A/C The Basics
an ISO 9001: 2008 Registered Company
18865 Goll St San Antonio, TX 78266 PH 210.654.7171 FAX 210.654.3113
1.800.TO.COOL.U (862-6658) www.vintageair.com
The Basics of Performance Air Conditioning
The primary purpose of air conditioning is to remove heat and humidity from inside the vehicle.
How the system works:
Refrigerant absorbs heat as it changes states from a liquid to a gas in the evaporator, and then dissipates heat as it changes from a gas to a liquid in the condenser.
Heat is absorbed through evaporation, and dissipated through condensation (Change of states).
Refrigerant is a high-pressure liquid (high side), and a low-pressure gas (low or suction side).
List of basic air conditioning components, and their purpose:
Evaporator with expansion valve: Evaporator absorbs heat/humidity; valve regulates the flow of refrigerant.
Compressor: Pumps refrigerant through system.
Condenser: Cools refrigerant to induce change from gas to liquid.
Receiver/Drier: Filters refrigerant, separates vapor from liquid refrigerant, and removes moisture.
Safety Switches (Two Types: Binary and Trinary):
Binary: High (406 PSI) and Low (30 PSI) pressure protection.
Trinary: High (406 PSI) and Low (30 PSI) pressure protection, plus an electric fan engagement signal at 254 PSI (on high pressure side).
Thermostat: Adjusts compressor cycle time (indirect temperature control).
NOTE: Explain evaporator freeze up (internal & external).
R-134a is a more efficient absorber and carrier of heat than CFC-12, hence the need for a larger or more-efficient condenser with R-134a refrigerant to keep high side pressures within an acceptable range.
R-134a molecules are smaller and, as such, require O-ring fittings and crimped barrier hose connections (beadlock recommended, no clamps).
Crimps: R-134a standard is beadlock. Always recommended!
Always fill by volume 1.8 lbs using a good scale (Standard Vintage Air System).
NOTE: 1.8 lbs = 28.8 oz. Extremely long liquid line or suburban size condenser would require additional charge.
Blends/Replacements: Vintage Air does not recommend blends.
When to consider air conditioning for your project:
Very early in the planning/building phase.
Mount engine far enough back to allow for condenser, fan, shroud and radiator.
Use largest evaporator possible.
Install evaporator in dash/cowl area first, and position other components around it.
Do not distort compressor body when mounting (May cause oil leak).
Use minimum “Grade 5” bolts & sturdy, supportive bracket.
Align pulleys well!
At least 1/3” belt wrap (Belt should contact/drive sides of pulley, and should not bottom out in groove).
R134a oil: Pag 016. Sanden recommends SP-20 oil.
90° maximum "clocking" to retain oil on Sanden SD508 compressor.
Clutch air gap: .016 - .031.
Mount upright in air flow or cool area (May be mounted inside vehicle).
Drier/safety switch combination is a convenient way to package safety switch.
In front of radiator, up to 3/16” gap. Do not place against radiator.
1 ¼ volume of evaporator coil (in³).
Parallel-flow condenser has 25% more capacity than same size tube & fin.
Under-car condenser not recommended for 134a (As primary condenser).
Remember: Temperature differential induces heat transfer. Air under the car is much warmer and more stagnant than clean air coming at the front of the car.
Size evaporator to car (Always try to package the largest evaporator possible).
Mount solid and level. Pay attention to the drain hole and tube!
Seal and insulate car!
Stretch duct hose to eliminate “ribbing” and reduce turbulence. Route duct hose with smooth, gentle bends. Try not to kink or crush.
Never cap unused evaporator outlets! This creates cavitation and “cold spots” in the coil, which may lead to evaporator freeze up.
Do not completely seal off under dash (air can not recirculate to blower).
Cool air drops, so locate vents high enough to blow air on/past people.
Seal and insulate the cabin area (including cowl and above evaporator).
Make sure your cooling system and radiator are sufficient.
Remember: Without adequate airflow, a radiator is just a reservoir for hot water. In general, coolant transfers heat to radiator tubes, tubes transfer heat to fins, and movement of air through the fins removes heat from the radiator. You must allow air to pass efficiently through the radiator and out!
Allow for air to escape from under hood.
Ensure radiator cap has the proper pressure rating:
With Walker Radiator or aftermarket: 15-18 lb. cap (Each 1 lb of increased pressure raises the boiling point 3° F).
On original recore radiator: 4-7 lb. cap (Tanks are not designed to hold pressure).
Remember: Antifreeze (now called antifreeze/coolant) increases the boiling point of water.
Corrosion inhibitors protect against scaling and mineral build-up that can reduce heat transfer.
Proper mix is 50% coolant to 50% water. Use distilled water or pre-mix antifreeze.
Proper maintenance (flushing & changing coolant) will extend the life of the system.
Always use a shroud with an engine-driven fan, as it will dramatically improve the efficiency of the fan. An unshrouded fan moves about 50% of the air volume of a shrouded fan, because it only moves air through the portion of the radiator equal to the surface of the fan, and does not benefit from the housing effect that the shroud provides.
NOTE: For best performance, when installing a fan shroud, locate the fan 1/2 to 2/3 inside the shroud.
Water pumps should be overdriven 30 to 35% (Pulley ratio: Crankshaft pulley should be 30% larger than water pump pulley).
Always use a thermostat to control engine temperature.
Basic Air Conditioning
#6 Liquid Line
# 10 Suction Hose
Low-Side Charge Port
High-Side Charge Port
# 8 Discharge
#6 Liquid A/C Hose
(Condenser to Evaporator)
#8 Liquid A/C Hose
(Compressor to Condenser)
#10 Suction A/C Hose
(Evaporator to Compressor)
Direction of Refrigerant Flow
Indicated By Arrows
The Evaporator absorbs heat from interior air as liquid spray droplets change to gas vapor.
Functions of the A/C
The Expansion Valve regulates refrigerant flow and drops the liquid pressure. This pressure split changes the refrigerant to a very cold vaporizing liquid spray.
The Compressor is a refrigerant gas circulating pump which draws low pressure, medium temperature vapor from the evaporator, and raises the pressure and temperature.
- A Binary Switch
compressor clutch with
pressure or low threshold
pressure (loss of refrigerant).
- A Trinary Switch combines
Binary functions with a fan
The Condenser dissipates heat to ambient air, and changes refrigerant to a high pressure liquid.
High Pressure Refrigerant
Low Pressure Refrigerant
The Receiver/Drier separates liquid from vapor. The Receiver/Drier contains desiccant and filters to remove moisture, acid and contamination.
Capillary Tube Insertion
Typical Electric Fan Relay Wiring With Trinary Switch
Note: Trinary Switch Connection for Part Number 11076-VUS Shown
Trinary Switch Part # 11076-VUS
High Pressure Cutoff - 406 psi
Low Pressure Cutoff - 30 psi
Electric Fan Engagement - 254 psi
Preset Pressure For Fan Relay Ground
Optional Fan Temp Switch In Engine
Self Grounding or Separate Ground
Terminal Type (190° Part # 11190-VUS)
Fan In Radiator
(Part # 24675-VUT)
Tube & Fin
Mechanically assembled core with brazed return bends on one end.
Extruded core with radiused return bends on one end and brazed fins.
Molecule CH FCF
Extruded straight tubes with brazed fins between tubes and brazed tanks.
THIS STICKER LOCATED
ON TOP SIDE OF
SLIDE TYPE THERMOSTAT
THRU THIS HOLE.
ENTIRE THICKNESS OF
AIR CONDITIONING ADJUSTMENTS:
YOUR SYSTEM MAY HAVE A ROTARY OR SLIDE TYPE
THERMOSTAT. IF YOU ARE UPGRADING TO A NEW
CONTROL PANEL, USE THE THERMOSTAT INCLUDED
WITH THE NEW PANEL. REMOVE YOUR ORIGINAL
THERMOSTAT AND DISCARD.
• THE AIR CONDITIONER THERMOSTAT CONTROLS COIL TEMPERATURE. ROTARY TYPE THERMOSTATS ARE
SHIPPED ADJUSTED FULLY COLD (CLOCKWISE). IN THE MAJORITY OF CASES, THE A/C WILL OPERATE
CORRECTLY AS SHIPPED.
• TURNING THE KNOB ON THE ROTARY TYPE THERMOSTAT TO THE RIGHT (CLOCKWISE) MAKES THE SYSTEM
OPERATE COLDER. MOVING THE LEVER TOWARD COLDER ON THE SLIDE TYPE THERMOSTAT MAKES THE
SYSTEM OPERATE COLDER. IF THE THERMOSTAT IS SET TOO COLD, THE EVAPORATOR COIL WILL
"ICE UP," M EANING, THE EVAPORATOR COIL IS RESTRICTED WITH ICE AND COLD AIR FLOW WILL BE REDUCED.
• TURNING THE KNOB TO THE LEFT (COUNTERCLOCKWISE) ON A ROTARY TYPE THERMOSTAT MAKES THE
SYSTEM OPERATE WARMER. MOVING THE LEVER TOWARD THE RED LINES ON A SLIDE TYPE THERMOSTAT
ADJUSTING A/C THERMOSTAT
1.) SYMPTOM: THE A/C WORKS WELL AT FIRST THEN QUITS COOLING. THE AIR FLOW FROM THE
VENTS IS LOW, AND THE COMPRESSOR CLUTCH CYCLES INFREQUENTLY.
SOLUTION: THE THERMOSTAT IS SET TOO COLD AND THE EVAPORATOR IS "ICING UP" AND RESTRICTING
AIR FLOW. ALLOW THE ICE TO MELT AND SET THE ROTARY TYPE THERMOSTAT WARMER (COUNTERCLOCK-
WISE) 1/8 OF A TURN EACH ADJUSTMENT UNTIL THE SYMPTOMS DIMINISH.
ADJUST THE SLIDE TYPE THERMOSTAT IN 1/8" INCREMENTS TOWARD THE SMALLER BLUE GRADIENTS, UNTIL
THE SYMPTOMS DIMINISH.
2.) SYMPTOM: A/C NEVER GETS COLD AND THE COMPRESSOR CLUTCH CYCLES FREQUENTLY.
SOLUTION: THE THERMOSTAT IS SET TOO WARM. SET THE ROTARY TYPE THERMOSTAT COLDER (CLOCKWISE)
1/8 OF A TURN EACH ADJUSTMENT, UNTIL THE DESIRED AIR TEMPERATURE IS REACHED. ADJUST SLIDE TYPE
THERMOSTAT IN 1/8" INCREMENTS TOWARDS COLDER UNTIL THE DESIRED AIR TEMP IS REACHED.
AVOID SETTING THE THERMOSTAT TOO COLD.
3.) SYMPTOM: THE A/C NEVER GETS COLD, SOMETIMES EVEN BLOWS HOT, AND THE A/C COMPRESSOR
CLUTCH INFREQUENTLY CYCLES OFF.
SOLUTION: THE HEATER MAY BE ON AT ALL TIMES. CAREFULLY FEEL THE HEATER HOSE BETWEEN THE
EVAPORATOR AND THE HEATER CONTROL VALVE. THIS HOSE SHOULD NOT BE HOT IN THE A/C MODE.
IF THE HOSES ARE HOT:
A)- THE HEATER CONTROL VALVE MAY BE INSTALLED BACKWARDS. CHECK THE FLOW DIRECTION
ARROW ON THE VALVE AGAINST THE ILLUSTRATION IN YOUR INSTALLATION INSTRUCTIONS.
B)- IF CABLE OPERATED: THE VALVE MAY BE MISADJUSTED.
C)- IF VACUUM OPERATED: IT MAY BE GETTING VACUUM AT ALL TIMES (CHECK ELECTRIC SOLENOID).
D)- THE HEATER CONTROL VALVE MAY BE INSTALLED IN THE WRONG HOSE. IT MUST BE INSTALLED
IN THE HOSE COMING FROM THE INTAKE MANIFOLD ENGINE COOLANT PRESSURE PORT.
The following guide will help the installer determine if a problem that would cause a malfunction exists in the system.
If you are experiencing problems in the physical operation of the unit (blower speeds, door operation, etc.), we encourage you to
refer to the wiring diagram located in the instruction manual. Using a continuity or light tester, you can solve many of the simple problems by tracing all connections and testing them individually. However, if the unit is functioning correctly, but it is not cooling, you can refer to the following guide that will outline the most common problems encountered by installers.
Test conditions used to determine system operation:
Place temperature probe (thermometer) into center outlet.
Connect gauges or service equipment to the high/low charging ports.
Place blower fan switch on medium.
Close all doors and windows on vehicle.
Place shop fan or heavy duty squirrel-cage blower directly in front of the condenser.
Run engine idle up to 1,500 RPM.
(These test conditions will simulate the effect of driving the vehicle, and will give the technician the three critical readings needed to diagnose any potential problems.)
Acceptable operating pressure ranges for Vintage Air systems:
High-side pressure: 160 to 250 PSI. NOTE: A general rule of thumb is two
times the ambient (daytime) temperature, plus 15 to 20%.
Low-side pressure: 6 to 18 PSI in a steady state.
Center duct temperature: 36 to 46° F.
High-side pressure: 140 to 230 PSI. NOTE: A general rule of thumb is two
times the ambient (daytime) temperature, plus 15%.
Low-side pressure: 12 to 15 PSI in a steady state.
Center duct temperature: 36 to 46° F.
Charge as follows: R134a = 1.8 lbs. R-12 = 2.0 lbs.
No additional oil is necessary in new compressors
Typical problems encountered when charging a system:
A noisy compressor is generally caused by overcharging the system or introducing outside air into the system.
If a system is overcharged, both gauges will register abnormally high readings. Overcharging causes a feedback pressure on the compressor, which results in the compressor rattling or shaking from the increased cylinder head pressures. To correct, the system must be evacuated and recharged to exact weight specifications.
If air is introduced into the system during charging, it will introduce moisture that will cause ice to form in the refrigerant flow, and will cause the compressor to rattle or growl under acceleration. To correct, the system must be evacuated and recharged to exact weight specifications, making sure to bleed any air from the lines when introducing the refrigerant.
System not cooling:
There are a number of factors that can cause the cooling to be less than optimal.
Improper charge in system: Improper charging is the number one cause of system failure. Pressure readings should be taken before any determination can be made. High or low readings in direct proportion to the normal pressures (See Section II) will tell you if the charge is too high or too low. Excessive system pressure can also cause vibrations and whistling noises from the expansion valve and refrigerant lines.
Heater control valve installation: Failing to install the heater control valve in the correct hose will allow water to collect in the unit.
NOTE: The heater control valve is a directional valve. Make sure the water flow
follows the direction of the arrow. As the engine heats up, the water transfers heat to the coil, thus overpowering the A/C coil. A leaking or faulty valve will have a more pronounced effect on the unit’s cooling ability.
Installing the valve improperly (such as having the flow reversed) will allow water to flow through, thus inhibiting cooling. Check for heat transfer by disconnecting the hoses from the system completely. By running down the road with the hoses looped back through the motor, you eliminate the possibility of heat transfer to the unit. Move or replace the valve if necessary.
Evaporator freezing: Freezing can occur both externally and internally on an evaporator core.
External freeze up occurs when the coil cannot effectively displace the condensation on the outside of the fins, and the water forms ice (the evaporator core resembles a block of solid ice). It restricts the flow of air that can pass through it, which gives the illusion of the A/C not functioning. The common cause of external freezing is the setting of the thermostat and the presence of high humidity in the passenger compartment. All door and window seals should be checked in the event of constant freeze up. A thermostat is provided with all units to control the cycling of the compressor. The gas-filled probe will often come coiled up and must be installed into the coil through the access hole located in the top of each unit.
NOTE: The rotary-type thermostat should be set all the way clockwise and turned back counterclockwise an eighth of a turn. The lever-type thermostat should be backed away from the cold position slightly.
Internal freeze up occurs when there is too much moisture inside the system. The symptoms of internal freeze up often surface after extended highway driving. The volume of air stays constant, but the temperature of the air gradually rises. When this freezing occurs, the low side pressure will drop, eventually going into a vacuum. At this point, the system should be checked by a professional who will evacuate the system and change the drier.
Inadequate airflow to condenser: The condenser works best in front of the radiator with a large supply of fresh air. Abnormally high pressure will result from improper airflow. Check the airflow requirements by placing a large-capacity fan in front of the condenser and running cool water over the surface. If the pressure drops significantly, this indicates the need for better airflow.
Incorrect or inadequate condenser capacity: Incorrect condenser capacity will cause abnormally high head pressure. Vintage Air recommends at least 300 cubic inches of fin area on a double-pass (two rows of tubes) condenser. This can be measured by multiplying (Height x
Width x Thickness). This rule applies only to tube-and-fin style condensers.
The efficiency of the SuperFlow™ design allows the use of a smaller area.
A quick test that can be performed is to run cool water over the condenser while the system is operating. If the pressure decreases significantly, it is likely an airflow or capacity problem.
Expansion valve failure: An expansion valve failure is generally caused by dirt or debris entering the system during assembly. If an expansion valve fails, it will be indicated by abnormal gauge readings.
A valve that is blocked will be indicated by the high side being unusually high, while the low side is unusually low, with the low side even going into a vacuum in some cases.
A valve that is stuck open by both the high- and low-side pressures rising to unusually high readings, seeming to move toward equal readings on the gauges.
Restrictions in the system: A restriction in the cooling system will cause abnormal readings on the gauges. A high-side restriction (between the compressor and the drier inlet) will be indicated by the discharge gauges reading excessively high.
These simple tests can be performed by a local shop, and can help determine the extent of the systems problem.
If further assistance is needed, our tech line can be reached at
(210) 654-7171. If you have performed the initial tests, please document the results and readings before calling our technical line, as it will help us solve the problem more quickly.
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