stays on – look to see if the wheel speed
sensor(s) are covered in mud or oil.
Test lights and analogue meters – warning!
A test lamp is ideal for tracing faults in say a lighting circuit because it will
cause a current to flow which tests out high resistance connections.
However, it is this same property that will damage delicate electronic
circuits – so don‘t use it for any circuit that contains an electronic control
unit (ECU). Even an analogue voltmeter can cause enough current to flow
to at best give you a false reading and at worst damage an ECU – so
don‘t use it! A digital multimeter is ideal for all forms of testing. Most have
an internal resistance in excess of 10MΩ. This means that the current
they draw is almost insignificant. An LED test lamp or a logic probe is also
Generic electrical testing procedures
The following procedure is very generic but with a little adaptation can be
applied to any electrical system. Refer to manufacturer‘s
recommendations if in any doubt. The process of checking any system
circuit is broadly as follows.
Volt drop testing
Volt drop is a term used to describe the difference between two points in
a circuit. In this way we can talk about a voltage drop across a battery
(normally about 12.6 V) or the voltage drop across a closed switch
(ideally 0 V but may be 0.1 or 0.2 V).
The first secret to volt drop testing is to remember a basic rule about a
series electrical circuit:
The sum of all volt drops around a circuit always adds up to
the supply.
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The second secret is to ensure that the circuit is switched
on and operating – or at least the circuit should be ‗trying
to operate‘!
Figure 9-2: Voltage Drop Testing
In figure 9-2 this means that V1 + V2 + V3 = Vs. If the battery voltage
measures say 12V when electrical testing a reading of less than 12 V at
V2 would indicate a volt drop between the terminals of V1 and/or V3.
Likewise the correct operation of the switch, that is it closes and makes a
good connection, would be confirmed by a very low reading on V1.
What is often described as a ‗bad earth‘ (what is meant is a high
resistance to earth), could equally be determined by the reading on V3.
To further narrow the cause of a volt drop down a bit, simply measure
across a smaller area. The voltmeter V4, for example, would only
assess the condition of the switch contacts.
Testing for short circuits to earth
This fault will normally blow a fuse – or burn out the wiring completely! To
trace a short circuit is very different from looking for a high resistance
connection or an open circuit. The volt drop testing above will trace an
open circuit or a high resistance connection. A good method of tracing a
short, after looking for the obvious signs of trapped wires, is to connect a
bulb or test lamp across the blown fuse and switch on the circuit. The
bulb will light because on one side it is connected to the supply for the
fuse and on the other side it is connected to earth via the fault. Now
disconnect small sections of the circuit one at a time until the test lamp
goes out. This will indicate the particular circuit section that has shorted
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On and off load tests
‗On load‘ means that a circuit is drawing a current. Off load means it is
not! One example where this may Battery voltage may be 12 V off load
but only 9 V when on load.
A second example is the supply voltage to the positive terminal of an
ignition coil via a high resistance connection (corroded switch terminal for
example). With the ignition on and the vehicle not running, the reading will
almost certainly be battery voltage because the ignition ECU switches off
the primary circuit and no volt drop will show up. However, if the circuit
were switched on (with a fused jumper lead if necessary) a lower reading
would result showing up the fault.
Figure 9-3: System Block Diagram
Black box technique
The technique that will be covered here is known as ‗black box
faultfinding‘. This is an excellent technique and can be applied to many
vehicle systems from engine management and ABS to cruise control and
As most systems now revolve around an ECU, the ECU is considered to
be a ‗black box‘, in other words we know what it should do but how it does
it is irrelevant. The figure on the right shows a block diagram that could be
used to represent any number of automobile electrical or electronic
systems. In reality the arrows are wires from the ‗inputs‘ to the ECU and
from the ECU to the ‗outputs‘. Treating the ECU as a ‗black box‘ allows us
to ignore its complexity. The theory is that if all the sensors and
associated wiring to the ‗black box‘ are OK, all the output actuators and
their wiring are OK and the supply/earth connections are OK, then the
fault must be the ‗black box‘. Most ECUs are very reliable, however, and it
is far more likely that the fault will be found in the inputs or outputs.
Normal faultfinding or testing techniques can be applied to the sensors
and actuators. For example, if an ABS system uses four inductive type
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wheel speed sensors, then an easy test is to measure their resistance.
Even if the correct value were not known, it would be very unlikely for all
four to be wrong at the same time so a comparison can be made. If the
same resistance reading is obtained on the end of the sensor wires at the
ECU then almost all of the ‗inputs‘ have been tested with just a few
ohmmeter readings.
The same technique will often work with ‗outputs‘. If the resistance of all
the operating windings in say a hydraulic modulator were the same, then
it would be reasonable to assume the figure was correct.
Sometimes, however, it is almost an advantage not to know the
manufacturer‘s recommended readings. If the ‗book‘ says the value
should be between 800 and 900Ω, what do you do when your ohmmeter
reads 905Ω?
Finally, don‘t forget that no matter how complex the electronics in an
ECU, they will not work without a good power supply and an earth!
Chapter 10: Circuit Protection
Back to ToC
Figure 10-1: Circuit with fuse
Circuit protection
Circuit protection devices are used to protect wires and connectors from
being damaged by excess current flow caused by an over current or
short-circuit. Excess current causes excess heat, which causes circuit
protection to "open circuit".
Figure 10-2: Visible check of
blown fuse
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Figure 10-3: various circuit protection elements
Circuit protection devices
Fuses, fuse elements, fusible links, and circuit breakers are used as
circuit protection devices. Circuit protection devices are available in a
variety of types, shapes, and specific current ratings.
A fuse is the most common protection device. A fuse is placed in an
electrical circuit, so that when current flow exceeds the rating of the fuse it
"blows" or "blows out". The element in the fuse melts, opening the circuit
and preventing other components of the circuit from being damaged by
the over-current. The size of the metal fuse element determines the
rating. Remember excessive current causes excess heat, and it is heat
and not the current that causes the circuit protector to open. Once a fuse
"blows" it must be replaced with a new one.
Fuse locations
Fuses are located throughout the entire vehicle. Common locations
include the engine Compartment, behind the left or right kick panels, or
under the dash. Fuses are usually grouped together and are often mixed
in with other components like relays, circuit breakers and fuse elements.
Fuse block covers
Fuse / relay block covers usually label the location and position of each
fuse, relay, and fuse element contained within.
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Fuse types
Fuses are classified into basic categories: blade type fuses or cartridge
type fuses. Several variations of each are used.
Common fuse types
The blade fuse and fuse element are by far the most commonly used
today. Three different types of blade fuses exist: the maxi fuse, the
standard ATO fuse, and the mini fuse. The fuse element has replaced the
fusible link and will be explained later.
Basic Construction
The blade type fuse is a compact design with a metal element and
transparent insulating housing which is colour-coded for each current
rating. (Standard ATO shown below: however construction of both the
mini and maxi fuses are the same.)
Fuse Amperage Colour Rating
Fuse amperage colour ratings for both the mini and standard ATO fuses
are identical. However, the amperage colour ratings of maxi fuses use a
different colour scheme.
Colour Ratings for STANDARD and MINI Fuses Colour Ratings For MAXI Fuses
Identification Colour
Fuse Amp Rating
Identification Colour
Older Type Fuses
Many older vehicles, both foreign and domestic, use glass or ceramic
fuse cartridges that were either colour coded or stamped on case for
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current ratings. Glass fuses were used on older domestic vehicles while
the ceramic were used on most of the older European vehicles.
Ceramic fuses have an amperage colour rating system while glass fuses
have the amperage ranging stamped into one of the metal end caps.
Fusible Links And Fuse Elements
Fusible links are divided into two categories: the fuse element cartridge
and the fusible link. The construction and function of fusible links and fuse
elements are similar to that of a fuse.
The main difference is that the fusible link and fuse element are used to
protect higher amperage electrical circuits, generally circuits 30 amps or
higher. As with fuses, once a fusible link or fuse element blows out, it
must be replaced with a new one.
Figure 10-5: Glass fuses, fusible links, fuse elements and their construction
Fuse Element Cartridge
Fuse elements, a cartridge type fusible link, are also known as a Pacific
fuses. The element has the terminal and fusing portion as a unit. Fuse
elements have replaced fusible links for the most part. The housing is
colour coded for each current rating. Although, fuse elements are
available in two physical sizes and are either plug in or bolt on design, the
plug-in type is the most popular.
Fuse Element Cartridge Construction
Construction of the fuse element is quite simple. A coloured plastic
housing contains the fusing portion element which can be viewed through
a clear top. Fuse ratings are also stamped on the case.
Fuse Element Colour Identification
Fuse amperage colour ratings are shown below. The fusing portion of the
fuse element is visible through a clear window. The amperage ratings are
also listed on the fuse element.
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Fuse Element Colour Ratings – Pacific
Figure 10-6: ‘Pacific’ fuse element
Identification Colour
Fusible Links
Fusible links are short pieces of a smaller
diameter wire designed to melt during an over current condition. A fusible
link is usually four (4) wire sizes smaller than the circuit that it is
protecting. The insulation of a fusible link is a special non-flammable
material. This allows the wire to melt, but the insulation to remain intact
for safety. Some fusible links have a tag at one end that indicates its
rating. Like fuses, fusible links must be replaced after they have "blown"
or melted opened. Many manufacturers have replaced fusible links with
fuse elements or maxi fuses.
Figure 10-8: Construction and reset of manual
circuit breaker
Figure 10-7: Examples of circuit
Circuit Breakers
Circuit breakers are used in place of fuses for the protection of
complicated power circuits such as the power windows, sunroofs and
heater circuits. Three types of circuit breakers exist: The manual reset
type - mechanical, the automatic resetting type - mechanical, and the
automatically reset solid state type - PTC. Circuit breakers are usually
located in relay/fuse boxes; however, some components like power
window motors have circuit breakers built in.
Circuit Breaker Operation (Manual Type)
The circuit breaker contains a metal strip made of two different metals
bonded together called a bimetal strip. This strip is in the shape of a disc
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and is concaved downward. When heat from the excessive current is
higher than the circuit breaker current rating the two metals change shape
unevenly. The strip bends or warps upwards and the contacts open to
stop current flow. The circuit breaker can be reset after it is tripped.
Automatic Resetting Type - Mechanical
Circuit breakers that automatically reset are called "cycling" circuit
breakers. This type of circuit breaker is used to protect high current
circuits, such as power door locks, power windows, air conditioning, etc.
The automatically resetting circuit breaker contains a bimetal strip. The
bimetal strip will overheat and open from the excess current by an overcurrent condition and is automatically reset when the temperature of the
bimetal strip cools.
Figure 10-9: “Cycling” automatic
resetting circuit breaker
Chapter 11: Wire Repair
Back to ToC
Figure 11-1: Different types of cables
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Conductors are needed to complete the path for electrical current to flow
from the power source to the working devices and back to the power
Power or Insulated Conductors
Conductors for the power or insulated current path may be solid wire,
stranded wire, or printed circuit boards. Solid, thin wire can be used when
current is low. Stranded, thick wire is used when current is high. Printed
circuitry - copper conductors printed on an insulating material with
connectors in place - is used where space is limited, such as behind
instrument panels.
Special wiring is needed for battery cables and for ignition cables. Battery
cables are usually very thick, stranded wires with thick insulation. Ignition
cables usually have a conductive carbon core to reduce radio
Figure 11-2: Earth return system –commonly
MINUS connected to ground (earth)
Ground Paths
Wiring is only half the circuit in automotive electrical systems. This is
called the "power" or insulated side of the circuit. The other half of the
path for current flow is the vehicle's engine, frame, and body. This is
called the ground side of the circuit. These systems are called single-wire
or ground-return systems. A thick, insulated cable connects the battery's
positive ( + ) terminal to the vehicle loads. As insulated cable connects
the battery's negative ( - ) cable to the engine or frame. An additional
grounding cable may be connected between the engine and body or
Resistance in the insulated side of each circuit will vary depending on the
length of wiring and the number and types of loads. Resistance on the
ground side of all circuits must be virtually zero. This is especially
important: Ground connections must be secure to complete the circuit.
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Loose or corroded ground connections will add too much resistance for
proper circuit operation.
System Polarity
System polarity refers to the connections of the positive and negative
terminals of the battery to the insulated and ground sides of the electrical
system. On most vehicles, the positive (+) battery terminal is connected to
the insulated side of the system. This is called a negative ground system
having positive polarity.
Knowing the polarity is extremely important for proper service. Reversed
polarity may damage alternator diodes, cause improper operation of the
ignition coil and spark plugs, and may damage other devices such as
electronic control units, test meters, and instrument panel gauges.
Harnesses are bundles of wires that are grouped together in plastic
tubing, wrapped with tape, or moulded into a flat strip. The coloured
insulation of various wires allows circuit tracing. While the harnesses
organize and protect wires going to common circuits, do not over look the
possibility of a problem inside.
Figure 11-3: Wiring harness
Figure 11-4: Wiring connectors and handling tips
Wire Insulation
Conductors must be insulated with a covering or "jacket." This insulation
prevents physical damage, and, more important, keeps the current flow in
the wire. Various types of insulation are used depending on the type of
conductor. Rubber, plastic, paper, ceramics, and glass are good
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Various types of connectors, terminals, and junction blocks are used on
Modern vehicles. The wiring diagrams identify each type used in a circuit.
Connectors make excellent test points because the circuit can be
"opened" without need for wire repairs after testing. However, never
assume a connection is good simply because the terminals seem
connected. Many electrical problems can be traced to loose, corroded, or
improper connections. These problems include a missing or bent
connector pin.
Connector Repair
The repair parts now in supply are limited to those connectors having
common shapes and terminal cavity numbers. Therefore, when there is
no available replacement connector of the same shape or terminal cavity
number, please use the alternative method described below. Make sure
that the terminals are placed in the original order in the connector
cavities, if possible, to aid in future diagnosis.
When a connector with a different number of terminals than the original
part is used, select a connector having more terminal cavities than
required, and replace both the male and female connector parts.
Example: You need a connector with six terminals, but the only
replacement available is a connector with eight terminal cavities.
Replace both the male and female connector parts with the eight
terminal part, transferring the terminals from the old connectors to the
new connector.
Conductor Repair
Conductor repairs are sometimes needed because of wire damage
caused by electrical faults or by physical abuse. Wires may be damaged
electrically by short circuits between wires or from wires to ground.
Fusible links may melt from current overloads. Wires may be damaged
physically by scraped or cut insulation, chemical or heat exposure, or
breaks caused during testing or component repairs.
Figure 11-5: Typical wiring defects
Figure 11-6: American wire gauge table
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Wire Size
Choosing the proper size of wire is critical when making circuit repairs.
While choosing wires too thick for the circuit will only make splicing a bit
more difficult, choosing wires too thin may limit current flow to
unacceptable levels or even results in melted wires. Two size factors
must be considered: wire gauge number and wire length.
Wire Gauge Number
Wire gauge numbers are determined by the conductor's cross-section
area. In the American Wire Gauge system, "gauge" numbers are
assigned to wires of different thicknesses. While the gauge numbers are
not directly comparable to wire diameters and cross-section areas, higher
numbers (16, 18, 20) are assigned to increasingly thinner wires and lower
numbers (1, 0, 2/0) are assigned to increasingly thicker wires. The chart
shows AWG gauge numbers for various thicknesses.
Wire cross-section area in the AWG
system is measured in circular mils. A mil
is a thousandth of an
inch (0.001). A circular mil is the area of
a circle 1 mil (0.001) in diameter.
In the metric system used worldwide,
wire sizes are based on the crosssection area in square millimetres (mm2). Figure 11-7: Comparison wire size AWG and
These are not the same as AWG sizes in
circular mils. The chart shows AWG size equivalents for various metric
Wire Length
Wire length must be considered when repairing circuits because
resistance increases with longer lengths. For instance, a 1 mm2 (16gauge) wire can carry an 18-amp load for 3 meters without excessive
voltage drop.
But, if the section of wiring being replaced is only 1 meter long, a 0.8 mm2
(18-gauge wire) can be used. Never use a heavier wire than necessary,
but - more important - never use a wire that will be too small for the load.
Wire Repairs
• Cut insulation should be wrapped with tape or covered with heat-shrink
tubing. In both cases, overlap the repair about 12 mm on either side. • If
damaged wire needs replacement, make sure the same or larger size is
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used. Also, attempt to use the same colour. Wire strippers will remove
insulation without breaking or nicking the wire strands.
• When splicing wires, make sure the battery is disconnected. Clean the
wire ends. Crimp and solder them using resin-core, not acid-core, solder.
Figure 11-8:
stripping tool
Figure 11-9: Soldering iron.
Shown is a ‘soldering gun’
Figure 11-10: Properly tinned
solder iron tip
Soldering joins two pieces of metal together with a lead and tin alloy. In
soldering, the wires should be spliced together with a crimp. The less
solder separating the wire strands, the stronger is the joint.
Solder is a mixture of lead and tin plus traces of other substances. Flux
core wire solder (wire solder with a hollow centre filled with flux) is
recommended for electrical splices.
Soldering heats the wires. In so doing, it accelerates oxidization, leaving a
thin film of oxide on the wires that tend to reject solder. Flux removes this
oxide and prevents further oxidation during the soldering process.
Resin-type flux must be used for all electrical work. The residue will not
cause corrosion, nor will it conduct electricity.
The soldering iron should be the right size for the job. An iron that is too
small will require excessive time to heat the work and may never heat it
properly. A low-wattage (25-100 W) iron works best for wiring repairs.
All traces of paint, rust, grease, and scale must be removed. Good
soldering requires clean, tight splices.
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The soldering iron tip is made of copper. Through the solvent action of
solder and prolonged heating, it will pit and corrode. An oxidized or
corroded tip will not satisfactorily transfer heat from the iron to the work. It
should be cleaned and tinned. Use a file and dress the tip down to the
bare copper. File the surfaces smooth and flat.
Then, plug the iron in. When the tip colour begins to change to brown and
light purple, dip the tip in and out of a can of soldering flux (resin type).
Quickly apply rosin core wire solder to all surfaces.
The iron must be at operating temperature to tin properly. When the iron
is at the proper temperature, solder will melt quickly and flow freely.
Never try to solder until the iron is properly tinned.
Apply the tip flat against the splice. Apply rosin-core wire solder to the flat
of the iron where it contacts the splice. As the wire heats, the solder will
flow through the splice.
1. Clean wires.
2. Wires should be crimped together.
3. Iron must be the right size and must be hot.
4. Iron tip must be tinned.
5. Apply full surface of soldering tip to the splice.
6. Heat wires until solder flows readily.
7. Use rosin-core solder.
8. Apply enough solder to form a secure splice.
9. Do not move splice until solder sets.
10. Place hot iron in a stand or on a protective pad.
11. Unplug iron as soon as you are finished.
Figure 11-11: Properly soldering
of splice connection
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Figure 11-12: Wiring colour coding
Chapter 12: The Battery
Back to ToC
The battery is the main source of electrical
energy on all vehicles.
The battery powers these major electrical
 Starting
 Ignition
 Charging
 Lighting
 Accessories
Battery Functions
Figure 12-1: Standard Automotive Battery
Engine off − the battery provides energy to operate lighting and
Engine starting − the battery provides energy to operate the starter
motor and ignition system during starting.
Engine running − the charging system provides most of the energy
required with the engine running; the battery acts as a voltage stabilizer to
protect voltage sensitive circuits, particularly digital circuits.
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Battery Type
Lead-Acid − virtually all automotive batteries are lead-acid batteries. Two
different metals, both lead compounds, are immersed in an acid
electrolyte. The chemical reaction produced provides electrical energy.
Low Maintenance/No Maintenance − some manufacturers use this
terminology. ―Low maintenance" means that electrolyte can be added.
―No maintenance" means that the battery is sealed.
Vented − Most batteries have removable vented caps that are used to
check electrolyte level and add distilled water as necessary to restore the
level. The caps also allow hydrogen gas, a by-product of battery charging,
to escape during charging.
Sealed − some lead-acid batteries are
sealed, that is, there are no removable caps
to check electrolyte or replenish it. Some of
these batteries have a small ―eye" to
indicate charge level. Still others are sealed,
but include connections to external vent
Battery Construction
Battery Case
The battery case and cover...
Figure 12-2: Lead-acid batteries are called
by different names: vented, sealed, low
- form a sealed container.
maintenance, and no maintenance.
- protect the internal parts.
- keep the internal parts in proper
- prevent electrolyte leakage
Two types of plates are used in a battery: positive and negative.
Positive − Positive plates are made of antimony covered with an active
layer of lead dioxide (PbO2).
Negative − Negative plates are made of lead covered with an active layer
of sponge lead (Pb).
Only the surface layers on both plates take part in the chemical reaction.
Plate surface area − As the surface area of the plates increases, so
does the current capacity of the battery. Surface area is determined by
the size of each plate, as well as the total number of plates in a battery.
Generally speaking, the larger the battery, the higher is its current
Surface area has no effect on battery voltage.
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Separators The plates are separated by thin porous insulators. These
allow electrolyte to pass freely between the plates, but prevent the plates
from touching each other and shorting out.
Insulators Insulator plates keep positive and negative plates from
touching each other and shorting out. Battery Cells A typical lead acid
battery is organized into cells.
Each cell:
• Consists of multiple positive and negative plates immersed in their own
electrolyte reservoir.
• Produces about 2.1 volts, regardless of battery size.
Automotive batteries are rated at 12 volts. To make up this voltage, six
cells, each producing 2.1 volts, are connected in series.
6 x 2.1 volts = 12.6 volts
As a result, actual battery voltage is typically closer to 12.6 volts.
Cells are connected in series with heavy internal straps.
A positive and a negative terminal post provide connection points for the
vehicle‘s battery cables.
Venting System
On some batteries, vent caps allow a
controlled release of hydrogen gas.
This gas forms naturally during battery
recharging, whether by the vehicle‘s
alternator or by an external charger.
The electrolyte is a mixture of sulfuric
acid (H2SO4) and water (H2O). The
Figure: 12-3: Venting System
electrolyte reacts chemically with the
active material on the plates to produce a voltage (electrical pressure).
How Batteries Work
The function of a lead acid cell is based on a simple chemical reaction.
When two dissimilar metals are immersed in an acid solution, a chemical
reaction produces a voltage. Using this reaction, a lead-acid battery can
be discharged and charged many times.
There are four stages in the discharging-charging cycle:
Fully Charged
• Positive plate covered with lead oxide (PbO2).
• Negative plate covered with sponge lead (Pb).
• Electrolyte contains water (H2O) and sulfuric acid (H2SO4).
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• Current flows in the cell from the negative to the positive plates.
• Electrolyte separates into hydrogen (H2) and sulphate (SO4).
• The free sulphate combines with the lead (both lead oxide and sponge
lead) and becomes lead sulphate (PbSO4).
• The free hydrogen and oxygen combine to form more water, diluting
the electrolyte.
Fully Discharged
• Both plates are fully sulphated.
• Electrolyte is diluted to mostly water.
Figure 12-4: The chargingdischarging cycle has four
distinct stages, all based on a
reversible chemical reaction
with lead and sulfuric acid. Here
is ‘fully charged’ and
‘discharging’ shown.
• Reverses the chemical reaction that took place during discharging.
• Sulphate (SO4) leaves the positive and negative plates and combines
with hydrogen (H2) to become sulfuric acid (H2SO4).
• Hydrogen bubbles form at the negative plates; oxygen appears at the
positive plates.
• Free oxygen (O2) combines with lead (Pb)
at the positive plate to become lead oxide (PbO2).
Figure 12-5: These two stages illustrate
‘discharged’ and ‘charging’
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Capacity Ratings An automotive battery must be able to crank the
engine for starting and still have enough reserve capacity to operate the
vehicle systems once the engine starts.
Battery capacity is:
The amount of electrical energy the battery can deliver when fully
Cold-Cranking Amperes
-are determined by the size and total number of plates and the volume
and strength of the electrolyte.
While it is operating the starter, the battery experiences a large discharge
The measure of a battery‘s ability to provide this current is expressed as
Cold-Cranking Amperes, or CCA Rating. The CCA Rating specifies (in
amperes) the discharge current a fully charged battery can deliver -at
−18ºC, -for 30 seconds, -while maintaining at least 1.2 volts per cell
(or 7.2 volts total for a six-cell, 12 volt battery).
Ampere-hours (Ah) The Ampere-hours, or Ah rating, is another
important measure of a battery‘s design performance. The Ah rating
expresses the discharge current a fully charged battery can deliver for 20
hours at 27˚C, -while maintaining a voltage of at least 1.75 volts per
cell (total of 10.5 volts for a 6 cell, 12 volt battery).
EXAMPLE A battery that can deliver 4 amps for 20 hours is rated at 80
Batteries in passenger cars typically have an Ah rating between 40 and
80 amp-hours, depending on vehicle model. Diesel engines generally
need larger capacity batteries.
Figure 12-6: A visual inspection can reveal
easy-to-correct problems with the battery
and conditions that will require battery
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Visual Inspection
Battery service should always
begin with a thorough visual
inspection. Such an inspection
may reveal simple, easily
problems that require battery
replacement without further
Include these steps in a visual
Figure 12-7: The battery indicator eye can give a quick indication
1. Check for cracks in the of the battery condition.
particularly around battery terminals. These are sometimes overstressed
when removing and installing battery cables. Replace the battery if there
is any evidence of cracking.
2. Check for cracked or broken cables or connections. Replace cables or
connectors as necessary.
3. Check for corrosion on terminals and dirt or acid on the case top. Clean
the terminals and case top with a mixture of water and baking soda. Wire
brush heavy corrosion on the terminals.
4. Check for a loose battery hold-down and loose cable connections.
Tighten as needed.
5. On batteries with removable vent caps, remove the caps and check the
electrolyte level. Add distilled water to each cell to restore the level if
necessary. Avoid overfilling and never add additional acid. Tap water
adds contaminants, and will reduce battery efficiency.
6. Check the indicator eye. A red eye indicates the battery is severely
discharged or the electrolyte is low. The electrolyte level is sufficient and
the battery is at least 25% charged if at least some blue is showing.
7. Check for cloudy or discoloured electrolyte. This can be caused by
overcharging or excessive vibration. Correct the problem and replace the
Safety First Safety should be your first consideration whenever you
inspect, test, or replace a lead acid battery. The electrolyte contains
sulfuric acid. This acid can burn your skin, injure your eyes, and damage
the vehicle, your tools, or your clothing.
If you splash electrolyte onto your skin or into your eyes, immediately
rinse it away with large amounts of clean water. Contact a doctor
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If you spill electrolyte onto any part of the vehicle, neutralize the acid with
a solution of baking soda and water, then rinse liberally to remove any
When a battery is charging, the electrolyte may release gasses (hydrogen
and oxygen). Hydrogen gas is explosive, and oxygen supports
combustion. A flame or spark near a charging battery can cause an
Take the following precautions when working with automotive batteries:
• Wear gloves and safety glasses.
• Never use spark-producing tools near the battery.
• Never lay any tools on the battery.
• If it is necessary to remove the battery cables, always remove the
ground first.
• When connecting battery cables, always connect the ground cable last.
• Do not use the battery ground terminal when checking for ignition spark.
• Take care not to spill electrolyte into your eyes, onto your skin, and onto
any part of the vehicle.
• If you mix electrolyte, pour the acid into the water (not the water into the
• Always follow the recommended procedures for battery testing,
charging, and for connecting jumper cables between two batteries.
Battery Drain Tests
There are two tests for battery drain: Parasitic load and Surface
A parasitic load is created by a device that draws current even when the
ignition switch is turned to ‖Off". Even a small current can discharge the
battery, if the vehicle is not used for an extended time.
Check for a parasitic load as follows:
1.Connect an ammeter in series between the battery negative terminal
and the ground cable connector.
2.Select the appropriate scale and read the current draw.
3.Modern vehicles typically draw between 20 and 75 milliamps (this is
current used to maintain electronic memories).
4.Any reading higher than 100 milliamps is unacceptable. Locate and
correct the cause of the excess parasitic drain.
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Make sure that you wait a few minutes before checking for parasitic
load. After the vehicle is shut down or a door is opened, parasitic load
may be 50−75 milliamps, depending on model, for a few minutes.
Figure 12-8: Parasitic load current and
battery surface discharge can cause
batteries to discharge over time
Surface discharge is a small current that runs between the two battery
terminals, across the surface of the battery. This can occur only when that
surface is dirty.
Check for surface discharge as follows:
1. Connect a voltmeter, black test lead (negative) to the battery‘s negative
terminal; red test lead (positive) to the top of the battery case.
2. Select an appropriate scale and read the voltage.
3. If the meter reading is higher than 0.5 volts clean the case top with a
solution, of baking soda and water.
Fast Charging Fast charging is used to charge the battery for a short
period of time with a high rate of current. Fast charging may shorten
battery life. If time allows, slow charging is preferred. Some low
maintenance batteries cannot be fast charged.
Slow Charging High charging rates are not good for completely
charging a battery. To completely charge a battery, slow charging with a
low current is required.
Slow charging procedures are the same as those for fast charging, except
for the following:
1. The maximum charging current should be less than 1/10th of the
battery capacity. For instance, a 40 Ah battery should be slow
charged at 4 amps or less.
2. Set the charger switch to the slow position (if provided).
3. Readjust the current control switch, if needed, while charging.
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4. As the battery gets near full charge, hydrogen gas is emitted. When
there is no further rise in battery voltage for more than one hour, the
battery is completely charged.
Battery Voltage will be 12.6 volts or higher.
Jump Starting Jump starting requires proper battery connecting
procedures to prevent sparks. Jump start a vehicle using the following
1. Connect the two positive cables using the positive jumper leads.
2. Connect one end of the negative jumper lead to the booster battery.
3. Connect the other lead of the negative jumper lead to a good ground
on the vehicle with the dead battery. This location could be:
• The vehicle frame.
• The engine block.
Using this method ensures that any possible sparks occur away from the
Figure 12-9:
Jump start as follows:
1. Positive to positive,
2. Negative to good battery,
3. Negative to good ground of vehicle with dead battery.
NOTE: Battery jumper leads should be high quality and have a large wire
gauge (such as 4 gauge) to safely carry the current necessary to jump
start a vehicle.
CAUTION: Never try to jump start a vehicle with a visibly damaged
battery or if no battery is present. Vehicle damage and risk of battery
explosion are possible.
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Chapter 13: Fundamentals of Electromagnetism
Back to ToC
In 1820, scientists discovered that current-carrying conductors are
surrounded by a magnetic field. A conductor, such as a copper wire, that
is carrying an electrical current creates a magnetic field around the
conductor and is called electromagnetism.
Figure 13-1: Electromagnetism
This magnetic field can be observed by the use of a compass, as shown
in Figure 13-1. The polarity of the magnetic field changes depending on
the direction in which the magnetic field is created.
Straight Conductor
The magnetic field surrounding a straight, current-carrying conductor
consists of several concentric cylinders of flux the length of the wire, as in
Figure 13-2. The strength of the current determines how many flux lines
(cylinders) there will be and how far out they extend from the surface of
the wire.
Electromagnetic Field Rules
Figure 13-2: A magnetic field
surrounds a straight currentcarrying conductor.
Figure 13-3: Left-hand rule for field direction; used with
the electron-flow theory.
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The following rules apply with electromagnetic fields:
 The magnetic field moves only when the current through the conductor
is changing— either increasing or decreasing.
 The strength of the magnetic field is directly proportional to the current
flow through the conductor. The greater the current flow, the stronger
the magnetic field. If the current flow is reduced, the magnetic field
becomes weaker.
Left-Hand Rule
Magnetic flux cylinders have direction, just as the flux lines surrounding a
bar magnet have direction. The left-hand rule is a simple way to
determine this direction. When you grasp a conductor with your left hand
so that your thumb points in the direction of electron flow (- to +) through
the conductor, your fingers curl around the wire in the direction of the
magnetic flux lines, as shown in Figure 13-3.
Right-Hand Rule It is important to note at this point that in automotive
electricity and magnetism, we use the conventional theory of current (+
to -), so you use the right-hand rule to determine the direction of the
magnetic flux lines, as shown in Figure 13-4. The right-hand rule is used
to denote the direction of the magnetic lines of force, as follows: The right
hand should enclose the wire, with the thumb pointing in the direction of
conventional current flow (positive to negative), and the finger tips will
then point in the direction of the magnetic lines of force, as shown in
Figure 13-4.
For the rest of this chapter, the electron-flow theory (negative to
positive) and the left-hand rule are used.
Figure 13-4: Right-hand rule for field direction; used
with the conventional flow theory.
Figure 13-5: Current
direction symbols
Field Interaction
The cylinders of flux surrounding current-carrying conductors interact with
other magnetic fields. In the following illustrations, the cross symbol (+)
indicates current moving inward, or away from you. It represents the tail
Reproduced by Speciss College with permission from Kevin Sullivan -
of an arrow. The dot symbol (.) represents an arrowhead and indicates
current moving outward, or toward you (Figure 13-5). If two conductors
carry current in opposite directions, their magnetic fields are also in
opposite directions (according to the left-hand rule). If they are placed
side by side, Figure 13-6, the opposing flux lines between the conductors.
Current-carrying conductors tend to move out of a strong field into a weak
field, so the conductors move away from each other (Figure 13-6). If the
two conductors carry current in the same direction, their fields are in the
same direction.
In Figure 13-7, the conductors are drawn into this weak field; that is, they
move closer together.
Figure 13-6: Conductors with
opposing magnetic fields.
Figure 13-7: Conductors with the
same magnetic fields.
Motor Principle
Electric motors, such as automobile starter motors, use field interaction to
change electrical energy into mechanical energy (Figure 13-8). If two
conductors carrying current in opposite directions are placed between
strong north and south poles, the magnetic field of the conductor interacts
with the magnetic fields of the poles. The counter clockwise field of the
top conductor adds to the fields of the poles and creates a strong field
beneath the conductor. The conductor tries to move up to get out of this
strong field. The clockwise field of the lower conductor adds to the field of
the poles and creates a strong field above the conductor. The conductor
tries to move down to get out of this strong field. These forces cause the
centre of the motor or armature where the conductors are mounted to turn
in a clockwise direction. This process is known as magnetic repulsion.
Figure 13-8: Electric motors use
field interaction to produce
mechanical energy and
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Loop Conductor
Bending the wire into a loop can strengthen the field around a straight
conductor. As the wire is bent, the fields, which meet in the centre of the
loop, combine their strengths (Figure 13-9). The left-hand rule also
applies to loop conductors.
Coil Conductor
If several loops of wire are made into a coil, the magnetic flux density is
further strengthened. Flux lines around a coil are the same as the flux
lines around a bar magnet (Figure 13-10). They exit from the north pole
and enter at the south pole. Use the left-hand rule to determine the north
pole of a coil. If you grasp a coil with your left hand so that your fingers
point in the direction of electron flow, your thumb points toward the north
pole of the coil. Increasing the number of turns in the wire, or increasing
the current through the coil, or both, can strengthen the magnetic field of
a coil.
Figure 13-10: Coil Conductor
Figure 13-9: Loop Conductor
Figure 13-11: Coil with Iron Core
There is a third way to strengthen the magnetic field surrounding a
current-carrying conductor. Because soft iron is very permeable,
magnetic flux lines pass through it easily. If a piece of soft iron is placed
inside a coiled conductor, the flux lines concentrate in the iron core, as
shown in Figure 13-11, rather than pass through the air, which is less
permeable. This concentration of force greatly increases the strength of
the magnetic field inside the coil. A coil with an iron core is called an
electromagnet. Electromagnetic field force is often described as
Magneto-Motive Force (MMF). The strength of the Magneto-Motive Force
is determined by:
• The higher the current flow through the coil, the stronger the MMF.
• The higher the number-of-turns of wire in the coil, the stronger the
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One common automotive use of electromagnets is in a device called a
relay. A relay is a control device that allows a small amount of current to
trigger a large amount of current in another circuit. A simple relay (Figure
13-12) contains an electromagnetic coil in series with a battery and a
switch. Near the electromagnet is a movable flat blade, or armature, of
some material that is attracted by a magnetic field. The armature pivots at
one end and is held a small distance away from the electromagnet by a
spring. A contact point made of a good conductor is attached to the free
end of the armature. Another contact point is fixed a small distance away.
Relays may also be designed with normally closed contacts that open when
current passes through the electromagnet.
Most relays contain a device that protects circuitry from the voltage spike that
occurs when the coil is de-energized. In older vehicles, the protective device is
usually a diode (as in the Figure 13-13). A diode is a semiconductor device that
can be useful in several ways. In a relay, the diode is located in parallel with the
coil, where it dissipates the voltage spike.
Today many automobile relays include a resistor, rather than a diode, to protect
the control circuit (as in the Figure 13-14). The resistor dissipates the voltage
spike in the same way that a diode does.
Figure 13-12: Automotive relay
(cover removed)
Figure 13-14: Relay with
protection resistor
Figure 13-13: Protection diode
Electromagnetic Induction
Along with creating a magnetic field with current, it is also possible to
create current with a magnetic field.
Magnetic flux lines create an electromotive force, or voltage, in a
conductor if either the flux lines or the conductor is moving (relative
motion). This process is called electromagnetic induction, and the
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resulting electromotive force is called induced voltage (Figure 13-15). If
the conductor is in a complete circuit, current exists. It happens when the
flux lines of a magnetic field cut across a wire (or any conductor). It does
not matter whether the magnetic field moves or the wire moves. When
there is relative motion between the wire and the magnetic field, a voltage
is produced in the conductor. The induced voltage causes a current to
flow; when the motion stops, the current stops.
Voltage is induced when magnetic flux lines are broken by a conductor
(Figure 13-15).
This relative motion can be a conductor moving across a magnetic
field (as in a DC generator), or a magnetic field moving across a
stationary conductor (as in AC generators and ignition coils).
In both cases, the induced voltage is caused by relative motion between
the conductor and the magnetic flux lines.
Figure 13-15: Voltage can be induced by the relative motion
between a conductor and a magnetic field.
Chapter 14: Starting System
Back to ToC
The starting system:
• Uses a powerful electric motor to drive the engine at about 200 RPM
(fast enough to allow the fuel and ignition systems to operate).
• Drives the engine through a pinion gear engaged with a ring gear on
the flywheel.
• Disengages as soon as the engine starts.
Starting System Components
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Figure 14-1: Location of starter motor
These components make up a typical starting system:
• Starter motor
• Magnetic switch
• Over-running clutch
• Ignition switch contacts
• Park/neutral position (A/T) or clutch start (M/T) switch
• Clutch start cancel switch (on some models)
• Starter relay
Starter Motor
Modern vehicles are fitted with one of two types of starter motors:
• Gear reduction
• Planetary Reduction Segment (PS)
Gear-Reduction Starter Motor
The gear-reduction starter motor contains the components shown. This
type of starter has a compact, high-speed motor and a set of reduction
While the motor is smaller and weighs less than conventional starting
motors, it operates at higher speed. The reduction gears transfer this
torque to the pinion gear at 1/4 to 1/3 the motor speed. The pinion gear
still rotates faster than the gear on a conventional starter and with much
greater torque (cranking power).
Reproduced by Speciss College with permission from Kevin Sullivan -
Figure 14-2: Gear Reduction Starter Motor
The reduction gear is mounted on the same shaft as the pinion gear.
Unlike the conventional starter, the magnetic switch plunger acts directly
on the pinion gear (not through a drive lever) to push the gear into mesh
with the ring gear.
This type of starter is now used on most modern vehicles. Ratings range
from 0.8 kW on most passenger cars, including diesel models. The coldweather package calls for a 1.4 kW or 1.6 kW starter, while a 1.0 kW
starter is common on larger models.
The gear-reduction starter is the replacement starter for most
conventional starters.
Older vehicles use conventional type starters.
This type of starter drives the pinion gear directly. The
pinion gear turns at the same speed as the motor
shaft. These starters are heavier and draw more
current than gear reduction and PS type starters.
Over-running Clutch
Both conventional and gear reduction starter motors are fitted with a oneway, over-running clutch. The clutch prevents damage to the starter when
the engine starts.
Reproduced by Speciss College with permission from Kevin Sullivan -
Figure 14-3: Conventional type starter motors drive the pinion
Clutch Operation:
1. During engine start, the starter pinion gear drives the engine‘s flywheel
ring gear.
2. Once the engine fires, the ring gear almost instantly begins to turn
faster than the starter pinion gear. Over speeding would damage the
starter motor if it were not immediately disengaged from the pinion
3. The clutch uses its wedged rollers and springs to disengage the pinion
shaft from the clutch housing (which turns with the motor armature). This
happens any time the pinion shaft tries to turn faster than the clutch
Figure 14-4: The clutch housing, armature, and pinion gear turn together.
Reproduced by Speciss College with permission from Kevin Sullivan -
Ignition Switch
The ignition switch incorporates contacts to provide B+ to the starter. The
relay energizes the starter magnetic switch when the driver turns the
ignition key to the START position.
The park/neutral position switch prevents operation of the starter motor
unless the shift lever is in Park or Neutral. The switch contacts are in
series with the starter control circuit. (Figure 14-5)
Clutch Start Switch Sometimes for manual transmissions a clutch start
switch performs the same function as the park/neutral position switch.
The clutch start switch opens the starter control circuit unless the clutch is
engaged. (Figure 14-6)
Figure 14-5: With key to START
position, B+ is applied to the starter
Figure 14-6: Clutch Start
Switch acts like Park/Neutral
Gear-Reduction Starter Operation
Ignition switch in ST:
1. Current travels from the battery through terminal ―50" to the hold-in and
pull-in coils. Then, from the pull-in coil, current continues through terminal
―C" to the field coils and armature coils.
2. Voltage drop across the pull-in coil limits the current to the motor,
keeping its speed low.
3. The magnetic switch plunger pushes the pinion gear to mesh with the
ring gear.
4. The screw spline and low motor speed help the gears mesh smoothly.
Reproduced by Speciss College with permission from Kevin Sullivan -
Figure 14-7: The plunger pulls the drive lever, which moves the pinion
gear into engagement with the ring gear.
Pinion and ring gears engaged:
1. When the gears are meshed, the contact plate on the plunger turns on
the main switch by closing the connection between terminals ―30" and
2. More current goes to the motor and it rotates with greater torque.
3. Current no longer flows in the pull-in coil. The plunger is held in
position by the hold-in coil‘s magnetic force.
Ignition switch in ON:
1. Current no longer present at terminal ―50," but the main switch remains
closed to allow current from terminal ―C" through the pull-in coil to the
hold-in coil.
2. The magnetic fields in the two coils cancel each other, and the plunger
is pulled back by the return spring.
3. The high current to the motor is cut off and the pinion gear disengages
from the ring gear.
4. The armature has less inertia than the one in a conventional starter.
Friction stops it, so a brake is not needed.
Figure 14-8: current flow in the 2 phases
Reproduced by Speciss College with permission from Kevin Sullivan -
PS Starter Motors
Most late models are fitted with Planetary Reduction-Segment Conductor
(PS) starters.
Planetary reduction allows the starter motor to operate at a higher
speed than a conventional starter.
• The reduction gear set reduces the pinion gear speed compared to
motor shaft speed.
• Higher motor speed yields greater torque.
Segment conductor type starters incorporate several design
• More compact
• Lighter weight
• Greater output torque
Figure 14-9: PS Starter - Overview
PS Starter Motors Construction
Armature coil wires − the coil wires in a PS starter armature are square in
 More compact winding than round cross-section wires
 Greater output torque
 Surface commutator − the square shape of the armature conductors
allow the surface of the armature to act as a commutator.
 Field coils − Conventional starters use field coils. PS type starters use
two types of permanent magnets instead:
 Main magnets
Reproduced by Speciss College with permission from Kevin Sullivan -
 Inter-polar magnets
The two types of magnets are arranged alternately inside the yoke.
• Work together to increase magnetic flux
• Allows shorter yoke
Figure 14-10: PS Starter – Construction: Coil wires in PS type starters are square
in cross-section for more compact winding and greater output torque.
Diagnosis and Testing
The starting system requires little maintenance. The battery should be
fully charged and connections kept clean and tight. Diagnosis of starting
system problems is usually straightforward. Problems may be electrical or
mechanical. The Starting System Troubleshooting chart lists the most
common starting system problems, the possible causes, and
recommended actions to resolve the problem. Begin with a thorough
visual inspection. If this fails to turn up the possible cause, several tests
are available to help you find the problem:
• Starter motor current draw test
• Voltage drop tests
• Operational and continuity tests
• Starter motor bench tests
Reproduced by Speciss College with permission from Kevin Sullivan -
Visual Inspection
A visual inspection of the starting system can save you time and effort by
uncovering obvious or simple and easy-to-fix problems.
The battery contains sulfuric acid. Take precautions to avoid possible
injury or damage.
• Remove rings, wristwatch, and any other jewellery that might contact
the battery terminals before beginning the inspection.
• Wear safety glasses and protective clothing to protect you from acid.
Include these components in your inspection:
• Battery
• Starter
• Ignition switch
• Park/neutral position or clutch start switch
Inspect visually
• Inspect the battery for external damage to the case or the cables,
corroded terminals, and loose connections.
• Check the battery‘s state of charge (with a battery analyser). Charge if
• Check the electrolyte level and top up with distilled water if needed.
• Inspect the starter motor for external damage to the case or wiring
(including the magnetic switch circuit), corroded terminals, and loose
• Check for loose mounting hardware. Tighten as needed.
• Inspect the ignition switch for loose connections and damaged wiring.
• Confirm that the battery voltage is available at the magnetic switch with
the ignition switch set to ON and the clutch switch or neutral start switch
• If you suspect the ignition switch is faulty, use a remote starter switch
and jumper wire to confirm starter operation.
• Conduct a voltage drop test to verify proper operation (max. 0.1 V drop).
Reproduced by Speciss College with permission from Kevin Sullivan -
Current Draw Test
The starter current draw test effectively checks the entire starting system.
A special purpose tester connects to the battery to measure starting
current and cranking voltage.
The procedure shown here applies to the VAT−40 and (with some minor
differences) the VAT−60:
Figure 14-11: How to connect the Volt Ampere Tester
1. Make a visual inspection of the battery, electrolyte, and battery cables.
2. Turn off all electrical accessories and lights in the vehicle; set ignition
switch to OFF.
3. Disable the fuel or ignition system so the engine will not start.
4. Connect the tester in this sequence:
• Red lead to positive battery terminal
• Black lead to negative battery terminal
• Current probe on negative battery cable
5. For VAT−40, set the voltage selector to EXT 18 (volts).
6. Without cranking the engine, note the voltage reading.
• Should be at least 12.6 volts.
• Recharge the battery before proceeding if the voltage is below 12.6
7. Crank the engine and observe the voltage and current readings.
• Engine speed should be between 200 and 250 RPM while cranking.
• Voltage should be at or above the service specification (refer to
appropriate repair manual).
• Current should be at or below the service specification (refer to
appropriate repair manual).
8. When finished with the test, disconnect the tester leads and enable the
fuel or ignition system (replace fuse or relay).
For most modern vehicles, you can pull the Electronic Fuel Injection (EFI)
fuse or relay to prevent engine start.
Reproduced by Speciss College with permission from Kevin Sullivan -
You can connect the current probe to either battery cable. Just be sure to
orient the arrow on the probe correctly. The arrow should point down
(away from the battery) for the positive cable; the arrow should point up
(toward the battery) for the negative cable.
Do not crank the engine longer than 10 seconds at a time.
Voltage Drop Tests - Starter Motor Circuit
Voltage drop tests can find excessive resistance Do not crank the engine longer
in the starting system.
than 10 seconds at a time.
High resistance in the starter motor circuit can:
• Reduce starter motor current.
• Cause slow cranking.
Preparation − Prepare the tester and the vehicle with these steps:
1. Disable the fuel or ignition system so engine will not start while
NOTE: For most modern vehicles, you can pull the Electronic Fuel
Injection (EFI) fuse or relay to prevent engine start.
2. Set the Voltmeter selector of the DMM, select a low voltage scale.
3. Connect the DMM leads to measure voltage drop for the following:
• Battery + post to + cable
• Battery + cable to starter
• Starter relay to starter (PS type)
• Starter case to − cable • − cable to − battery post
• Terminal C to terminal 30 (gear reduction type)
• Battery to terminal 50 (gear reduction type)
Normal voltage drops in the starting system are in the range of 0.2
volts to 0.5 volts.
Battery Positive Cable
This test measures the voltage drop
across the positive battery post to the
cable and the connections at the battery
and the starter.
Figure 14-12: Meter connected to measure
positive voltage drop.
Reproduced by Speciss College with permission from Kevin Sullivan -
Crank the engine and note the voltage reading:
• 0.5 volts or less is acceptable resistance
• More than 0.5 volts is excessive resistance
If you find excessive resistance, perform these steps:
• Isolate the cause
• Repair the fault
• Re-test the voltage drop
Excessive resistance could be caused by any of these:
• Damaged battery cable
• Poor connection at battery or starter terminal
• Defective magnetic switch
Battery Negative Cable
This test measures the voltage drop across the negative battery cable,
the connections at the battery and the starter, and the connection to
ground through the starter motor case:
Figure 14-13: Meter connected to measure negative voltage
1. Connect the tester or meter leads:
• Red lead to the starter motor housing
• Black lead to negative terminal of the battery
2. Crank the engine and note the voltage reading:
• 0.2 volts or less is acceptable resistance
• More than 0.2 volts is excessive resistance
If you find excessive resistance, perform these steps:
• Isolate the cause and repair the fault
• Re-test the voltage drop
Excessive resistance could be caused by any of these:
• Damaged battery cable
• Poor connection at battery or starter terminal
• Poor connection between the starter case and the vehicle chassis.
Reproduced by Speciss College with permission from Kevin Sullivan -
Magnetic Switch
This test measures the voltage drop across the magnetic switch:
Figure 14-14: Meter connected to measure voltage drop at
the magnetic switch (solenoid).
NOTE: Starters with planetary gear reduction
do not have a magnetic switch.
1. Connect the tester or meter leads:
• Red lead to starter terminal C
• Black lead to starter terminal 30
2. Crank the engine and note the voltage reading:
• 0.3 volts or less is acceptable resistance
• More than 0.3 volts is excessive resistance
If you find excessive resistance, perform these steps:
• Isolate the cause and repair the fault
• Re-test the voltage drop
A faulty magnetic switch could cause excessive resistance.
Figure 14-15: Starter Control Circuit: Voltage drop testing can find excessive resistance.
Reproduced by Speciss College with permission from Kevin Sullivan -
Voltage Drop Tests - Starter Control Circuit
Excessive resistance in the starter control circuit can reduce the voltage
available to the magnetic switch.
Symptoms of excessive voltage include the following:
• Pinion gear does not engage
• Pinion gear engages only partially
There are several areas where excessive resistance can occur:
• ST contacts of the ignition switch
• Neutral start switch /clutch start switch
• Circuit wiring and connections
Measure the voltage drop across the ignition switch and the neutral
start/clutch start switch:
• 0.1 volts or less is acceptable
• More than 0.1 volts is an indication of excessive resistance
Ignition Switch and Key
Check the ignition switch both mechanically and electrically.
Mechanically − Switch should turn smoothly without binding. Binding
may mean problems with the lock cylinder or the electrical contacts.
Check the ignition key for excessive wear or rough surfaces.
Electrically − Disconnect the battery ground cable and check for
continuity through the ST contacts. Refer to the appropriate service
manual for wiring details.
Reproduced by Speciss College with permission from Kevin Sullivan -
_ ______ _
_ ___________ _
______ _
______ _
___________ _
__________ _
_ ______ _
_ ___________ _
Figure 14-16: Troubleshooting Chart
Reproduced by Speciss College with permission from Kevin Sullivan -
Chapter 15: Charging System
Back to ToC
Function of the Charging System
The charging system has two essential functions:
• Generate electrical power to run the vehicle‘s electrical systems
• Generate current to recharge the vehicle‘s battery
Electrical power − At low engine speeds, the battery may supply some
of the power the vehicle needs. At high engine speeds, the charging
system handles all of the vehicle‘s electrical requirements.
Charging − Alternator (generator) output is higher than battery voltage to
recharge the battery.
Figure 15-1: This figure shows the major components of the charging
Charging System Components
These components make up the charging system:
• Alternator
• Voltage regulator
• Battery
• Charging indicator
The alternator contains these main components:
 Stator (attached to alternator housing, remains stationary)
 Rotor (spins inside the stator)
 Rectifier
 Voltage regulator
Slip rings and brushes make an electrical connection to the spinning
Reproduced by Speciss College with permission from Kevin Sullivan -
Figure 15-2: Exploded view of the alternator’s main components.
The alternator generates electricity (AC becomes DC) through these
 Engine power drives the alternator rotor through a pulley and drive belt.
 The alternator rotor spins inside the windings of the stator.
 The stator windings generate an alternating current.
 Rectifier diodes change the alternating current (AC) into direct current
Voltage Regulator
The voltage regulator controls the alternator‘s output current to prevent
over-charging and under-charging of the battery. It does this by regulating
the current flowing from the battery to the rotor‘s field coil.
Today‘s IC voltage regulator is a fully electronic device, using resistors
and diodes.
Figure 15-3: Modern IC voltage regulator
Reproduced by Speciss College with permission from Kevin Sullivan -
The battery supplies current to energize the alternator field coil. The
battery also acts as a voltage stabilizer. The battery must always remain
attached to the electrical system while the engine is running.
Charging Indicator
The charging indicator is usually an ON/OFF warning lamp.
When the system is running, the light should be OFF. The lamp Figure 15-4:
lights when the charging system is not providing sufficient symbol for
Current in the charging system changes for these three
different operating conditions:
• Ignition switch to ON − engine stopped
• Ignition switch to ON − engine running alternator output below
desired voltage
• Ignition switch to ON − engine running alternator output above
desired voltage
Ignition switch to ON − engine stopped:
• As soon as the ignition switch is turned to ON, the IC regulator causes
a current of about 0.2 amps through the rotor‘s field coil.
• The IC regulator turns on the charging indicator.
• There is no output from the stator because the rotor is not turning.
Ignition switch to ON − engine running, alternator output below
desired voltage:
• The windings in the stator generate a voltage any time the rotor is
energized and spinning.
• Voltage generated in the stator is applied to the voltage regulator.
• If the alternator output voltage is below 14.5 volts, the voltage
regulator responds by increasing current through the field coil of the
rotor. This causes the voltage to increase.
• A charging current is sent to the battery.
Ignition switch to ON − engine running alternator output above
desired voltage:
When the voltage regulator senses alternator output at or above 14.5
• It reduces current through the rotor field coil.
• This reduces alternator output voltage.
• No charging current goes to the battery.
• Terminal ‗S‘ is an input to the regulator to monitor voltage levels.
• Terminal ‗B‘ is alternator output.
Reproduced by Speciss College with permission from Kevin Sullivan -
Terminal S disconnected:
• The voltage regulator does not detect voltage.
• The voltage regulator regulates voltage at Terminal B to 16 volts and
lights the Charging Indicator.
Terminal B disconnected:
• No charging voltage available for battery.
• This condition could result in voltage regulator damage.
Figure 15-5: Complete wiring of charging system
Reproduced by Speciss College with permission from Kevin Sullivan -
Diagnosis and Testing
The charging system requires little maintenance. The battery should be
fully charged and connections kept clean and tight.
Diagnosis of charging system problems is typically straightforward.
Problems may be electrical or mechanical. The troubleshooting flow
diagram on the next page lists the most common charging system
problems, the possible cause, and recommended actions to resolve the
Begin with a thorough visual inspection. If this fails to turn up the possible
cause, several tests are available to help you find the problem:
• Alternator output test (no load)
• Alternator output test (with load)
• Voltage drop tests
• Charging current relay test
• Diode tests
Reproduced by Speciss College with permission from Kevin Sullivan -
Troubleshooting Flow Diagram
Use this flow diagram to troubleshoot charging systems with compact, high speed
Figure 15-7: Troubleshooting Chart
Charging System Visual Inspection
Include the following items in a visual inspection of the charging system:
1. Battery
2. Fusing
3. Alternator Drive Belt
4. Alternator Wiring
5. Noise
6. Charging Indicator
Reproduced by Speciss College with permission from Kevin Sullivan -
Figure 15-18: Check specific
Figure 15-19: Fusible links must be
part of the visual inspection of the
charging system.
Item 1: Battery
Visual Inspection –see Chapter 12 Battery
Other Battery Checks
State of Charge − Check the specific gravity of the electrolyte to
determine the battery‘s state of charge.
 Specific gravity should be between 1.25 and 1.27 (at 26.7°C).
 Condition − Check overall battery condition with a battery analyser.
Item 2: Fusing
• Refer to the EWD to identify fuses and fusible links in the charging
system for the vehicle under test. Check these components for
Item 3: Alternator Drive Belt
• Good condition
• Correct alignment
• Proper tension
Item 4: Alternator Wiring
 Make sure all connections are clean and tight.
 Check wiring for frayed insulation and other physical damage.
Item 5: Alternator Noise
Listen for any unusual noise while the alternator is operating:
 Squealing may indicate a bearing problem or a worn or improperly
tensioned and adjusted drive belt.
 Hissing may be a sign that one or more of the diodes are defective,
because of a pulsating magnetic field and vibration.
Reproduced by Speciss College with permission from Kevin Sullivan -
Item 6: Charging Indicator
• Indicator lights with ignition ON and engine not running.
• Indicator goes off with engine running.
If the indicator does not
operate as described
above, refer to the
appropriate Electrical
Wiring Diagram and check
the indicator circuit.
Figure 15-20: Alternator drive belts must be in good condition and be
properly aligned and tensioned.
Figure 15-21: Inspect
wires and connections
at the alternator.
Alternator Output Test (No Load)
Use the following steps to perform the test with a Sun VAT−40 or VAT−60
1. Set the tester‘s Load control to OFF.
2. Connect the tester leads.
 Red lead to positive terminal.
 Black lead to negative terminal.
 Clamp the ammeter clamp-on probe onto the battery‘s ground cable.
3. Set the tester‘s voltage range to the appropriate setting.
4. Zero both meters on the tester, if needed.
5. Turn the ignition switch to ON (do not start the engine).
6. Record the ammeter reading.
 This is the discharge current (typically about 6 amps).
 Alternator must supply this amount of current before it can provide
charging current to the battery.
7. Start the engine and adjust engine speed to about 2,000 RPM.
8. Allow engine to warm up for 3 to 4 minutes.
9. Record the ammeter reading.
 Add the discharge current (from Step 4) to the reading now on the
ammeter. The total should be less than 10 amps.
Reproduced by Speciss College with permission from Kevin Sullivan -
 The battery may not have been fully charged if the total current is more
than 10 amps. Monitor the ammeter; the reading should decrease as
the battery charges.
10. Record the voltmeter reading.
 The voltmeter reading should be within specification for the alternator
during the entire test. This value is typically between 13 and 15 volts;
refer to the appropriate service manual for the correct specification.
 If the voltmeter reading is higher than specified, the voltage regulator is
probably defective. Replace the regulator if possible or replace the
 If the voltmeter reading is lower than specified, the cause could be a
bad regulator or a fault in the alternator windings. Replace the
alternator if it has an internal voltage regulator.
 For alternators with externally mounted regulators, confirm the cause
by grounding Terminal F on the alternator. This bypasses the regulator.
If voltage increases, the voltage regulator is probably defective. If the
voltage remains low, replace the alternator; there is a problem with the
11. Remove ground from alternator Terminal F.
Figure 15-22: Hook-up of combined Volt Ampere Tester (e.g. SUN VAT40)
Reproduced by Speciss College with permission from Kevin Sullivan -
Alternator Output Test (With Load)
Use the following steps to perform the test with a Sun VAT−40 or VAT−60
1. Keep the tester connections as for the alternator output test with no
2. Adjust engine speed to specified RPM (refer to the appropriate
service manual).
3. Adjust the tester‘s load control to obtain the highest ammeter reading
possible while keeping the voltage reading at or above 12 volts.
4. Record the highest ammeter reading.
 The reading should be within 10% of the alternator‘s rated output.
 Replace the alternator if the reading is more than 10% below the
value specified.
Figure 15-23: Alternator Output Test (With Load) This
figure shows the location of the “F” terminal for various
alternator types.
Voltage Drop Test
Voltage drop tests can isolate unwanted high resistance in the charging
system. High resistance can cause these symptoms:
 Charging system cannot fully charge battery.
 Abnormally high current is drawn from battery under high load
Reproduced by Speciss College with permission from Kevin Sullivan -
Figure 15-24: Voltage drop tests can isolate high resistance in the
charging system. Test voltage drop on the positive and the ground
side of the battery.
Use a DMM to perform a voltage drop test on the positive side of the
battery as follows:
1. Connect the red meter lead to Terminal B on the alternator.
2. Connect the black meter lead to the positive battery terminal.
3. Start the engine; adjust engine speed to 2,000 RPM.
4. Note the voltage reading.
• The voltage drop should be less than 0.2 volts.
• If the reading is higher, look for poor connections at the alternator and
at the battery. Also, look for damaged wires or corroded wires.
Test for voltage drop on the ground side of the battery as follows:
5. Keep the engine running at 2.000 RPM.
6. Connect the red meter lead to the negative (ground) battery terminal.
7. Connect the black meter lead to the alternator frame.
8. Note the voltage reading.
Reproduced by Speciss College with permission from Kevin Sullivan -
 The voltage drop should be less than 0.2 volts.
 If the reading is higher, look for poor connections between the battery
and ground and from the alternator frame to ground.
Also, look for a damaged or corroded battery ground cable.
Chapter 16: Conventional Ignition System
Basic ignition
Back to ToC
Figure 16-1: Conventional Ignition System
The ignition system ignites the fuel in the gasoline engine. There are
three general types of ignition system: breaker ignition; electronic ignition;
and direct ignition.
A basic ignition system consists of:
 the battery
 low-tension cables
 the ignition coil
 distributor
 coil high-tension cable
 spark plug cables
 and spark plugs
The ignition system provides high-intensity sparks at the spark plugs, to
ignite the fuel charges in the combustion chambers. The sparks must be
supplied at the right time, and they must have sufficient energy over a
Reproduced by Speciss College with permission from Kevin Sullivan -
range of conditions to ignite the charges. The energy comes from the
battery and alternator, and the voltage is increased by the ignition coil.
The system has two circuits. The primary -or low-tension circuit initiates
the spark. The secondary -or high-tension circuit produces the high
voltage and distributes it to the spark plugs.
Function of the Conventional Ignition System
The conventional ignition system is relatively simple. It consists of two
systems: Low voltage input and high-tension output. When the ignition
switch is turned to the ‗start and run‘ positions, battery voltage is supplied
to the positive side of the induction coil.
The low voltage flows through the primary windings in the coil to the
distributor. Under the distributor cap is a rotor, a set of mechanical
flyweights, a condenser(also called capacitor), set of points, and a
vacuum bowl pull rod (vacuum advance). The distributor shaft has four
cams on a four cylinder engine. Low voltage flows through the points to
ground. The points, which ride on the distributor shaft, open as they peak
on the high points. The condenser is used to keep the points from arcing
upon opening. This prevents premature burning of the points. The
opening of the points causes an open circuit, causing voltage to search
for a new ground. This collapses the magnetic field inside the coil,
inducing voltage into the secondary windings of the induction coil. The
secondary windings increase the voltage. That high-tension voltage (up to
30,000 Volts) now looking for a ground, enters the centre distributor cap
tower via a high-tension wire.
From there it flows through the rotor, to the cap tower of the cylinder that's
at its compression stroke. High-tension voltage flows to the spark plug via
a high-tension wire. When the high-tension voltage reaches the spark
plug, it jumps the gap in the plug to ground. This spark ignites the fuel-air
mixture. As engine RPM increases, the mechanical flyweights adjust the
timing of the ignition according to the engine speed. Engine vacuum is
used to operate the advance pull rod to adjust the timing according to
engine load.
Breaker ignition as described in the above paragraph is found on older
cars uses contact breaker points in a distributor to initiate the spark.
These older system require maintenance and adjustments. They are now
replaced by:
 Electronic ignition. They do not need contact points. When a signal is
received, triggering occurs through transistors in an ignition module.
Reproduced by Speciss College with permission from Kevin Sullivan -
Direct ignition has no distributor and uses coils to supply high-voltage
direct to the spark plugs.
Servicing older ignition systems
On older vehicles it is sometimes still necessary to change/service
contact breaker points and to set the ignition timing.
The following details are an example for a 4 cylinder in-line engine.
Firing order 1-3-4-2 - Static advance 10º - Contact breaker
gap 0.40mm - Dwell angle 55º.
Setting the points can be done simple by adjusting the point‘s gap.
One needs only a feeler gauge. More proficient is the use of a dwell
meter. The dwell angle is set whilst the engine cranks.
Figure 16-2: Checking points gap
Figure 16-3: Timing marks on
crankshaft pulley
Figure 16-4: Connection of a testlamp for static timing
Adjusting the contact breaker points gap
Not only does the points-gap affect the dwell angle but it also affects the
ignition timing. A wide points-gap advances the ignition and too small a
gap retards the ignition. Setting the contact breaker points to the correct
gap is, therefore, to be done before the engine timing is adjusted. Figure
16-2 shows a set of feeler gauges being used to check the gap. The
points-gap is checked with the ignition switched off. The feeler gauge is
inserted between the contacts. If the points-gap is set accurately, the
dwell angle should be correct.
Adjusting the timing can be done statically. The timing angle must be
known and one uses a test-lamp. Easier and more accurate is the
dynamical setting with the engine running by the use of a timing
Reproduced by Speciss College with permission from Kevin Sullivan -
Static timing
When re-setting the static timing after performing work on the engine,
such as on removing and refitting the distributor, it is necessary to ensure
that the piston in the cylinder used for timing (usually number 1) is on the
compression stroke. The firing order helps here, because in this case the
valves on number 4 cylinder will be ‗rocking‘ when number 1 piston is at
top dead centre (TDC) on the compression stroke. The 10º static advance
tells us that the contact breaker points must start to open at 10º before
Engines normally carry timing marks on the crankshaft pulley and these
are made to align with a pointer on the engine block, or timing case, as
shown in Figure 16-3. To position the piston at 10º before TDC, the crank
should be rotated by a spanner on the crankshaft pulley nut, in the
direction of rotation of the engine. This ensures that any ‗free play‘ in the
timing gears is taken up. To make the task more manageable, it is
probably wise to remove the sparking plugs. If the alignment is missed
the first time round, the crank should continue to be rotated in the
direction of rotation until the piston is on the correct stroke and the timing
marks are correctly aligned. When the piston position of number 1
cylinder is accurately set, the distributor should be replaced with the rotor
pointing towards the HT segment, in the distributor cap, that is normally
connected to number 1 sparking plug. This process is made easier on
those distributors that have an off-set coupling.
Setting the timing
A timing light may then be connected between the contact breaker
terminal of the coil and earth. With the ignition switched on and the
contact breaker points closed, the timing lamp will be out. When the
points open, the primary current will flow through the timing light which
will light up. When the correct setting has been achieved, the distributor
clamp should be tightened, the timing light removed and all leads reconnected. The timing light (lamp) can be a light bulb of suitable voltage
(12V) with two leads to which small crocodile clips have been securely
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Chapter 17: Lighting System
Back to ToC
Automotive lighting
The lighting system of a motor vehicle consists of lighting and
signalling devices mounted or integrated to the front, sides, rear, and in
some cases the top of the motor vehicle. The purpose of this system is to
provide illumination for the driver to operate the vehicle safely after dark,
to increase the attention-getting of the vehicle, and to display information
about the vehicle's presence, position, size, direction of travel, and
driver's intentions regarding direction and speed of travel.
Colours of light emitted
The colour of light emitted by vehicle lights is largely standardised by
longstanding conventions. Generally, but with some regional exceptions,
lamps facing rearward must emit red light, lamps facing sideward and all
turn signals must emit amber light, lamps facing frontward must emit
white or selective yellow light, and no other colours are permitted except
on emergency vehicles.
Forward illumination
Forward illumination is provided by high- ("main", "full", "driving") and
low- ("dip", "dipped", "passing") beam headlamps, which may be
augmented by auxiliary fog lamps, driving lamps, and/or cornering lamps.
Dipped beam (low beam, passing beam, meeting beam)
Dipped-beam (also called low, passing, or meeting beam) headlamps
provide a light distribution to give adequate forward and lateral
illumination without blinding other road users. This beam is specified for
use whenever other vehicles are present ahead. Internationally specified
is a beam with a sharp, asymmetric cut-off preventing significant amounts
of light from being cast into the eyes of drivers of preceding or oncoming
Main beam (high beam, driving beam, full beam)
Main-beam (also called high, driving, or full beam) headlamps provide an
intense, centre-weighted distribution of light with no particular control of
glare. Therefore, they are only suitable for use when alone on the road,
as the glare they produce will dazzle other drivers.
Rally and off-road lamps
Vehicles used in rallying, off-roading, or at very high speeds often have
extra lamps to broaden and extend the field of illumination in front of the
vehicle. On off-road vehicles in particular, these additional lamps are
sometimes mounted along with forward-facing lights on a bar above the
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roof, which protects them from road hazards and raises the beams
allowing for a greater projection of light forward.
Front fog lamps
Front fog lamps provide a wide, bar-shaped
beam of light with a sharp cut-off at the top, and
are generally aimed and mounted low. They may Figure 17-1: A pair of yellow fog lamps
be either white or selective yellow. They are
intended for use at low speed to increase the illumination directed
towards the road surface and verges in conditions of poor visibility due to
rain, fog, dust or snow. As such, they are often most effectively used in
place of dipped-beam headlamps, reducing the glare-back from fog.
Spot lights
Police cars, emergency vehicles, and those competing in road rallies are
sometimes equipped with an auxiliary lamp, in a swivelmounted housing attached to the a-pillar, direct-able by a
handle protruding through the pillar into the vehicle.
Front position lamps (parking lamps, standing lamps)
17-2: LED
Night-time standing-vehicles perceptibility is provided by Figure
daytime running lights
"position lamps", known as "parking lamps" or "parking
lights. It is now illegal in many countries to drive a vehicle with parking
lamps illuminated, unless the headlamps are also illuminated.
Daytime Running Lamps
Nordic countries require hardwired Daytime running lamps. DRLs are
permitted in many countries and are seen in Zimbabwe more frequently
on newly imported vehicles.
Turn signals
Turn signals, informally known as "directionals", "blinkers",
"indicators" or "flashers", are signal lights mounted near
the left and right front and rear corners of a vehicle, and
sometimes on the sides, used to indicate to other drivers
that the operator intends a lateral change of position (turn
or lane change). Turn signals are required on all vehicles
that are driven on public roadways in most countries. Figure 17-3: Front
Alternative systems of hand signals were used earlier, and turn signal
they are still common for bicycles. Hand signals are also
sometimes used when regular vehicle lights are malfunctioning.
Side turn signals
In most countries cars must be equipped with side-mounted turn signal
repeaters to make the turn indication visible sideways rather than just to
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the front and rear of the vehicle. In recent years, many automakers have
been incorporating side turn signal devices into the side-view mirror
Electrical connection and switching
Turn signals are required to blink on and off, or "flash", at a steady rate of
between 60 and 120 blinks per minute. Regulations require that all turn
signals activated at the same time (i.e., all right signals or all left signals)
flash in simultaneous phase with one another. Worldwide regulations
stipulate an audiovisual tell-tale indicator when the turn signals are
activated; most commonly by green indicator lights on the vehicle's
instrument cluster, and a cyclical "tick-tack" noise. It is also required that
audio and/or visual warning be provided to the vehicle operator in the
event of a turn signal's failure to light. This warning is usually provided by
a much faster- or slower-than-normal flash rate, visible on the dashboard
indicator, and audible via the faster tick-tack sound. Turn signals are in
almost every case activated by means of a horizontal lever (or "stalk")
protruding from the side of the steering column.
Stop lamps (brake lights)
Red steady-burning rear lights, brighter than the rear position lamps, are
activated when the driver applies the vehicle's brakes. These are called
"stop lamps", or, colloquially, "brake lights". They are required to be fitted
in multiples of two, symmetrically at the left and right edges of the rear of
every vehicle.
Centre High Mount Stop Lamp (CHMSL)
The CHMSL is also sometimes referred to as the "centre brake lamp", the
"third brake light", the "eye-level brake lamp", the "safety brake lamp", or
the "high-level brake lamp". The CHMSL may produce light by means of a
single central filament bulb, a row or cluster of filament bulbs or LEDs.
Reversing lamps
To provide illumination to the rear when backing up, and to warn adjacent
vehicle operators and pedestrians of a vehicle's rearward motion, each
vehicle must be equipped with at least one rear-mounted, rear-facing
reversing lamp (or "backup light).
Rear registration plate lamp
The rear registration plate is illuminated by a white lamp designed to light
the surface of the plate without creating white light directly visible to the
rear of the vehicle; it must be illuminated whenever the position lamps are
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Hazard flashers
Also called "hazards", "hazard warning flashers", "hazard warning lights",
"4-way flashers", or simply "flashers". International regulations require
vehicles to be equipped with a control which, when activated, flashes the
left and right directional signals, front and rear, all at the same time and in
phase. This function is meant to indicate a hazard such as a vehicle
stopped in or near moving traffic, a disabled vehicle and a vehicle moving
substantially slower than the flow of traffic such as a truck climbing a
steep grade, or the presence of stopped or slow traffic ahead on a high
speed road. Operation of the hazard flashers must be from a control
independent of the turn signal control, and an audiovisual tell-tale must be
provided to the driver.
Construction and technology
Light sources:
Traditionally, a tungsten incandescent light bulb
has been the light source used in all of the various
automotive signalling and marking lamps.
Typically, bulbs of 21 to 27watts, are used for
stop, turn, reversing and rear fog lamps, while Figure 17-4: Light source placed in
bulbs of 4 to 10W, are used for tail lamps, parking a parabolic reflector to achieve a
lamps, side-marker lamps and side turn signal directed beam
repeaters. These bulbs typically have either a metal bayonet base or a
plastic or glass wedge base for the physical and electrical interface with
the lamp socket.
Tungsten-halogen light bulbs are a very common light source for
headlamps and other forward illumination functions. Some recent-model
vehicles use small halogen bulbs for exterior signalling and marking
functions, as well.
The devices popularly known as "Xenon headlamps" actually incorporate
Metal halide light sources, and are known as high-intensity discharge, or
HID lamps.
Xenon is currently the lamp used in single-source lighting systems being
developed for automotive use.
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Light emitting diodes (LED)
LEDs are being used with increasing frequency in automotive lamps.
They offer very long service life, extreme vibration resistance, and can
permit considerably shallower packaging compared to most bulb-type
assemblies. LEDs also offer a significant safety performance benefit
when employed in stop lights, for when power is applied they rise to full
intensity approximately 200 milliseconds (0.2 seconds) faster than
incandescent bulbs. Adoption of LEDs beyond the 3rd brake light on
passenger cars has been slow, but is beginning to increase with demand
for the technology and related styling updates. The commercial vehicle
industry has rapidly adopted LEDs for virtually all signalling and marking
functions on trucks and buses, because in addition to the fast rise time
and affiliated safety benefit, LEDs' extremely long service life reduces
vehicle downtime. Almost all commercial vehicles use exterior lighting
devices of standardised format and fitment, which has cost-reduced and
sped the changeover.
LED lamps have been proven to be a feasible alternative to traditional
light sources for flashing beacon lights on vehicles such as maintenance
trucks. The energy-efficient nature of the LED source allows the engine to
remain turned off but the light to continue to flash.
Direction indicators and hazard flashers
The most common problems in the indicators and hazard light circuits are
burned out bulbs, blown fuses, defective flasher units and corroded or
loose connections. The first step in diagnosing a failure is to visually
check the lights. Operate the indicator or hazard lights and walk around
the vehicle, checking to see which lights are not working. Once you've
identified the problem, check all the possible causes in the following list.
If the symptom persists after checking all the possible causes, check the
switch and the wiring, as discussed in the procedure following the
symptom list.
Note: On some vehicles, the turn signal switch and hazard light switch
are wired separately, but the wiring between the switches and lights is
shared. This makes checking the wiring between the switch and the
signal lights simple. For example, if the indicators do not work on one or
both sides, but do work when the hazard lights are turned on, you know
much of the wiring is good.
One indicator on one side doesn't work
1.Check the bulb.
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2.Check for a corroded, worn or damaged bulb socket.
3.Check for a bad earth. Use a jump wire between the earth side of the
bulb and a good chassis earth.
4.Beginning at the non-functioning light and working backward through
the circuit, check for a short or no continuity
Hazard lights or indicators light but don't flash
1. Replace the flasher unit.
Indicators don't light in either direction
1. Check for a blown fuse.
2. Check the bulbs.
3. Check for corroded, worn or damaged bulb sockets.
4. Check for a bad earth. Use a jump wire between the earth side of the
bulbs and a good chassis earth.
5. Replace the flasher unit.
6. Check the turn signal switch.
7. Check for a short or no continuity.
Front and rear lights on one side don't work
1. Check the bulbs.
2. Check for corroded, worn or damaged bulb sockets.
3. Check for bad earths. Use jump wires between the earth sides of the
bulbs and a good chassis earth.
4. Check the turn signal switch (see below).
Flasher rate too fast or too slow
1. Make sure the correct flasher unit is installed.
2. Make sure the correct bulbs are installed.
3. If the rate is too fast, check for an overcharging condition. If the rate is
too slow, check for a weak battery or an undercharging condition.
Indicator light(s) on dashboard don't flash, only glow
1. Check the lights with the circuit turned on.
2. If the lights are also glowing steadily, replace the flasher.
3. If the lights are not on, check the light bulb.
4. Check for a corroded, worn or damaged bulb socket.
5. Check for a bad earth. Use a jump wire between the earth side of the
non-functioning light(s) and a good chassis earth.
6. Beginning at the non-functioning light(s) and working backward
through the circuit check for an open (no continuity).
Indicators work but hazard lights don't
1. Replace the hazard flasher.
2. Check for a faulty hazard flasher switch.
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Brake lights
One brake light does not work, but others do
1. Check the bulb.
2. Check the bulb socket for corrosion, damage and worn terminals.
3. Check for a bad earth connection by hooking up a jump wire between
the earth terminal of the non-functioning light and a good chassis
earth. If the light now works, repair the faulty earth connection.
4. Beginning at the non-functioning light and working backward through
the circuit, check for a short or no continuity.
No brake lights work
1. Check the fuse and check for corrosion at the fuse terminals.
2. Check the brake light switch (see below).
3. Check for a bad earth at the brake light bulbs, burned out bulbs and
corroded or loose connections.
Brake light bulbs bum out quickly
1. Check for an overcharging condition.
Headlight Aiming Adjustment
Headlight Adjustment
If you remove the headlights or change the bulbs, the headlights may be
out of alignment. They may be too low or dazzling drivers.
Before performing aiming adjustment, make sure of the following.
1. Keep all tires inflated to the correct pressure.
2. Place the vehicle on level ground and press the front bumper & rear
bumper down several times.
3. See that the vehicle is unloaded (except for full levels of coolant,
engine oil and fuel, and spare tire, jack and tools).
4. Clean the head lights lens and turn on the headlight (Lower beam).
5. Open the hood.
6. If needed, adjust the vertical indicator by turning the adjusting device.
7. If needed, adjust the horizontal indicator by turning the adjusting
How Do I Know If/When the Lights Are Correctly Aligned?
Without the correct equipment it's impossible to be 100% accurate but a
good guess is better than illuminating the moon or oncoming traffic. Pull
up close to a wall or fence. Use a marker or a bit of tape to make 2 X's
aligned to the centre of the two dipped beam bulbs. Pull the back away
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from the wall so the headlights are 5 meters away from the X's. Using the
adjusters on the headlights, move the projected light so the cut off line is
5cm below the centre of the X. That is the vertical alignment sorted.
Each light beam will have an up-turn that travels up and off to the left (on
RHD cars).This up-turn needs to start about the same distance from the
X on both sides. That is the horizontal alignment sorted.
Ideally you need to go to a vehicle inspection department station and get
them to use their beam setter.
Figure 17-5: Correct pattern of low-beam light with car 5m distance from test wall
Reproduced by Speciss College with permission from Kevin Sullivan -
Chapter 18: Wiring diagrams
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Using the Electrical Wiring Diagram (Toyota Examples)
One of the keys to a quick and successful electrical diagnosis is correctly
using the electrical Wiring Diagram or EWD. The EWD is not just a book
of wiring diagrams, but an information resource for anything electrical on
the vehicle. Everything from connector ID and location to what circuits
share splice points is included in this manual.
Because there is so much information, it takes a little practice to learn
where it is located, and what each of the EWD symbols and individual
sections can tell you. We will take a detailed look at all of these features,
and how to use them in diagnosing an electrical problem.
Sections of Toyota ‘Electrical Wiring Diagram’
Composition and contents of wiring diagrams
Figure 18-1: The EWD is built around the use of the System Circuit Diagrams. These
wiring diagrams provide “circuit road maps" for individual circuits or systems on
the vehicle.
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 The EWD consists of wiring harness diagrams, installation locations of
individual parts, circuit diagrams and index.
 In each section, all specifications are listed, including optional specifications.
Accordingly, some specifications may not be applicable for individual vehicles.
This EWD manual provides information on the electrical circuits installed
on vehicles by dividing them into a circuit for each system.
The actual wiring of each system circuit is shown from the point where the
power source is received from the battery as far as each ground point.
(All circuit diagrams are shown with the switches in the OFF position.)
When troubleshooting any problem, first understand the operation of the
circuit where the problem was detected (see System Circuit section), the
power source supplying power to that circuit (see Power Source section),
and the ground points (see Ground Point section).
See the System Outline to understand the circuit operation.
When the circuit operation is understood, begin troubleshooting of the
problem circuit to isolate the cause.
Use Relay Location and Electrical Wiring Routing sections to find each
part, junction block and wiring harness connectors, wiring harness and
wiring harness connectors, splice points, and ground points of each
system circuit.
Internal wiring for each junction block is also provided for better
understanding of connection within a junction block. Wiring related to
each system is indicated in each system circuit by arrows (from -, to -).
When overall connections are required, see the Overall Electrical Wiring
Diagram at the end of this manual.
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How to Read Wiring Diagrams (Example Toyota EWD)
Stop light circuit on page 7 (out of the 27 pages) in the System
Circuit Section H:
Examples from Section K of the EWD illustrating various connectors
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Full Stop Light circuit diagram from EWD -with details (A – M)
explained on the next page-
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Details A – M explained from previous page:
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Two page overview explaining all components of the circuit
diagram (left page)
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Two page overview explaining all components of the circuit
diagram (right page)
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Another example of a typical Circuit Diagram
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Chapter 19: Gauges, Warning Devices & Driver Info
Back to ToC
This chapter covers the operation and common circuits of gauges,
warning devices, and driver information systems. These systems include
cooling fans, electromagnetic instrument circuits (sending and receiving
gauges), and electronic instrument circuits (driver information systems).
Electromagnetic Instrument Circuits
Gauges and warning lamps allow the driver to monitor a vehicle‘s
operating conditions. These instruments differ widely from car to car, but
all are analog. Digital electronic instruments are explained in the
―Electronic Instrument Circuits‖ section in this chapter. Warning lamps
are used in place of gauges in many cases because they are less
expensive and easier to understand, although they do not transmit as
much useful information as gauges do. The following paragraphs explain
the general operation of analog gauges, lamps, and the sending units that
control them.
Gauge Operating Principles
Common gauges use one of the following three operating principles:
 Mechanical
 Bimetallic (thermal-type)
 Electromagnetic
Mechanical gauges are operated by cables, fluid pressure, or fluid temperature.
Because they do not require an electrical circuit, they do not fit into our study.
The cable-driven speedometer is the most common mechanical gauge.
Bimetallic Gauges
A bimetallic gauge works by allowing current to flow through the
bimetallic strip and heat up one of the metals faster than the other,
causing the strip to bend. A typical gauge (Figure 19-1) has U-shaped
bimetallic piece anchored to the gauge body at the end of one arm. The
other arm has a high-resistance wire (heater coil) wound around it.
Current flow through the heater coil bends the free bimetallic arm. Varying
the current changes the bend in the arm. A pointer attached to the moving
arm can relate the changes in current to a scale on the face of the gauge.
Ambient temperature could affect the gauge, but the U-shape of the
bimetallic strip provides temperature compensation. Although ambient
temperature bends the free arm in one direction, the fixed arm is bent in
the other direction and the effect is cancelled.
Reproduced by Speciss College with permission from Kevin Sullivan -
Figure 19-1: The bimetallic gauge
depends upon the heat of current
flow bending a bimetallic strip.
Figure 19-2: The Galvanometer
movement uses the field interaction
of a permanent magnet and an
Figure 19-3: In a three-coil gauge, the
variable resistance-sending unit affects
current flow through three interacting
Electromagnetic Gauges
The movement of an electromagnetic gauge depends on the interaction
of magnetic fields. The following kinds of movements are commonly used:
• Galvanometer movement
• Three-coil or two-coil movement
• Air core design
A Galvanometer movement has a movable electromagnet surrounded
by a permanent horseshoe magnet (Figure 19-2). The electromagnet‘s
field opposes the permanent magnet‘s field, causing the electromagnet to
rotate. A pointer mounted on the electromagnet relates this movement to
a scale on the face of the gauge. The amount of current flow through the
electromagnet‘s coil determines the electromagnet‘s field strength, and
therefore the amount of pointer movement.
A three-coil movement depends upon the field interaction of three
electromagnets and the total field‘s effect on a movable permanent
magnet. The circuit diagram of a typical three-coil movement (Figure 193) shows that two coils are wound at right angles to each other. These
are the minimum-reading coil and the maximum-reading coil. Their
magnetic fields will pull the permanent magnet and pointer in opposite directions.
A third coil is wound so that its magnetic field opposes that of the minimumreading coil. This is called the bucking coil. The three coils are connected in
series from the ignition switch to ground. A fixed resistor forms a circuit branch
parallel to the minimum-reading coil. The variable-resistance-sending unit forms a
circuit branch to ground, parallel to the bucking and minimum-reading coils.
When the sending resistance is high, current flows through all three coils to
ground. Because the magnetic fields of the minimum-reading and the bucking
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coils cancel each other, the maximum reading coil‘s field has the strongest effect
on the permanent magnet and pointer. The pointer moves to the maximumreading end of the gauge scale.
As sending unit resistance decreases, more current flows through the minimumreading coil and the sending unit to ground than flows through the bucking and
maximum-reading coils. The minimum-reading coil gains a stronger effect upon
the permanent magnet and pointer, and the pointer moves to the minimumreading end of the gauge scale.
The design of two-coil gauges varies with the purpose for which the gauge is
used. In a fuel gauge, for example, the pointer is moved by the magnetic fields of
the two coils positioned at right angles to each other. Battery voltage is applied to
the E (empty) coil and the circuit divides at the opposite end of the coil. One path
travels to ground through the F (full) coil; the other grounds through the sender‘s
variable resistor. When the sender resistance is low (low fuel): Current passes
through the E coil and the sender resistor to move the pointer toward E on the
scale. When the sender resistance is high (full tank): Current flows through the F
coil to move the pointer toward F on the scale.
When a two-coil gauge is used to indicate coolant temperature, battery voltage
is applied to both coils. One coil is grounded directly; the other grounds through
the sending unit. Sender resistance causes the current through one coil to
change as the temperature changes, moving the pointer.
In the air-core gauge design, the gauge receives a varying electrical signal
from its sending unit. A pivoting permanent magnet mounted to a pointer aligns
itself to a resultant field according to sending unit resistance. The sending unit
resistance varies the field strength of the windings in opposition to the reference
windings. The sending unit also compensates for variations in voltage.
This simple design provides several advantages beyond greater accuracy. It
does not create radiofrequency interference (RFI), is unaffected by temperature,
is completely noiseless, and does not require the use of a voltage limiter. Like the
three- and two-coil designs, however, the air-core design remains at its last
position when the ignition switch is turned off, giving a reading that should be
Instrument Voltage Regulator
On early-model cars and imported vehicles, except for the air core
electromagnetic design, gauges required a continuous, controlled amount
of voltage. This is usually either the system voltage of 12 volts or a
regulated 5–6 volts. An instrument voltage regulator (IVR) supplied that
regulated voltage. The IVR can be a separate component that looks much
like a circuit breaker or relay; it can also be built into a gauge. Its
bimetallic strip and vibrating points act like a self-setting circuit breaker to
keep the gauge voltage at a specific level. Gauges that operate on limited
voltage can be damaged or give inaccurate readings if exposed to full
system voltage.
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Warning Lamp Operating Principles
Warning lamps alert the driver to potentially hazardous vehicle operating
conditions, such as the following:
High engine temperature - Low oil pressure - Charging system problems - Low
fuel level - Low brake fluid level - Parking brake on - Seat belts not fastened Exterior lighting failure ect.
Warning lamps can monitor many different functions but are usually activated in
one of the following four ways:
 Voltage drop
 Grounding switch
 Ground sensor
These three methods are used to light a bulb or an LED mounted on the dash
Voltage Drop
A bulb will light only if there is a voltage drop across its filament. Warning
lamps can be installed so that equal voltage is applied to both bulb
terminals under normal operating conditions. If operating conditions
change, a voltage drop occurs across the filament, and the bulb will light.
(E.g. charging system indicators)
Grounding Switch
A bulb connected to battery voltage will not light unless the current can flow to
ground. Warning lamps can be installed so that a switch that reacts to operating
conditions controls the ground path. Under normal conditions, the switch contacts
are open and the bulb does not light. When operating conditions change, the
switch contacts close. This creates a ground path for current and lights the bulb.
Figure 19-4: The oil pressure sending unit
provides a varying amount of resistance as
engine oil pressure changes.
Figure 19-5: This oil pressure grounding switch
has a fixed contact and a contact that is moved
by the pressure-sensitive diaphragm.
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Ground Sensor
A ground sensor is the opposite of a ground switch. Here, the warning lamp
remains unlit as long as the sensor is grounded. When conditions change and the
sensor is no longer grounded, the bulb lights. Solid-state circuitry generally is
used in this type of circuit.
Specific Instruments
Many different instruments have appeared in automobiles, but certain
basic functions are monitored in almost all cars. Normally, a car‘s
instrument panel will contain at least the following:
 An ammeter, a voltmeter, or an alternator warning lamp
 An oil pressure gauge or warning lamp
 A coolant temperature gauge or warning lamp
 A fuel level gauge
The following paragraphs explain how these specific instruments are
constructed and installed.
Figure 19-6: Coolant temperature gauge
Figure 19-7: The fuel tank sending unit
has a float that moves with the fuel
level in the tank and affects a variable
Charging System Indicators
Usually a warning lamp light shows an undercharged battery or low voltage from
the alternator.
Ammeters are found in some up-market vehicles.
Oil Pressure Gauge or Warning Lamp
The varying current signal to an oil pressure gauge is supplied through a
variable-resistance sending unit that is exposed to engine oil pressure. The
resistor variation is controlled by a diaphragm that moves with changes in oil
pressure, as shown in Figure 19-4.
An oil pressure-warning lamp lights to indicate low oil pressure. A ground switch
controls the lamp as shown in Figure 19-5. When oil pressure decreases to an
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unsafe level, the switch diaphragm moves far enough to ground the warning lamp
circuit. Current then can flow to ground and the bulb will light.
Oil pressure warning lamps can be operated by the gauge itself.
When the pointer moves to the low-pressure end of the scale, it closes contact
points to light a bulb or an LED.
Temperature Gauge or Warning Lamp
In most late-model cars, the temperature gauge ending unit is a thermistor
exposed to engine coolant temperature, as shown in Figure 19-6. As coolant
temperature increases, the resistance of the thermistor decreases and current
through the gauge varies.
Fuel Gauge or Warning Lamp
All modern cars have a fuel level gauge. A variable resistor in the fuel tank
provides current control through the fuel gauge. The fuel tank sending unit has a
float that moves with the fuel level, as shown in Figure 19-7. As the float rises
and falls, the resistance of the sending unit changes. If a low-fuel-level indicator
is used, its switch may operate through a heater or bimetallic relay to prevent
flicker. Fuel level warning lamps are operated by the action of the fuel gauge
Chapter 20: Connector Repair
Back to ToC
Terminal and Connector Repair
Figure 20-1: Location and type
of locking devices
Figure 20-2: Releasing locking clip
Figure 20-3: Select correct
replacement terminal
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Step 1. Identify the connector and terminal type.
Replacing Terminals
Identify the connector name, position of the locking clips, the un-locking
direction and terminal type from the pictures provided on the charts.
Step 2: Remove the terminal from the connector.
Disengage the secondary locking device or terminal retainer.
 Locking device must be disengaged before the terminal locking clip can
be released and the terminal removed from the connector.
 Use a miniature screwdriver or the terminal pick to unlock the
secondary locking device.
Determine the primary locking system from the charts.
 Lock located on terminal
 Lock located on connector
 Type of tool needed to unlock
 Method of entry and operation
Step 3.Remove terminal from connector by releasing the locking
a. Push the terminal gently into the connector and hold it in this position.
b. Insert the terminal pick into the connector in the direction shown in the
c. Move the locking clip to the un-lock position and hold it there.
NOTE: Do not apply excessive force to the terminal.
Do not pry on the terminal with the pick.
d. Carefully withdraw the terminal from the connector by pulling the lead
toward the rear of the connector.
Step 4. Replace damaged terminal
 Measure "nominal" size of the wire lead by with a Vernier Calliper.
 Select the correct replacement terminal, with lead, from the repair kit
or cannibalized harness.
 Cut the old terminal from the harness.
 Use the new wire lead as a guide for proper length.
 Strip insulation from wire on the harness and replacement terminal
lead. Strip length should be approximately 8 to 10 mm.
 Create proper slice connection with isolated crimp-on connector or
soldering splice, covered by heat shrink tube.
 Install the terminal into the connector.
Reproduced by Speciss College with permission from Kevin Sullivan -
 Check that the locking clip is good condition and in the proper position.
If it is on the terminal and not in the proper position, use the terminal
pick to gently bend the locking clip back to the original shape.
 Check that the other parts of the terminal are in their original shape.
Figure 20-4: Undamaged terminal with lead
replaces damaged one
Chapter 21: Accessories: Wiper, Washer and Horn
Windshield wipers and washers
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Laws require that all cars have both a two-windshield wiper system and a
windshield washer system. Modern wiper systems are operated by electric
motors. The washer system can be manually operated, or it can have an electric
pump. Many vehicles also have a single-speed wiper and washer for the rear
window. This is a completely separate system, but it operates in the same way as
the windshield wiper and washer system.
Reproduced by Speciss College with permission from Kevin Sullivan -
Circuit Diagram
Figure 21-1: Complete Wiper / Washer Circuit (Toyota)
A typical two-speed wiper system circuit diagram is shown in Figure 21-1. The
motor fields are permanent magnets. The wiper switch controls both the wiper
motor speeds and the washer pump. The park switch within the wiper motor
ensures that when the wiper switch is turned off, the motor will continue to turn
until the wiper arms have reached the bottom edge, or park position, of the
windshield. The circuit shown has a circuit breaker built into the wiper switch. The
Reproduced by Speciss College with permission from Kevin Sullivan -
circuit breaker also can be a separate unit, or it can be mounted on the wiper
The wiper switch is between the power
source and the grounded wiper motor. The
wiper switch does not receive current unless
the ignition switch is turned to the ‗Accessory‘
or the ‗Run‘ position.
The wiper switch may be mounted on the
instrument panel, or it can be mounted in the
steering column and controlled by a
multifunction lever or stalk.
Figure 21-2: The washer switch is usually
a spring-loaded pushbutton mounted on
the instrument panel or on a multifunction
Most two-speed wiper motors use permanent ceramic magnets as pole
pieces. Three brushes ride on the motor‘s commutator. One brush is a
common, or shared, brush and conducts current whenever the wiper
motor is operating. The other brushes are placed at different positions
relative to the motor armature. Current through one brush produces a
different motor speed than current through the other brush. The wiper
switch contacts route current to one of these two brushes, depending
upon which wiper motor speed the driver selects.
Windshield wiper and washer circuits have many variations. They can
include a permanent magnet motor or one with electromagnetic fields.
The park position can be at the bottom edge of the windshield or below
the bottom edge. An intermittent wipe feature can be driver or speedcontrolled. Each of these variations requires slightly different circuitry.
Washer pumps can be mounted at the cleaner reservoir or on the wiper
motor. Pumps are not serviced, but are replaced.
Figure 21-3: Horn function
Reproduced by Speciss College with permission from Kevin Sullivan -
Signal Horn
An automotive horn circuit can be a simple
series circuit, or it can use a relay to control
current through the horns. The horn switch is a
normally open push-pull switch that is operated
by the driver.
Automotive horns use electromagnetism to
vibrate a diaphragm and produce sound
waves. A typical horn contains normally closed
contact points in series with a coil. One of the
contact points is mounted on a movable
armature to which the horn diaphragm is
Figure 21-4: Signal Horn circuit with
The horn coil is in series with the horn switch relay
or horn relay contacts. When the horn switch or horn relay contacts close,
current flows through the horn coil to ground. The electromagnetic field
created by the coil attracts the armature, also moving the diaphragm. The
armature movement opens the contact points, which open the coil circuit.
With no magnetic field to hold them, the armature and diaphragm move
back to their normal positions. The points are again closed, allowing
current to flow through the coil. This opening and closing of the
electromagnetic circuit is causing the horn diaphragm to vibrate. Since this
cycle occurs very rapidly, the resulting rapid movements of the diaphragm create
sound waves. The speed or frequency of the cycling determines the pitch of the
sound created.
Chapter 22: Enhance Vehicle Electrical Systems
Accessory Lighting
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Every car manufacturer offers unique accessory lighting circuits. These range
from hand-controlled spotlights to driving and fog lamps. Each additional
accessory circuit requires more bulbs, more wiring, and possibly an additional
There are rules for the aftermarket installation of fog lamps or spot lamps. Safe
wiring and proper fusing is most important for trouble free operation. The use of
relays is ensuring that there is no undesirable
voltage drop in the plus supply of the lamps. But
there are also legal considerations. For example
extra spot lamps have to be connected that the
work only combined with the driving lights.
Figure 22-1: Four way connector
Reproduced by Speciss College with permission from Kevin Sullivan -
Trailer Wiring Connectors
Various connectors are available from four to seven pins that allow for the
transfer of power for the lighting as well as auxiliary functions such as an
electric trailer brake controller, backup lights, or a 12V power supply for a
winch or interior trailer lights.
4-Way Connectors
4-Way connectors are available allowing the basic hook-up of the three
lighting functions (running, turn, and brake lights) plus one pin is provided
for a ground wire. Most standard light duty trailers will use a 4-pole flat
7-Way Connectors
Aside from the three main lighting functions, additional pins for electric
brakes, a 12 volt "hot" lead, and backup lights are available. There are
two types of 7-way connectors. One has flat pins, which is often referred
to as blades. The other one has round pins. The round pin style is very
rare. The RV style 7-way with flat pins (or blades) is very common. It is
often found on newer trucks and SUVs that come equipped from the
factory with a trailer hitch.
Figure 22-2: Trailer wiring with 7 way connector
Figure 22-3: Pin lay-out and cable colours 7 way connector
Reproduced by Speciss College with permission from Kevin Sullivan -
Alarm systems
Vehicle alarm systems are often incorporated into a complete vehicle
security package including an immobiliser and central deadlocking. In
addition, they can be retro-fitted to increase the security of older or highrisk vehicles. The main function of the alarm system is to emit a warning
signal when an unauthorised attempt is made to enter the vehicle or
tamper with it. Typically the warning signal consists of a siren and flashing
hazard lights.
A number of technologies are utilised to protect the vehicle and interior:
 Contact switches at the door, boot and bonnet.
 Ultrasonic interior sensor: using interior-mounted transceivers, the
inside of the passenger compartment is flooded with an ultrasonic field.
Any disturbance (due to breakage of glass, illegal entry) changes the
amplitude and phase of the ultrasonic signal and this triggers the
 Microwave interior sensor: similar to the above but a higher-frequency
signal that is less susceptible to false alarms. This is often used in softtop/cabriolet vehicles.
 Shock sensor: a piezo-electric accelerometer senses impacts and
vibration on the vehicle structure.
 Tilt detection: changes in vehicle position, including rate of change, are
monitored. If these exceed a threshold (due to illegal movement of the
vehicle) then the alarm is triggered.
 Voltage drop: the rate of change of the battery voltage is monitored,
and if significant current is drawn (e.g. for the interior light or ignition)
the alarm is triggered.
Figure 22-4: Remote Keyless
Entry (RKE) or Remote Lock
Control (RLC) transmitter.
Reproduced by Speciss College with permission from Kevin Sullivan -
Figure 22-5: Block diagram of a complex alarm system
Figure 22-6: Components of an alarm system
Chapter 23: Outlook on Topics in Diploma Course
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The previous chapters covered the syllabus of the Speciss-Auto Electrics
Certificate course.
Advanced topics, like listed below, are taught in the Speciss-Auto
Electrics Diploma course:
 Principles of Electronics,
 Electronic Ignition,
 Electronic Fuel Injection,
 Multiplexing in Auto Electric Systems,
 CAN/BUS Data Management
 OBD Diagnosis Principles and Codes
Principles of electronics
As an Auto Electrician, you will often find yourself working with electrical
systems and occasionally having to troubleshoot them as well. Therefore,
having a thorough understanding of basic electronic principles will be
essential somewhere in your line work.
You should understand the fundamentals of electronics as well as
introduce some of the more common electronic circuits and components.
Some common test equipment as well as circuit analysis and
troubleshooting methods used in the field of electronics should be
Before you can effectively troubleshoot an electronic system, it is vital for
you to understand some of the basic concepts and principles of
Reproduced by Speciss College with permission from Kevin Sullivan -
The following topics are covered in the Speciss-Auto Electrics Diploma
• identify and locate components of electronic circuits, ECU‘s, ‗black
boxes‘, sensors and actuators and their connecting wiring.
• explain the behaviour and application of capacitors
• explain the p and n junction
• describe behaviour of a silicon diode
• explain the behaviour and application of Thermistors (NTC, PTC)
• describe use of diodes in vehicles: rectification, de-spiking, isolation of
• describe use of LEDs as pilot lamps, signalling and lighting source
• explain basic operation of a transistor
• describe different transistor applications
• explain transistor gain and use in integrated circuits
• classify analogue and digital signals
• draw analogue and digital wave forms.
• name main function of microprocessors, RAM and ROM memory.
• explain function and draw symbols of logical gates like AND, OR,
Electronic Ignition
Figure 23-1: Layout of an electronic ignition
The disadvantage of the mechanical system is the use of breaker points
to interrupt the low-voltage high-current through the primary winding of
the coil; the points are subject to mechanical wear where they ride the
cam to open and shut, as well as oxidation and burning at the contact
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surfaces from the constant sparking. They require regular adjustment to
compensate for wear, and the opening of the contact breakers, which is
responsible for spark timing, is subject to mechanical variations.
In addition, the spark voltage is also dependent on contact effectiveness,
and poor sparking can lead to lower engine efficiency. A mechanical
contact breaker system cannot control an average ignition current of more
than about 3 A while still giving a reasonable service life and this may
limit the power of the spark and ultimate engine speed.
Example of a basic electronic ignition system
Electronic ignition (EI) solves these problems. In the initial systems,
points were still used but they handled only a low current which was used
to control the high primary current through a solid state switching system.
Soon, however, even these contact breaker points were replaced by an
angular sensor of some kind, commonly using a Hall Effect sensor, which
responds to a rotating magnet mounted on the distributor shaft. The
sensor output is shaped and processed by suitable circuitry, then used to
trigger a switching device such as a Darlington transistor, which switches
a large current through the coil.
Electronic fuel injection
Electronic Fuel injection works on some very basic principles. The
following discussion broadly outlines how a basic or Convention
Electronic Fuel Injection (EFI) system operates.
The Electronic Fuel Injection system can be divided into three: basic subsystems. These are the fuel delivery system, air induction system, and
the electronic control system.
Reproduced by Speciss College with permission from Kevin Sullivan -
Figure 23-2: BOSCH electronic fuel injection with air mass meter
The Fuel Delivery System
• The fuel delivery system consists of the fuel tank, fuel pump, fuel filter,
fuel delivery pipe (fuel rail), fuel injector, fuel pressure regulator, and fuel
return pipe.
• Fuel is delivered from the tank to the injector by means of an electric
fuel pump. The pump is typically located in or near the fuel tank.
Contaminants are filtered out by a high capacity in line fuel filter.
• Fuel is maintained at a constant pressure by means of a fuel pressure
regulator. Any fuel which is not delivered to the intake manifold by the
injector is returned to the tank through a fuel return pipe.
The Air Induction System
• The air induction system consists of the air cleaner, air flow meter,
throttle valve, air intake chamber, intake manifold runner, and intake
• When the throttle valve is opened, air flows through the air cleaner,
through the air flow meter past the throttle valve, and through a well
tuned intake manifold to the intake valve.
• Air delivered to the engine is a function of driver demand. As the throttle
valve is opened further, more air is allowed to enter the engine cylinders.
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• There are two different methods to measure intake air volume. One type
of EFI systems measures the air flow directly by using an air flow meter.
Another type of EFI system measures the air flow indirectly by
monitoring the pressure in the intake manifold.
Electronic Control System
• The electronic control system consists of various engine sensors,
Electronic Control Unit (ECU), fuel injector assemblies, and related
• The ECU determines precisely how much
fuel needs to be delivered by the injector
by monitoring the engine sensors.
• The ECU turns the injectors on for a
precise amount of time, referred to as
injection pulse width or injection duration,
to deliver the proper air/fuel ratio to the
Multiplexing in auto-electric
A multiplex network reduces the number of
wires in the wiring harness and greater
Figure 23-3: CAN/BUS in new passenger car
vehicle content flexibility.
Even the most basic vehicles include many
electronically controlled systems. If each electronic system had its own
ECU, harness and sensors, the weight of the added components would
negate any efficiency it provided. A vehicle‘s multiple electronic systems
could require over 1.6 kilometers of insulated wiring, consisting of around
1000 individual wires and many terminals.
One solution to the problem is the use of a system that integrates sensors
into a common wiring harness by combining all the individual systems,
where possible, into a multiplexed serial communications network, so
they can share the information.
An added advantage of such a system is that if there is less wire and
fewer connections there is less chance of dirty connections causing
Also, networking allows greater vehicle content flexibility because
functions can be added or modified through software changes.
Other control units can be added to the system by simply connecting
them to the network.
Reproduced by Speciss College with permission from Kevin Sullivan -
A diagnostic tool can be connected to the CANBUS to extract operational
information to assist in diagnosis and fault finding.
CAN/BUS data management
This system is referred to as a Controlled Area Network BUS or CAN
BUS and it uses two thin wires to connect, or multiplex, all the control
units and their sensors to each other. The output devices are referred to
as Nodes.
The advantage of a multiplex network is that it enables a decreased
number of dedicated wires for each function, and therefore a reduction in
the number of wires in the wiring harness, reduced system cost and
weight, improved reliability, serviceability, and installation. In addition,
common sensor data, such as vehicle speed, engine temperature, etc.
are available on the network, so data can be shared, thus reducing the
number of sensors.
OBD diagnosis
On-Board Diagnostic systems use the
vehicle‘s computers to detect problems with its
emission components and other systems. It
informs the vehicle operator when a fault
occurs and assists the technicians in
identifying and repairing malfunctioning
Figure 23-4: Data display from OBD (On
There are two different types of On Board Board Diagnosis)
Diagnostic systems. OBD 1, which operates
under manufacturer standards and OBD 2, which operates under a
standard set by the Society of Automotive Engineers. OBD I is a system
that identifies faults in the vehicle‘s emission and power-train.
It has been superseded by OBD II, an enhanced On-Board diagnostic
system that identifies faults in the vehicle‘s emission and power-train and
also tests the vehicles operational system to determine faults that do not
affect the vehicles drivability but may affect its safety or emission
Reproduced by Speciss College with permission from Kevin Sullivan -
Appendix A
Wiring Diagram Symbols
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(Japanese cars)
Reproduced by Speciss College with permission from Kevin Sullivan -
Cont. Wiring Diagram Symbols
(Japanese cars)
Reproduced by Speciss College with permission from Kevin Sullivan -
Appendix B
Glossary of Terms
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A − Abbreviation for ampere, the unit of measurement of current.
Active Materials − The metals and acids used in a storage battery which
cause a chemical reaction to occur and voltage potential to be developed.
Afterglow − The time the glow plugs remain activated after fuel in a
diesel engine starts to self-ignite. The added heat is used to reduce white
smoke and improve slow idle.
Alternating Current (AC) − An electric current whose polarity is
constantly cycling between positive and negative. (Reverse direction or
flow at regular intervals.)
Alternator − A type of generator used in automobiles to produce electric
current. Its A.C. (Alternating Current) output is internally rectified
(changed) to D.C. (Direct Current) through the use of diodes.
Ammeter − An electrical meter used to measure the amount of current
flowing in a circuit. It reads amperes of current flow. The ammeter must
be connected in series with the circuit ... red lead toward the voltage
source, black lead toward ground.
Amperage − The amount of current (amperes) flowing in a circuit.
Ampere − The unit of measure for the flow of electrons, or current, in a
circuit. The amount of current produced by one volt acting against one
ohm of resistance.
Ampere Hour − Unit used to rate batteries. The quantity of electricity
delivered by a current of one ampere flowing for one hour.
Ampere-Hour Rating − A battery rating based on the amperes of current
that a battery can supply steadily for 20 hours, with no battery cell falling
below 1.75 volts. Also called a 20−hour discharge rating.
Ampere Turn − The amount of magnetism or magnetizing force
produced by a current of one ampere flowing around a coil of one turn.
The product of the current flowing through a coil multiplied by the number
of turns or loops of wire in a coil.
Analogue − Method of transmitting information through an electrical
circuit by regulating or changing the current or voltage.
Anode − Positive terminal or electrode through which current flows in a
Armature − Conductor or coil of wire moved through a magnetic field to
produce current. In an alternator, the rotor is a magnetic field that rotates
inside the stator coils to induce voltage in them. In a motor, it is the
Reproduced by Speciss College with permission from Kevin Sullivan -
rotating electromagnetic field interacting with the stationary magnets to
produce a turning motion.
Armature Circuit Tests − Tests used to determine if there are any short
circuits or opens and grounds in the armature of a starter motor.
Atom − The small particles which make up all matter. An atom is made
up of a positive-charged nucleus with negative-charged electrons orbiting
around it.
Ballast (Primary) Resistor − A resistor in the primary circuit that
stabilizes ignition system voltage and current flow.
Bar Magnet − A straight permanent magnet.
Base − The centre layer of semiconductor material in a transistor.
Battery − A group of two or more cells of a lead-acid (storage) battery
connected together. It produces an electric current by converting
chemical energy into electrical energy. Also, a dry cell.
Battery Acid − Mixture of sulfuric acid and water used in a storage
battery. Also called the battery electrolyte.
Battery Cell − Group of positive and negative plates, covered with
electrolyte, in a compartment of the battery case separate from other
elements. A cell of an automotive battery has a voltage of about 2.2 volts.
Battery Charge − Reverse chemical reaction that takes place when
current is reversed through a battery to restore the metal in the plates and
the electrolyte to their original condition.
Battery Charger − Rectifier used to change alternating current into direct
current to send a reverse current through the plates of a battery to restore
the chemical imbalance needed to produce electrical energy.
Battery Element − Group of positive and negative plates with separators
and covered with electrolyte and contained in a battery cell.
Belt Tension − The tightness of a drive belt.
Biasing − Applying voltage to a junction of semiconductor materials.
Bimetal − Sensing device made from two metals with different heat
expansion rates. Temperature changes cause the device to bend or
distort. Activates another component.
Bimetallic − A substance made up of two metals bonded together.
Bonding − Process by which the electrons in the valence ring of one
atom are shared with those of another.
Bound Electrons − Five or more tightly held electrons in an atom‘s outer
Breakdown Voltage − Voltage applied to a diode or a transistor in the
reverse direction from that in which it passes current. The voltage is large
Reproduced by Speciss College with permission from Kevin Sullivan -
enough to cause a massive failure to hold back current. Breakdown
voltage is also that applied to a zener diode to allow a reverse current
flow through the diode.
Brushes − Bars of carbon, or other conductive material, that make an
electrical connection with the rotating commutator or slip rings.
Bus Bar − A solid metal strip, or bar, used as a conductor in a fuse panel.
Cable − Conductor made from a number of wires twisted together.
Capacitance − The ability of two conducting surfaces, separated by an
insulator, to store an electric charge.
Capacitor − Electrical component used to store and release a current
through a secondary circuit. Can be used to protect a circuit against
surges in current, store and release a high voltage, or smooth out current
fluctuations. Also called a condenser.
Capacity Test − Test of a battery‘s condition by applying a heavy load
(300 amp) to the battery for a brief time (15 seconds) then measuring the
Carbon Pile − A pile, or stack, of carbon disks enclosed in an insulating
tube. When the disks are pressed together, the resistance of the pile is
Cathode − The negative terminal of a semiconductor toward which the
current flows.
Cell − A dry cell, e.g., a flashlight battery. In a storage (wet cell) battery,
one of the sets of positive and negative plates which, with electrolyte
(sulfuric acid and water), produces electricity. Each cell can produce
about 2.2 volts.
Cell Gassing − The emission of hydrogen gas from battery cells during
Central Processing Unit (CPU) or Microprocessor − The processing and
calculating portion of a microcomputer.
Charge (Recharge) − To restore the active materials in a battery cell by
electrically reversing the chemical action.
Charging System − Components to restore electrical potential in the
battery and supply the current needed to meet the electrical demands of
the vehicle.
Circuit − A combination of elements physically connected to provide an
unbroken flow of electrical energy from a power source through a
conductor to a working device, and through a return conductor, back to
the power source.
Reproduced by Speciss College with permission from Kevin Sullivan -
Circuit Breaker − Device used to open an electric circuit when
overheated to prevent damage by excess current flow.
Circuit Diagram − Drawing showing the wires, connections and
components (loads) in an electric circuit.
Closed Circuit − A circuit which is uninterrupted from the current source
and back to the current source.
Cold-Cranking Rating − A battery rating based on the amperes of
current that a battery can supply for 30 seconds at -18°C, with no battery
cell falling below 1.2 volts.
Collector − The area of a transistor which collects emitted electrons and
then passes them on through a conductor completing a circuit.
Colour Coding − The use of coloured insulation on wire to identify an
electrical circuit.
Commutator − That part of a starter motor where current is sent to the
rotating coils in the armature. It is the rotating connector between the
armature windings and the brushes. It consists of copper bars at one end
of the starter motor armature electrically insulated from the shaft and
insulated from each other by mica.
Compound Motor − A motor that has both series and shunt field
windings. Often used as a starter motor.
Computer Control − Control of any automotive system using solid state
devices and operating with a pre-programmed set of commands
(program), sensors to monitor various engine conditions (input), and
signals set to affect the function of some component (output). Also holds
commands in memory for later use.
Condenser − Electrical component used to store and release a current
through a secondary circuit. Can be used to protect a circuit against
surges in current, store and release a high voltage, or smooth out current
fluctuations. Also called a capacitor.
Conductivity − Measure of how easily an electrical component conducts
Conductor − Any material that allows electric current or heat to flow.
Current flows easily through a conductor because there are many free
Constant Voltage Charging − Method of charging battery in which a
constant voltage is applied and the current decreases as the battery
approaches the charged condition.
Continuity − Continuous, unbroken. Used to describe a working electrical
circuit or component that is not open.
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Control Circuit Resistance Test − Test used to determine if there is
high resistance in the control circuit that will reduce current flow through
the starter solenoid or relay windings and cause improper operation of the
starter circuit.
Conventional Theory − The current flow theory which says electricity
flows from positive to negative. Also called the positive current flow
Copper − A metal used for electrical conductors because it has less
resistance than most other metals.
Counter-electromotive Force − An induced voltage that opposes the
source voltage and any change (increase or decrease) in the charging
current. Abbreviated: CEMF.
Cranking − The act of engaging the starter by turning the ignition switch
to make the engine turn over.
Cranking Circuit − Motor feed and ground circuits required to supply
heavy current to the cranking or starter motor.
Cranking Circuit Resistance Test − Test used to determine if there is
excessive electrical resistance in the cranking circuit preventing full power
from reaching the starter motor.
Current − Flow of electrons through a circuit, measured in amperes.
Cut-out Relay − A relay that keeps the battery from discharging when the
engine is off or idling. It acts as a circuit breaker to open the circuit
between the battery and alternator.
Cycle − Any series of events repeating continuously. In electrical system
the flow of current alternates first in one direction and then in the opposite
Cycling − Battery electrochemical action. One complete cycle is the
operation from fully charged to discharged and back to fully charged.
Defective Device − A type of circuit malfunction in which a component of
electrical circuit does not work as it should. This could be a worn-out
battery, corroded switch, burned-out lamp bulb, or broken connector.
Delta-Type Winding − An alternator stator design in which the three
windings of a 3−phase alternator are connected end-to-end. The
beginning of one winding is attached to the end of another winding. Used
in alternators that must give high-amperage output.
Dielectric − The insulating material between the two conductive plates of
a capacitor.
Digital − Method of sending information through an electrical circuit by
switching the current on or off.
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Digital Computer − A computer that uses numbers to perform logical and
numerical calculations, usually in a binary (two digits) numbering system.
Faster and superior performance to an analogue computer.
Digital Readout − A display of numbers or a combination of numbers.
Diode − A semiconductor device made of P-material and N-material
bonded at a junction. It permits current to flow in one direction only, and is
used in rectification (changing alternating current to direct current).
Diode Trio − Six diodes, arranged in pairs front to back, each at the end
of a stator winding in an alternator. Used to rectify both phases of an
alternating current cycle to direct current.
Direct Current (DC) − A steady flow of current moving continuously in
one direction along a conductor from a point of high potential to a point of
lower potential.
Drive Belt − A flexible belt connecting the fan and the alternator, causing
both to turn through a pulley system at the end of the crankshaft.
Dry Cell − Voltage source consisting of three elements: a zinc cylinder, a
paste of electrolyte, and a carbon rod or electrode.
Eddy Current − Currents in armatures, pole pieces, and magnetic cores
induced by changing electromotive force. It is wasted energy and creates
Electrical Balance − An atom or an object in which positive and negative
charges are equal.
Electrical Charge − Property of electrons and protons that give a
substance its electrical characteristics. A deficiency of electrons in the
outer ring of atoms of a substance will give it a positive charge. An excess
will give the substance a negative charge.
Electrical Symbols − Simple drawings used to represent different parts
of an electrical circuit.
Electrical System − Parts of the vehicle that crank the engine for
starting, furnish high voltage sparks in the cylinders, operate lights and
accessories, and charge the battery. Electrical systems of a diesel include
circuits to operate the glow plug system.
Electricity − The controlled movement of electrons in a conductor.
Electrochemical Device − A device that operates on both electrical and
chemical principles (a lead-acid storage battery, for example).
Electrochemistry − In a battery, voltage caused by the chemical action
of two dissimilar materials in the presence of a conductive chemical
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Electrolyte − A solution of sulfuric acid and water used in a storage
battery that through chemical reaction produces electric potential.
Electromagnet − Coil of current-carrying wire usually wound around a
soft iron core that becomes magnetized when current passes through the
wire and demagnetized when the current stops.
Electromagnetic Field − The invisible field of force which surrounds a
charged conductor or coil.
Electromagnetic Induction − The creation of a voltage within a
conductor when relative motion exists between the conductor and a
magnetic field.
Electron − Those parts of an atom which are negatively charged and
orbit around the nucleus of the atom.
Electron Flow Theory − Belief that current flow consists of electrons
flowing from a point with a high potential of free electrons (negative) to a
point with fewer electrons (positive).
Electronic − Any system using integrated circuits or semiconductors to
control the flow of current. As opposed to electrical that describes
systems in which there are no solid state components and devices are
controlled by current applied to such components as motors, solenoids,
and relays.
Electron Theory − States that all matter is made up of atoms which are
made up of a nucleus and orbiting electrons. The ―free" electrons can
move from one atom to another, producing electricity.
Electrostatic Field − The area around an electrically charged body
resulting from the difference in voltage between two points or surfaces.
Element − A substance that cannot be further divided into a simpler
substance. In a battery, a group of positive and negative plates,
separated by insulators that make up each cell.
Emitter − Region in a transistor that emits (NPN) or collects (PNP) large
number of electrons as a small number of electrons are taken from or
added to the base.
Energize − To put energy into. The iron core of an electromagnet is
energized by passing current through the coil.
Equivalent Resistance − The total resistance of a parallel circuit. The
single mathematical equivalent of all the parallel resistances.
Farad − The unit of measurement of capacitance.
Feedback System − Electronic system in which sensors monitor the
output of various automotive systems and provide input to control the
Reproduced by Speciss College with permission from Kevin Sullivan -
operation of the system and change the output. It is a self-correcting
Feed Circuit − Line supplying alt the branch circuits with the main supply
of current. Generally used to refer to the hot (not grounded) feed from the
battery to the electrical components of a vehicle.
Field Coil − Winding of current-carrying conductors used in a starter
motor to produce a magnetic field.
Field Magnet − A magnet for producing and maintaining a magnetic field
especially in an alternator or electric motor.
Field Relay − A magnetic switch used to open and close the alternator
field circuit, or in a charging circuit with a warning lamp, to control the
lamp circuit.
Field Strength − The density of magnitude of the magnet lines of force.
The denser the magnetic field, the more lines of force will extend from
pole to pole in the magnet and the stronger the field will be.
Field Windings − Insulated wire wrapped around an iron or steel core.
When current flows through the windings, a strong magnetic field is
Filament − A resistance in an electric light bulb which heats up and
glows, producing light, when an adequate current (bombardment by
electrons) is sent through it.
Flux − The lines of magnetic force flowing in a magnetic field.
Flux Density − The number of flux lines in a magnetic field area. The
more flux lines in a unit of area the stronger the magnetic field at that
Forward Bias − The application of a voltage to produce current flow
across the junction of a semiconductor.
Free Electron − An electron in the outer orbit of an atom, not strongly
attracted to the nucleus, and can therefore be easily forced out of its orbit
into orbit around the nucleus of another atom.
Frequency − Number of times every second an alternating current goes
through a complete cycle. Now measured in units of hertz (Hz) but
previously measured in cycles per second (cps).
Full-Wave Rectification − A process by which all of an A.C. voltage
wave is rectified and allowed to flow as D.C.
Fuse − A device containing a soft piece of metal which melts and opens,
or breaks, the circuit when it is overloaded. Similar in function to a ―circuit
breaker," but must be replaced after circuit problem is corrected.
Fusible Link − A short piece of wire soldered into a heavy feed circuit,
designed to melt when an overload occurs. Performs the same function
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as a fuse or circuit breaker. Like the fuse, it must be replaced after the
circuit problem is corrected.
Gassing − Escape from a battery of highly explosive hydrogen gas
formed during charging.
Generator − An apparatus that produces an electric current through
magnetism. Its A.C. (Alternating Current) output is internally changed to
D.C. (Direct Current) through the commutator. The alternator, a type of
generator, changes its A.C. output to D.C. through the use of diodes.
Glow Plug − A resistance heater, shaped somewhat like a spark plug,
heated by low voltage current. Used to heat compressed air in a diesel
engine until the heat of combustion reaches the temperature to cause
self-ignition without assistance.
Grid − Frame of a storage battery plate having spaces in which the active
material in paste form is pressed.
Ground − The return path for current flow in a circuit. In automotive use,
the circuit ground path is usually the vehicle frame and metal body parts.
Ground Cable − The battery cable that provides a ground connection
from the vehicle chassis to the battery.
Grounded Circuit (Unintentional) − A type of circuit malfunction in which
the current in the circuit is accidentally shunted, or diverted to ground.
Usually, this condition bypasses a load. If a load is bypassed, it reduces
the resistance of the circuit and can cause wiring to overheat, fuses to
blow, etc.
Ground-Seeking − A test method using a 12−volt test light where one
lead is connected to a known power source and the other lead is touched
to various points of a circuit to seek a point where the circuit is grounded.
Ground Terminal − The terminal of the battery connected to the metal
frame and chassis of the vehicle for the return path of current flow back to
the battery, usually to the negative terminal.
H2O − Chemical symbol for water.
H2S04 − Chemical symbol for sulfuric acid.
Half-Wave Rectification − A process by which only one-half of an A.C.
voltage wave is rectified and allowed to flow as D.C.
Heat Sink − Device to absorb heat from one medium by transferring it to
another. Diodes in alternators are mounted on heat sinks to prevent the
diodes from overheating,
High Rate Discharge Test − Battery test in which the battery is
discharged at a high rate of current while cell voltages are checked.
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High Resistance − A type of circuit malfunction in which a loose, dirty or
corroded connection limits current flow below specifications. The result
can be dimmed lamps, flickering lamps, or even inoperative devices.
Hold-In Winding − The coil of small-diameter wire in a solenoid that
creates a magnetic field to hold the solenoid plunger in position inside the
Hole − The space in a valence ring where another electron could fit.
Hydrogen − (H) Colourless, odourless, highly flammable gas. Simplest
and lightest element having only one electron orbiting around the nucleus.
Hydrometer − Device used to measure the weight of a liquid, or its
specific gravity. Used to measure the acid content of electrolyte in
batteries or the ethylene-glycol content of coolant.
Ignition − Action of the spark in starting the burning of the compressed
air/fuel mixture in the combustion chamber.
Ignition Coil − An induction coil used to produce a high voltage current to
jump the gap in a spark plug and ignite the air/fuel mixture in the
combustion chamber. A small voltage turned on and off in the primary
windings induces a much larger voltage as the output from the secondary
Ignition Resistor − A resistance in the primary ignition circuit to reduce
the amount of battery voltage available at the coil.
Ignition Switch − Switch used to open and close the circuit to the
primary ignition coil. Also used to open and close accessory circuit on the
Ignition System − System to furnish high voltage sparks to the cylinders
to ignite the compressed air/fuel mixture at the right time. Consists of the
battery, ignition coil, distributor, ignition switch, wiring and spark plugs.
Indicator − Device used to make some condition known by use of a light
or gauge.
Indicator Light − An illuminated warning or indicator to the driver of a
vehicle of some condition, such as when the alternator is not supplying
current or when the coolant temperature is close to overheating.
Induced Voltage − The voltage which appears in a conductor when
relative motion exists between it and magnetic flux lines.
Induction − Producing a voltage in one conductor or coil by moving the
conductor or coil through a magnetic field or by moving the magnetic field
past the conductor or coil.
Infinite Reading − A reading (∞) on an ohmmeter that indicates an open
circuit − broken wire, defective component.
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Infinite Resistance − Very high resistance, a value higher than can be
conceived. No current can move through. Usually, circuit is broken with
no complete path for current flow.
Initial Charge Rate − The current a battery will accept at the start of
charging. Charging current decreases as charging progresses.
Input − Generally used to refer to the data or instructions given or fed into
a micro-computer.
Insulated Cable − The battery cable that conducts battery current to the
automotive electrical system.
Insulators − Materials that will not conduct electron flow because of their
many bound electrons.
Integrated Circuit − (IC) An electronic circuit containing transistors,
diodes, resistors, and capacitors along with electrical conductors
processed and contained entirely within a single chip of silicon.
Ion − An atom which has become unbalanced by losing or gaining an
electron. It can be positively or negatively charged.
Ionize − To break up molecules into two or more oppositely charged ions.
The air gap between the spark plug electrodes is ionized when the air/fuel
mixture is changed from a non-conductor to a conductor.
Jump Starting − Using a booster battery to start a vehicle in which the
battery does not have sufficient charge to start the vehicle itself.
Jumper Wire − A test device or tool used by technicians to create a
temporary bypass for current in a circuit. A jumper wire may be used to
ground a circuit, to bridge a broken wire or switch, or to complete a circuit
for test purposes.
K − Prefix used in the metric system of measurement to mean 1000 times
the stated value. Abbreviation for kilo.
Kilowatt − Unit of power in the metric system. One kilowatt is equal to
about 1.341 horsepower. Also used to describe 1000 watts of electrical
Knock Sensor − An acoustical device used to sense engine vibrations
caused by self-ignition, or knock, and signal an electronic control module
to adjust spark timing and reduce detonation.
Lead-Acid Battery − A common automotive battery in which the active
materials are lead, lead peroxide, and a solution of sulfuric acid and
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Lead Sulphate − Hard, insoluble layer that slowly forms on the plates of
a discharged battery and can only be reduced by slow charging. Caused
by the chemical reaction of the acid in the electrolyte acting on the lead
peroxide and sponge lead of the active material in the plates.
Leakage Current − Unwanted current flowing through a semiconductor
or capacitor.
Left-Hand Rule − A method of determining the direction of the magnetic
flux lines surrounding a current-carrying conductor when the electron
theory of current flow is used (− to +). If the conductor is grasped with the
left hand so the thumb points in the direction of current flow, the fingers
will point in the direction of magnetic flux.
Light Emitting Diode (LED) − A semiconductor diode designed so light
is emitted when forward current is applied to the diode.
Light-Load Test − A test applied to storage batteries during which the
voltage is measured while the battery is subjected to a light load, such as
the car headlights.
Lines of Force − Imaginary lines representing the direction of magnetism
around a conductor or from the end of a magnet.
Liquid Crystal Display (LCD) − Uses a polarized light principle and a
liquid crystal to display numbers and characters.
Loss of Power − A type of circuit malfunction in which the voltage source
for the circuit or device is lost. This could be a worn-out or defective
battery or an OPEN CIRCUIT on the battery side of the electrical load.
Magnet − Any body with the property of attracting iron and steel.
Temporary magnets are made by surrounding a soft iron core with a
strong electromagnetic field. Permanent magnets are made with steel.
Magnetic Circuit − Paths taken by lines of force in going from one end of
the magnet to the other.
Magnetic Field − The area near a magnet where the property of
magnetism can be detected. Also the flow of magnetic force between
opposite poles of a magnet.
Magnetic Flux − The invisible, directional lines of force which make up a
magnetic field.
Magnetic Flux Density − Strength of the magnetic lines of force. The
denser the magnetic flux, the more lines of force will extend from pole to
pole in the magnet.
Magnetic Induction − Producing magnetism in a magnetic body by
bringing it near a magnetic field.
Magnetic Pole − Point where the lines of force enter and leave a magnet.
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Magnetic Saturation − The condition when a magnetic field reaches full
strength and maximum flux density.
Magnetism − A form of energy caused by the alignment of atoms within
certain materials. The ability of a metal to attract iron.
Maintenance-Free Battery − Battery that does not require the addition of
water during its normal service Grids in maintenance-free batteries are
made of metals other than antimony to produce less gassing and
therefore, less chance of pushing electrolyte from the battery.
Matter − The substance of which a physical object is composed.
Memory − Part of a microprocessor or microcomputer in which
instructions or data are stored as electrical impulses.
Micro − Prefix of measurement meaning one millionth of a part.
Microprocessor − Set of integrated circuits that can be programmed with
stored instructions to perform given functions. A computer in the lowest
range of size and speed containing a central processing unit (CPU),
instructions stored in a read only memory (ROM), and a random access
memory (RAM) for receiving data and instructions. Also called a
Milli − Prefix of measurement meaning one thousandth of a part.
Millisecond − Unit of measurement for time, meaning one thousandth of a
Module − A self-contained, sealed unit that houses the solid-state circuits
needed to control certain electrical or mechanical functions.
Molecule − Two or more atoms joined together to form an element or a
chemical, compound.
Motor − An electromagnetic device used to convert electrical energy into
mechanical energy.
Nanosecond − One billionth-of a second. A unit of measurement usually
referring to the speed the circuit in a microcomputer can work. Electricity,
travelling at the speed of light, will travel about 30 centimetre in one
nanosecond. In comparison the same electricity will travel about 300
meter in one microsecond (millionth of a second).
Negative Polarity − Also called ground polarity. A correct polarity of the
ignition coil connections. Coil voltage is delivered to the spark plugs so
that the centre electrode of the plug is negatively charged and the
grounded electrode is positively charged.
Negative Pole − The point to which the electrons forming an electric
current return from a circuit. Also referred to as the south pole in
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Negative Temperature Coefficient − The property of any substance in
which the electrical resistance increases as the temperature of the
substance decreases.
Negative Terminal − The battery terminal closest to the negative
potential in the battery.
Neutron − A particle in an atom that has no charge and is electrically
N-Material − A semiconductor material that has excess free electrons
because of the type of impurity added. It has a negative charge and will
repel additional electrons.
No-Load Test − A cranking-motor test in which the cranking motor is
operated without load; the current draw and armature speed at the
specified voltage are noted.
North Pole − The area of a magnet from which the lines of force are said
to leave the magnet. The end of a magnet that will point toward the north
if freely suspended.
NPN Transistor − Transistor with two layers of N-type material separated
by a layer of P-type material. Base circuit must be positive relative to the
emitter for current to flow through the collector circuit.
N-Type Material − Semiconductor material with an excess of free
electrons because of some impurity added. It has a negative charge and
will repel additional electrons.
Nucleus − The centre core of an atom that contains the protons and
Ohm − The standard unit for measuring the resistance to current flow.
One ohm of resistance will limit current flow to one ampere when one volt
of pressure is applied.
Ohm’s Law − The mathematical relationship between voltage, current,
and resistance. The pressure of one volt applied to one ohm of resistance
will cause one ampere of current to flow. Amps equal volts divided by
ohms (I = E/R). Volts equal amps times ohms (E = I X R). Ohms equal
volts divided by amps (R = E/I).
Ohmmeter − An electrical meter used to measure the resistance to
current flow in a circuit or working load. It reads ohms of electrical
resistance. The ohmmeter can only be connected across a circuit or
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device with the power removed. This meter has its own battery and will be
damaged if connected to a circuit that has power applied.
Open Circuit − A type of circuit in which there is an incomplete path for
current flow. The open circuit may be caused deliberately, by a switch
that is in the OFF position, or it may be caused by a break in the
conductor. An open circuit can occur on either side of the load; however,
an open circuit in the ground side of the circuit is usually referred to as a
Open-Circuit Voltage − The voltage across the battery terminals with no
load applied.
Oscilloscope − An electric instrument producing, on a screen, a visual
display or trace of voltage changes in an electrical circuit.
Overcharging − Continued charging of a storage battery after it has
reached the fully charged state. This damages the battery and shortens
its life.
Overload − Carrying a greater load than the device, machine, or electric
circuit is designed to carry.
Parallel Circuit − A circuit in which the components are arranged so that
there is a separate current path to each component. In a parallel circuit,
the components are connected positive-to-positive and negative-tonegative.
Permanent Magnet − Piece of metal that holds its magnetism without the
use of continuing electric current to create a magnetic field.
Permeability − A measure of the ease or difficulty with which materials
can be penetrated by magnetic flux lines. Iron is more permeable than air.
Photo-electricity − Voltage caused by the energy of light as it strikes
certain materials.
Piezoelectricity − Voltage caused by physical pressure applied to the
faces of certain crystals.
Plate − Material in a storage battery that reacts with the acid in electrolyte
to produce a voltage for current flow. Usually made of a soft porous lead
compound supported by a harder metal grid. If the plate is sponge lead it
has a positive charge; if it is made of lead peroxides, it has a negative
Plate Group − The positive and negative plates in one cell of a battery,
connected together to produce approximately 2.2 volts.
PN Junction − Dividing line in a semiconductor between P-type material
and N-type material. Electrons can flow from N to P but not from P to N.
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PNP Transistor − Transistor with two layers of P-type material separated
by a layer of N-type material. Base circuit must be negative relative to the
emitter for current to flow through the collector circuit.
Polarity − The quality or condition in a body that has opposite properties
or directions. A collective term applied to the positive (+)and negative (−)
ends of a magnet or electrical component such as a battery or coil.
Polarize − The process of establishing positive and negative polarity
across alternator fields and thus determining the direction of current flow.
Polarizing − A method of maintaining the electrical and magnetic polarity
of the pole shoes and field in an alternator.
Poles − Positive and negative terminals of a cell or battery. Also, the
ends of a magnet (north and south).
Pole Shoes − Magnetic iron cores, or poles, that provide the magnetic
field in an alternator or motor and strengthen the electromagnetic field of
the field windings.
Positive Charge − The electrical characteristics of a substance with a
deficiency of electrons in the outer ring of its atoms.
Positive Plate − The dioxide of lead plate in a lead-acid storage battery.
Positive Polarity − Also called reverse polarity. An incorrect polarity of
the ignition coil connections. Coil voltage is delivered to the spark plug so
that the centre electrode of the plug is positively charged and the
grounded electrode is negatively charged.
Positive Pole − The point from which the electrons forming an electric
current enter a circuit as defined by the • Conventional Theory." Also
referred to as the north pole in magnetism.
Positive Temperature Coefficient (PTC) − Resistor or heating element
in which the resistance increases with temperature, heat created by
current flowing through it. Eventually the resistance will get so high that it
will oppose all current flow. Then, the resistor or heating element will cool
down until current can begin to flow again, increasing the temperature.
Positive Terminal − The battery terminal from which electrons flow in a
complete electrical circuit. Generally the side of the circuit not connected
to ground.
Potential − The pressure (voltage) existing between two points available
to force electrons through the circuit as current.
Potentiometer − Electrical component that can vary the amount of
resistance placed in a circuit by turning or sliding a contact on the
resistance wire windings.
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Power − Rate at which work is done. Common unit of measure for power
is horsepower. Power is also measured by kilowatt (kW). About threefourths of a kilowatt equal one horsepower.
Power Feed Circuit − Wires that carry current from the positive terminal
of the battery to the electrical components of the vehicle.
Power-Seeking − A test method using a 12−volt test light where one lead
is connected to a known ground and the other lead is touched to various
points of a circuit to seek a point where power is present.
Power Supply − Sources of voltage in a circuit.
Pre-glow − The time it takes a glow plug to reach a temperature at which
it will cause ignition of the mixture in the cylinder.
Primary Winding − Winding of relatively heavy wire in an ignition coil that
receives current from the battery to create a magnetic field and induce a
voltage in the secondary windings of the coil.
Primary Wiring − The low-voltage wiring in an automobile electrical
Printed Circuit − An electrical circuit made by etching a conductive
material on an insulated board into a pattern to provide current paths
between components mounted on the board.
Programmable Read-Only Memory (PROM) − Part of a microprocessor
or computer in which instructions or data are semi-permanently located.
PROM data can be changed (like a RAM) but are not volatile memory
(they do not erase when the power is turned off but are permanently
configured as part of the electronic circuit).
Proton − One of the positive-charged particles in the nucleus of an atom.
P-Type Material − Semiconductor material with holes as part of its basic
structure. It has a positive charge and will attract additional electrons.
Pull-In Winding − The coil of large-diameter wire in a solenoid that
creates a magnetic field to pull the solenoid plunger into the coil.
Quick Charger − Battery charger used to produce a high charging
current to boost the charge of a battery in a short time.
Random Access Memory (RAM) − Part of a microprocessor or
computer into which information can be written and from which
information can be read.
Reactance − Property of an electrical device or conductor to impede
change in current passing through it or voltage exerted on it.
Read-Only Memory (ROM) − Part of a microprocessor or computer
where information and instructions are permanently integrated Into the
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circuits and can only be read by the processor. Usually used to store the
program or instructions for the processing unit to act on.
Rectifier − Device used to change alternating current to direct current.
Regulator − Device in the charging system used to control alternator
output to prevent excessive voltage from being fed to the battery or to the
electrical components in a vehicle.
Relay − An electromagnetic switch. A relay uses a small amount of
current flow to control the flow of a larger amount of current through a
separate circuit.
Reluctance − The tendency of some materials to resist penetration by
magnetic flux lines.
Required Voltage − Voltage needed to fire a spark plug.
Reserve Capacity Rating − A battery rating based on the number of
minutes a battery at 26°C can supply 25 amperes, with no battery cell
falling below 1.75 volts.
Resistance − The opposition to the free flow of an electric current,
measured in ohms.
Resistor − A device made of carbon or wire that presents a resistance to
current flow. Any device in a circuit that produces work, loads the circuit,
and causes a voltage drop acts as a resistor.
Resistor Plug − A spark plug with a resistor in the centre electrode to
reduce the inductive portion of the spark discharge. Used to minimize
radio and television interference caused by spark plugs.
Resistor Wire − Conductor of a given diameter and length that adds
resistance, usually a low value, to a circuit.
Reverse Bias − Polarity of voltage applied to the junctions of a diode or
transistor so normally no current will flow across the junction.
Reverse Breakdown Voltage − The reverse voltage beyond which a
diode cannot hold back reverse current.
Reverse Current − Amount of current flowing from cathode to anode
when a given reverse voltage is imposed on a diode or transistor.
Rheostat − A resistor for regulating a current by means of variable
Right-Hand Rule − A method of determining the direction of magnetic
flux lines surrounding a current-carrying conductor, when the
conventional theory of current flow is used ( + to −). If the conductor is
grasped with the right hand so the thumb points in the direction of
conventional current flow, the fingers will point in the direction of magnetic
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Rotor − Revolving part of a device, such as an alternator rotor, distributor
rotor, or rotary combustion engine rotor.
Schematic Diagram − A drawing of a circuit, or any part of a circuit, that
shows how it works.
Secondary Circuit − High voltage circuit of the ignition system consisting
of the coil, rotor, distributor cap, spark plug cables, and spark plugs.
Secondary Winding − The coil winding made of many turns of a fine
wire, in which voltage is induced by the rise and collapse of the magnetic
field of the primary winding.
“See-Saw" Rule − An easy way to remember and use Ohm‘s Law in your
work. If voltage stays the same, but current is above specs, resistance
must be down − possibly a short circuit. If voltage stays the same, but
current is below specs, resistance must be up − possibly a bad
Self Discharge − Chemical activity in a battery causing the battery to
discharge even though it is not supplying a circuit or component with
Self-Induced Voltage − Voltage created in a conductor by the magnetic
lines of a current through that same conductor.
Self-Powered Test Light − Used to check for continuity in a circuit or
load device. Test unit uses a low voltage battery (1.5 volts) and bulb, and
test leads.
Semiconductor − Popular name associated with almost any solid state
circuit or component. Materials with four electrons in the outer ring of the
atom which show the properties of a conductor or a non-conductor under
different conditions.
Sending Unit − Sensor in the engine at a convenient point of an oil
gallery or coolant passage to send a signal to a gauge or light indicating
the pressure or temperature of the oil or coolant.
Series Circuit − A circuit in which the parts are connected end to end,
positive pole to negative pole, so that only one path is available for all
current flow.
Series Motor − A motor that has only one path for current flow through
the field and armature windings. Commonly used for starter motors.
Series-Parallel Circuit − The connection of several loads in a circuit in
such a way that current must flow through some loads, but can flow to
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one or more other loads without affecting the rest of the circuit. A seriesparallel circuit is simply a circuit containing elements of both a series
circuit and a parallel circuit.
Short Circuit − A type of circuit malfunction in which two or more wires
touch each other accidentally, in such a way that the circuit(s) are
completed wrong. A short circuit between two different circuits
interconnects the two in such a way that if either circuit is electrically
energized, both will function.
Shunt − Parallel. An electrical connection or branch circuit in parallel with
another branch circuit or connection.
Shunt Motor − A motor that has its field windings wired in parallel with its
armature. Not used as a starter motor, but often used to power vehicle
Silicon − Element commonly used in making semiconductor material.
Sine Wave Voltage − The constant charge, first to a positive peak and
then to a negative peak, of an induced alternating voltage in a conductor.
Single-Phase Current − Alternating current caused by a single-phase
Single-Phase Voltage − The full wave voltage induced within one
conductor by one revolution of an alternator rotor.
Slip Rings − Parts of an alternator forming a rotating connection between
the field coil windings and the brushes.
Solenoid – Electromechanical device used to produce mechanical
movement by drawing a plunger into a coil when current is applied to the
coil. Used to control a valve, switch contacts, or control other moving
Solenoid-Actuated Starter − A starter that uses a solenoid both to
control current flow in the starter circuit and to engage the starter motor
with the engine flywheel.
Solid State − Electronic components consisting mainly of silicon chips
and similar conductive materials.
Solid State Regulator − Voltage regulator made from semiconductor
components mounted in the alternator.
Solid Wire − A conductor made of one piece instead of being made from
a number of smaller wires.
South Pole − Area of a magnet where the magnetic tines of force
converge and enter the magnet.
Spark Plug − Device used to provide the heat or flame to ignite
compressed air/fuel mixture in the combustion chamber. Consists of two
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accurately spaced electrodes and a threaded outer shell to screw into the
cylinder head.
Specific Gravity − Weight of a substance compared to the weight of
water. Any substance with a specific gravity of less than 1.00 is lighter
than water; more than 1.00 is heavier than water. The amount of another
substance (such as battery acid or antifreeze) in water can be determined
by measuring the specific gravity of the mixture.
Sponge Lead − Porous lead used as the active material of the negative
plate of a lead-acid storage battery.
Starter Motor − Electric motor used to crank the engine for starting.
Starter Motor Load Test − Test used to identify internal problems in the
starter motor.
Starter No-Load Test − Test used to uncover such faults as open or
shorted windings, rubbing armature, and bent armature shaft.
Starter Relay − Electrical switch on the starter motor that uses a smaller
current from the ignition circuit to control a larger current from the battery
to the starter motor.
Starter Solenoid − An electrically operated plunger mechanism on the
starter motor used to engage the starter pinion gear with the ring gear on
the flywheel. Also used to control the current to the starter motor.
Starting Bypass − A parallel branch circuit that bypasses the primary
ballast resistor during cranking.
Starting Control Circuit Test − Test used to determine whether failure to
crank is due to open circuits, defective wiring, or poor connections
causing excessive resistance in the starter control circuit.
Starting Safety Switch − A neutral start switch. It keeps the starting
system from operating when a car‘s transmission is in gear.
Starting System − Components in the electrical system used to crank
the engine until it can begin running on its own.
State-of-Charge − A measurement of a battery‘s internal condition in
relation to a fully charged unit, usually expressed as a percentage of full
Static Electricity − Voltage resulting from the transfer of electrons from
the surface of one material to the surface of another material. The
electrons are • static," meaning at rest.
Stator − In an alternator, it is the part which contains the conductors
within which the field rotates.
Storage Battery − Device used to change chemical energy into electrical
energy. Part of the electrical system acting as a reservoir for electrical
energy, storing it in a chemical form.
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Stranded Wires − Wires or cables made of a number of smaller wires
twisted or braided together.
Sulfation − The crystallization of lead sulphate on the plates of a
constantly discharged battery.
Sulfuric Acid − Highly corrosive chemical compound used in a diluted
form as the electrolyte in storage batteries.
Switch A device used for opening, closing, or changing the connections
in an electric circuit.
Symmetrical − The same on either side of centre. In a symmetrical highbeam headlamp, the light beam is spread the same distance to either
side of centre.
System Diagram − A drawing that shows all of the different circuit
diagrams in a complete electrical system.
Temperature Correction − The amount that must be added to or
deducted from a reading taken at one temperature to make it comparable
with the same reading taken at a standard temperature.
Terminal − A device attached to the end of a wire or to an apparatus for
convenience in making electrical connections.
Test Lamp − A 12−volt lamp with leads (wires) attached so that the lamp
can be temporarily inserted in an electrical circuit, either in series or in
parallel with it. It is used to confirm that voltage is available to a specific
point in a circuit.
Thermistor (Thermal Resistor) − A resistor especially built to reduce its
resistance as the temperature increases.
Thermoelectricity − Voltage resulting from an unequal transfer of
electrons from one metal to another, when one of the metals is heated.
Three Phase Current − Combination of three alternating current cycles,
each starting one−third of a cycle apart so each of the cycles in the
resulting combined wave is 120 degrees out of phase from the others.
Provides a smoother direct current flow when rectified because voltages
of each alternating cycle are not allowed to decay completely before the
next cycle begins to rise.
Thyristor − A silicon-controlled rectifier (SCR) that normally blocks all
current flow. A slight voltage applied to one layer of its semiconductor
structure will allow current flow in one direction while blocking current flow
in the other direction.
Transducer − A device that changes one form of energy into another. In
an ignition system, it may sense a mechanical movement and change it to
an electrical signal.
Reproduced by Speciss College with permission from Kevin Sullivan -
Transformer − Device used to change alternating current from one
voltage to another. Consists of two coils, one with more windings than the
other, that induce voltage in one coil when current flows to the other. Can
increase or decrease applied voltage.
Transistor − A semiconductor device with three connections. A small
current at the control junction between semiconductor materials is used to
control a larger current between two rectifying junctions.
Trickle Charge − A low rate of charge given to a storage battery over a
long period of time.
Twenty Hour Rate − Battery rating measuring the amount of current a
battery can deliver for 20 hours with an electrolyte temperature of 27°C
before the cell voltage drops to 1.75 volts.
V − Abbreviation for volt, a unit of measurement for electrical potential.
Valence Ring − The outermost electron shell of an atom.
Volt − The unit for measuring current pressure in a circuit. One volt of
pressure causes one ampere of current to flow against one ohm of
Voltage − The electromotive force that causes current flow. The potential
difference in electrical force between two points when one is negatively
charged and the other is positively charged.
Voltage Drop − The difference in potential (voltage) between one point in
a circuit and another; typically the voltage difference from one side of a
component to the other.
Voltage Leak − The loss of charge in a capacitor because of the
imperfect insulating characteristics of the dielectric, allowing voltage to
―leak" across, neutralizing the electrical charge,
Voltage Loss (Also Called Voltage Drop) − Reduction in voltage across
an electrical device or circuit because of the resistance to current flow of
that device or circuit.
Voltage Regulator − A relay that limits an alternator‘s voltage output.
Voltmeter − An electrical meter used to measure the difference in voltage
between two points in a circuit. It reads volts of electrical pressure. The
voltmeter must be connected across the load or circuit _ red lead on the
battery side of the circuit, black lead on the ground side of the circuit.
W − Abbreviation for watt, a unit of measurement for power.
Reproduced by Speciss College with permission from Kevin Sullivan -
Warning Light − Light that illuminates to alert the driver to some
condition in the vehicle such as battery charging rate, high coolant
temperature, or low oil pressure,
Watt − The unit of measurement for electric power. One way to measure
the rate of doing work. Watts equal volts times amperes.
Watts Rating − A method of rating the available cranking power of a
battery. The rating can be found by multiplying the current available from
the battery by the battery voltage at -18°C.
Wire Gauge − Wire size numbers based on the cross section area of the
conductor. Larger wires have lower gauge numbers.
Wiring Diagram − A schematic. The representation of an electrical circuit
by a drawing. A wiring diagram may contain electrical symbols for various
loads and components.
Wiring Harness − A bundle of wires enclosed in a plastic cover and
routed to various areas of the vehicle. Most harnesses end in plug-in
connectors. Harnesses are also called looms.
Y-Type Winding − An alternator design in which one end of three
windings is connected at a neutral junction.
Zener Diode − A semiconductor made so it will allow reverse current flow
without damage at a voltage above a specific value
Reproduced by Speciss College with permission from Kevin Sullivan -
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