Learn how to convert your vehicle from 6 volts to 12 volts
Hi, Below are the step by step 6 volt to 12 volt report you requested from us.
Before we get into how to convert your car or truck from 6
volts to 12 volts, let's discuss some basic electricity as this will help in the understanding
of your vehicles electrical system.
You can think of electricity like water.
The battery acts like a reservoir and provides the
pressure and volume,
the wiring is the hose and resistance is the nozzle
that does the work.
How Electricity Works. When you double the
voltage or increase the capacity of the water tank
you decrease the pressure or amperage needed
to drive an electrical device. In the case of
changing a 6 volt system to 12 volts, you are
doubling the voltage thus decreasing the
amperage in half. This is why you can use the
same wiring and mechanical switches in a 12 volt system as you have in your 6 volt
This means you don't need to rewire your vehicle when converting to 12
volts. This of course, assumes your wiring is in good shape and not a hazard.
Electrical terms to help:
Direct Current
Alternating Current
Series Wiring: Like a sting of old Christmas tree lights, one
goes out they all go out.
Parallel : Wired similar to your home lighting system each light is
powered individually.
Volts :
Pressure of electricity
Volume of electricity (this is what does the work)
Watts :
Amount of electricity used or needed to power a device
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Learn how to convert your vehicle from 6 volts to 12 volts
Device that controls the volume of electricity, acts
like a hose nozzle
Defines the direction current flows
Capacitor: Device that stores electricity for short periods of
Diode: allows current to flow in one direction only.
Those that are interested below is Ohms
Ohm's Law defines the relationships
between (P) power, (E) voltage,
(I) current, and resistance. One ohm is the
resistance value through which one volt will
maintain a current of one ampere.
Knowing this formula and applying your
high school algebra you will be able to
figure the various loads
and power required in your vehicle.
Now, lets talk about safety, your safety. You can become injured
working around electricity; you may not think 6 or 12 volts can hurt
you, but a 6 or 12 volt battery can pull lots of current if you get in
between the positive and negative and the situation are right.
You can get badly burned or even worse.
Anytime you work around your vehicle electrical
system always un-hook the battery terminals and be careful when removing the
terminals too.
Positive versus negative grounded electrical systems:
Ford, Dodge, Chrysler, Plymouth, Studebaker, Cadillac, Kaiser and some others wired
there earlier automobiles with the positive terminal of the battery to ground or frame and
the negative went to the starter solenoid and electrical system. Chevrolet and most GM
(except Cadillac) wired there vehicles with negative grounds.
After the late 50’s early 60’s most every manufacture went to
negative grounded electric systems and this is the standard today. Note modern solid
state electronics are based on negative grounded systems.
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When doing your conversion from to 12 volt you will want to
switch your systems to negative ground by changing the
terminals on the battery, the negative to the chassis and
or engine and the positive is going direct to the starter solenoid and or electrical system.
Remember all modern auto electrical systems are
negative ground systems and all solid state radios and other solid
state accessories are designed with negative ground systems. If you want to
plug in your smart phone or music player you will need a negative grounded system.
You will damage a solid state radio or most any solid state component if you run
positive ground unless you are running a converter which we will cover later.
For the positive ground vehicles going to negative ground, everything in your vehicle will
work as it does today. And I will remove the myth about starters turning backwards
when changing from pos to neg. ground as we get this question all the time.
When you change polarity your starter will NOT turn
You may ask yourself why this is as we all had these little
DC motors when we were
kids and to reverse the direction you reversed the wires on
the battery, correct?
The difference is, in those little electric motors, they have
permanent magnets motors and you indeed can change
direction the motor turns when polarity is reversed.
The starter in your vehicle does not uses permanent
magnets, instead it uses field coils to energize and create the magnetic force and these
types of motors are designed to turn in one direction only regardless of polarity.
(See image)
Your 6 volt starter uses a heavier gage wire in the field and armature windings than will
be found in a 12 volt starter and that is the reason most of the 6 volt starters will work on
12 volts.
Yes, the starter will turn faster (about 2X faster with 12 volts) and will start your engine
quickly when hot or cold.
If your 6 volt starter does not work now you can have rebuilt and convert to 12 volts.
If you have a Ford Flathead V8 there are new starter that are light weight and looks like
the original. Click this link to see
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Learn how to convert your vehicle from 6 volts to 12 volts
Lets get started. Start by disconnecting the 6 volt battery and
removing from the vehicle, remove the 6 volt voltage regulator
and generator. The wires from the generator to the regulator can either be removed
completely or kept and taped back in case the next person want to convert back to 6
volts. Some like to keep the regulator on the firewall and use purely as a connection
point for the wires connected to the Battery post of the regulator. Field and Armature
wires should be disconnected and taped back to the wire harness.
You have the option to either convert your generator to 12 volts or
install an alternator with built-in voltage regulator, will discuss both ways.
Staying with a generator and converting to 12 volts is a personal decision, if you want
the original look under the hood and can live with around 40 amp generator output then
this could be a good option for you.
If your vehicle will require more than about 40 amps then a modern alternator is a
better option. Most alternators come in 63, 90, 100 amp variety. 63 amps is plenty if you
will be running a stock vehicle, if you plan to install electric cooling fans or AC then 90 or
100 amps will be needed.
The disadvantage of a generator is the inability for the generator to produce
current at low engine speeds, you may need to be driving at 20 MPH or so before your
generator kicks in, this means at idle speed you are running off the battery and maybe
why your engine is hard to start after driving short distances.
The advantage of an alternator is the ability to generate higher
amperage output at a wide range of engine speeds.
The disadvantage if there is one, an alternator will not charge a dead
Because alternators unlike generators require a fully charged battery to
excite the field coils within the alternator. This is why you need to completely charge
your battery when installing an alternator.
The good news is, the battery will stay charged with an alternator at most all engine
speeds. (Will expand on this a little latter)
Modern alternators come in 1 or 3 wire configurations,
Let’s explain the difference between these alternators.
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The main difference is the type of internal regulator that is installed in the alternator.
1 wire alternators only have an output connection on the alternator and typically no
other connection points. Yes this is simple for sure, but you give up the ability to activate
a dash (no charge light) or sometimes referred to as an “Idiot light” charge and more
important for older engines is the ability to excite the alternator at low engine idle
speeds to keep your battery charged.
If you are familiar with generator cut off switches that turns the generator off at low
speeds, the alternator has a similar feature. Both have what is referred to as turn on
speeds. Alternators are set somewhere around 1200 to 1400 RPM. Generators turn on
at engine speeds that would equate to 15-20 miles per hour. The reason these cut out
and turn on switches exist is to take the generator or alternator out of the electrical
circuit when the vehicle is turned off.
What does all this mean?
Without getting into too much detail, older engines with generators were not designed
for alternators and the pulleys sizes are such that will only turn the generator so fast,
because if you turn a generator too fast it will overspeed, overheat and melt the solder
in the armature, this was referred to as “throwing the solder”.
Now install an alternator onto your older and generally slow idling engines the alternator
will not turn fast enough to reach the internal regulator turn on speed to charge your
battery. You can rev the engine up and the regulator will turn on, but there is no
guarantee the regulator will stay on when the
engine reaches idle speed again. You can
see this when older car headlights dim at a
stop light and brighten up when the engine
revs up.
Ideally you want your alternator to stay on all
the time to charge your battery similar to
your modern car and to achieve this, you
want to install a 3 wire alternator and I will
show you how simple this really is.
Take a look at the Delco 10Si and 12 Si
diagram this shows a 3 wire connection with
a charge light. If you don’t have this light the
circuit is the same just eliminate the light.
Note light is wired in series with the ignition
You will see there is 12 volts going directly into
the regulator via pin #2 and 12 volts into pin #1 via the ignition switch and the output is
wired directly to the positive side of the battery.
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If this was a 1 wire alternator no regulator pins 1 & 2 would exist there would be just “1
wire” from the output of the alternator to the battery.
The 3 wire alternator regulator is accessed via 2 pins that sometimes is located under a
dust cover. Remove this dust cover and insert a plug know as “DA plug” this plug is
designed to snap into the alternator regulator and comes with a long wire pin #1 that
goes to the ignition switch or (+ side of coil) same electrical connection and there is
another shorter wire that connects pin #2 to the output side of the alternator.
Special note: you want to make sure that the wire from pin #1 going to the ignition
switch has a diode (one way electrical check valve) to allow current to flow only from the
switch to the alternator, if not, there is a good chance with some older ignition switches
you will not be able to turn off your engine and your battery will be dead in the morning.
Take a closer look at DA plug here
Shows 3 wire alternator connection,
the white wire is the one with the
diode and connects to switched 12
volts. Red wire connects directly to
the battery positive side.
10 Si alternator:
CS130 alternator:
Early engines came with different width generator V belts
depending on make model and year, these pulleys range from
3/8” 1/2” 5/8” 3/4”, to select the correct pulley for your alternator
measure the top width of the belt. All these size pulleys are
available for alternators.
Take closer look at pulleys
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Learn how to convert your vehicle from 6 volts to 12 volts
If you want to keep your
vehicle 6 volts (positive or
negative) ground you can
install an alternator, both are
Take closer look at 6 volt
alternators here:
This diagram that will help you
connect your alternator to your
battery via ammeter. Make
sure you connect your
alternator to battery with
correct size wire.
Take closer look at connection wire here
Note: about keeping your original ammeter in place, there is no need to put a
reducer on ammeters as they read current flow and not voltage. If you have a volt
meter rather than ammeter you may need to add a resistor or recommend adding
an aftermarket ammeter.
Note: here is simple way of testing an alternator after install, with the engine
running take a pocket knife or screw
driver and touch the back of the alternator external bearing
surface. if the alternator is working you will
feel magnetic pull, if not then your alternator is not producing
current make sure your battery is fully charged.
Next you will need to choose an alternator bracket to attach your alternator to your
engine. There are several types of brackets to chose from:
Ford Flathead V8’s use a slingshot style bracket that mounts the alternator in the same
place as the original generator and there are different Flathead V8 brackets to fit
different year engines. You can see some by clicking this link
Chevrolet 1937-1955 1st series straight six 216,235,261 cu inch engines there is a
bracket that fits in the same place as the original generator bracket that lines up the
pulleys perfectly. Take a look here
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Chevrolet 1955 2nd series-1962 straight six 235,261 cu inch engines there is a bracket
that fits in the same place as the original generator bracket that lines up the pulleys
perfectly. Take a look here
For GM Delco made generators found on many makes and model engines these
brackets also mount the alternator in the same place as the generator. You will need to
know if your generator is a long or short case. Long case generators are most
commonly found on latter model engines. To
determine if you have long or short case measure the distance between the generator
mounting ears.
Click this link Short case GM 6.04”
Click this link Long case GM 7.13”
Dodge Plymouth Chrysler typically use autolite generators, there is a bracket that
mounts the alternator in the same location as the generator.
See this bracket here
Ford 1954-64 Y block 292 engines use different types of alternator brackets depending
on what vehicle they are installed in. Ford, Mercury cars and trucks use one type, while
Lincoln use yet another and 1955-1956 T-Bird use another configuration depending on
the alternator selected. Here are some links to see the different brackets.
Ford, Mercury Y block bracket
Lincoln Y block bracket
T-Bird Y block bracket with Ford alternator
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Learn how to convert your vehicle from 6 volts to 12 volts
If none of these brackets work for your application there is a universal bracket that you
construct like an erector set, these are great if you are not certain what generator you
have and will fit just about any generator to alternator configuration.
Take a look here
If you prefer to use your original generator here are some tips how to convert to
12 volts.
You will need to change the field coils to 12 volts and change the voltage regulator.
Start by disassembling the generator which is straight forward. The most difficult area is
the removal of the square headed screws (2 of them) that hold the field
coils. You will need a special wrench to remove these, if hard to
remove carefully heat the area around the screws; this will loosen
the years of dirt and varnish that has built up. After you get
the coils out you can clean and paint the housing. Now install the
new 12 volt field coils and brushes and bushing is needed.
Next use 400-500m grit zinc oxide paper to clean the commentator
segments on the armature.
These are the copper segments that the brushes ride on. Also clean
between the segments, us a small square file or a small blade to
clean in between the segments. To check that your generator
armature is not shorted, use an ohm meter to check from the
commentator to the armature, touch the copper segments to the end
of the bearing shaft, you should not get a reading. If you do,
there may be a short in the armature and you will need to replace
it. If your generator worked when removed, then it should work
after you convert the field coils.
The next tricky area is replacing the bushing on the back of the
generator housing. This is the bushing that the armature shaft bearing rides
in. If it looks good go ahead and reuse. If worn you will need to press in new bearings.
Same with the front housing bearings. If the armature was not dragging on the
field coil segments then chances are the bearing are still good.
Clean them and when assembling use as small amount of white
grease on the rear bearing. Replace the graphite brushes and
reassemble the generator rear housing.
You will need to hold the brushes back carefully while installing
the rear housing, be careful not to get any grease or oil in the
area where the brushes ride on the armature. Your generator is now
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ready to go.
If you don’t want to tackle this, you can send your generator to a shop to make the
conversion and overhaul your generator. We have a good shop that will do this work for
your. contact us for quote. Click here
Here is a link to see generator and regulator conversion kit: Click here
You will need to POLARIZE your generator after conversion. (No need if
installing an alternator). (most fords use a B
circuit) and (most GM cars use an A circuit). This is for an B
circuit. Disconnect the field wire from the regulator and strike it
to the battery terminal of the regulator until you see a spark. Do
not try to use a jumper wire for this, you need to actually remove
the wire to do this correctly. Once you see a spark, reconnect the
field wire to the regulator and you have completed this step.
Now check the voltage coming from your generator by connecting a volt
meter to the regulator battery connection and ground. Low RPM will read around 12
volts which is the battery voltage at higher engine speeds when the cut off switch kicks
in your should read in the area of 14.5 volts.
You are done here and can reinstall the generator and other conversion parts to
complete your project.
There is another alternator option for those that want to keep the original look under the
hood yet have all the advantages of an alternator. These alternators are made by Power
Master and fit perfectly into your specific engine application, there are too many of these
alternators to list here. Here are a few examples of these 90 amp alternators.
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Learn how to convert your vehicle from 6 volts to 12 volts
The ignition coil will need to be replace when converting to 12 volts.
There are 2 types of ignition coils, one with internal ballast resistors and one with
external resistor. Chances are you have a coil now with external ballast resistor and can
change to internal resistance coil just by removing the old ballast resistor. Keep in mind
if your are changing to negative grounded system the negative side of coil goes to the
distributor and positive to the key switch which is opposite on a positive ground
electrical system.
To make your conversion simple we recommend using an internally resistance coil.
Click here
Special note: points and condensers will work fine on 6 or 12 volts, no need
to change provided they are good. Note: a shorted condenser will keep your
engine from starting or will shut it down if it goes bad. Always keep a spare condenser
in the glove box in case you get stuck somewhere with this problem.
If you want to eliminate the points and condenser and keep the original look of your
distributor you can install Electronic Ignition System these are available for most make
and model distributors and will make a difference in engine performance.
For the early Ford Flathead V8 guys with the distributor and coil
mounted on top of distributor you will need to convert and
and mount an external coil.
Ford flathead years 1933-1936
Ford flathead years 1937-1941
You are now ready to tackle the conversion of your Oil, Gas and Temp
gauges. Remember the original gauges were meant to work on 6 volts. If you
apply 12 volts to any 6 volt gauge they will burn up! I recommend the use of a
solid state voltage regulator versus any type of resistor as these work the best and
protect your gauges. The problem with resistors as they heat up the values change and
the gauge will not read correctly. We recommend the VREG
When installing the correct type of 12 to 6 volt gauge regulator you do not need to
change the oil, gas, temp sending units as the gauge and sending units will continue to
operate on 6 volts, this will save you time and expense by keeping your original sending
units and gauges. See gauge regulator here
If you are changing the polarity of your electrical system you will need to switch the
wires on the back of the gauge, if you don’t the gauge will try and read
backwards,nothing bad will happen, just reverse the polarity on the back of the gauge.
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Learn how to convert your vehicle from 6 volts to 12 volts
Special note, you don’t need to put any reducer on the ammeter as stated earlier the
ammeter reads current flow and not voltage sensitive.
If your vehicle has a start solenoid mounted to either the fire wall or starter itself we
highly recommend you replace with a 12 volt solenoid. Your 6 volt solenoid might work
ok on 12 volts for awhile but, you don’t want to get stuck somewhere with a failed
solenoid and can’t find one at the local parts store.
There are several types of solenoids, on the early and even latter model Fords the
solenoid is located on the firewall and is activated via a ground circuit from the start
button, while others require 12 volts to activate, you will need to make sure you select
the correct solenoid for your application.
GM and Chrysler and some others use a solenoid mounted to the starter these are
large cylinders with a plunger that activates the starter gear.
You may have a mechanical foot type starter that are found in early Chevy and Dodge
cars and trucks. There is no need to make any changes to this mechanical system, will
work fine on 12 volts.
If you have a heater with a 6 volt blower motor there is an simple way to keep your
existing heater by installing a reducer for the motor. This link to see will show you what
these look like.
Click this link to learn more
If you have of post war era 6 volt tube radio that you want to use, there is a 12 volt to 6
volt reducer that you can use. More info on radio reducer here
These reducers work well provided your radio works already on 6 volts.
6 volt horns will work on 12 volts because the winding in these old horns are heavy
gage wire and seem to hold up with the short duty cycle horns are used.
You will need to change the horn relay with a 12 volt relay. Check out horn relay here
Next replace all the light bulbs, many of these can be found at the local auto parts store
or there are light bulb kits that will have all the bulbs for your make model vehicle.
Recommend you install a headlight relay to remove the current from the dash light
switch, as these old light switches can cause dim headlights as the contacts become
dirty. The relay works like your modern vehicle electrical system and simple to install.
Here is example of headlight relay.
You will need to find a suitable 12 volt battery that will fit your battery tray, we
recommend a high cracking amp battery that can be found at any local parts store.
Check your battery cable to make sure they are in good condition, you may need to
replace with longer cable when changing from positive to negative ground systems.
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Learn how to convert your vehicle from 6 volts to 12 volts
If you have a Borg Warner Overdrive installed in your vehicle there is no way you can
put any type of reducer on the solenoid or relay to make these work on 12 volts. These
items need to be replaced with 12 volt units.
Here is link to more information on BW OD solenoids and relays and a great book.
Link to OD parts
If your vehicle has an electric clock, you will need to have converted to 12 volts, there a
no 12 to 6 volt reducers for electric clocks. We like the folks at The Clock Works to
rebuild and convert clocks. Link to their site. The Clock Works
Special General Note: Older vehicles use the chassis as a means to ground and
complete the electrical circuit. Make sure all your grounds are tight and have a good
ground between the engine and the chassis. This by fare is is the most
common electrical problem found in all older vehicles.
Enjoy your newly converted vehicle, have fun and be safe!
If you would like to a custom list of conversion parts for your project, you can
sent request via this link. Please include the make and model vehicle and engine
type and year. Please allow a few days for reply.
Jay Johnson
Vintage Auto Garage.
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