The purpose of the air conditioning system is to maintain a comfortable environment inside the passenger compartment by controlling air temperature, circulation, humidity and purifying the air. The air conditioning system is designed to cycle a compressor on and off to maintain the desired cooling within the passenger compartment. Passenger compartment comfort is maintained by the temperature lever located on the control head. The system is also designed to prevent the evaporator from freezing.
When an air conditioning mode is selected, electrical current is sent to the compressor clutch coil. The clutch plate and the hub assembly is then drawn rearward which engages the pulley. The clutch plate and the pulley are then locked together and act as one unit. This in turn drives the compressor shaft which compresses low pressure refrigerant vapor from the evaporator into high pressure. The compressor also circulates refrigerant oil and refrigerant through the air conditioner system. On certain models, the compressor, is equipped with a cut-off solenoid which will shut the compressor off momentarily under certain conditions. These include wide-open throttle and low idle speeds.
R-12 is a chlorofluorocarbon, which when released into the atmosphere, contributes to the depletion of the ozone layer in the upper atmosphere. Ozone filters out harmful radiation from the sun.
Consult the laws in your area before servicing the air conditioning system. In some states it is illegal to perform repairs involving refrigerant unless the work is done by a certified technician.
- Remember to wear safety glasses, especially when working around the air conditioning system.
- Avoid contact with a charged refrigeration system, even when working on another part of the air conditioning system or vehicle. If a heavy tool comes into contact with a section of copper tubing or a heat exchanger, it can easily cause the relatively soft material to rupture.
- When it is necessary to tighten a fitting that contains refrigerant, as when checking that all system couplings are securely tightened, use a wrench on both parts of the fitting involved. This will avoid putting excessive torsional stress on refrigerant tubing. It is advisable to use tube or line wrenches when tightening these flare nut fittings.
- Discharging and charging must be done by a facility that is equipped with a refrigerant recovery system, since refrigerant should not be released into the atmosphere. Do NOT attempt to discharge the system by merely loosening a fitting, or removing the service valve caps and cracking these valves.
- Always have the air conditioning system completely discharged if the vehicle is to be painted and the paint is to be baked on, or before welding anywhere near the refrigerant lines.
System Off Checks
- Check the fins of the condenser for blockage or damage. Carefully remove any debris (bugs, dirt, etc.) from the fins. Be careful not to damage the fins. Any obstruction of or damage to the condenser configuration will restrict the air flow which is essential to its efficient heat transfer operation. It is therefore, a good rule to keep this unit clean and in proper physical shape.
- Check that the drive belt is properly tensioned and is positioned properly in the grooves of the compressor pulley. Adjust the tension of the belt as required.
- Check for kinks in the refrigerant lines or loose electrical wiring.
- Check the antifreeze. In order to prevent heater core freeze-up during air conditioning operation, it is necessary to maintain permanent type antifreeze protection of +15°F (9°C) or lower. A reading of -15°F (-26°C) is ideal since this protection also supplies sufficient corrosion inhibitors for the protection of the engine cooling system.
- Check the radiator cap. For efficient operation of an air conditioned car's cooling system, the radiator cap should have a holding pressure of 14.9 psi. A cap which fails to hold these pressure should be replaced.
- Check the condensation drain tube. This single molded drain tube expels the condensation, which accumulates on the bottom of the evaporator housing, into the engine compartment. If this tube is obstructed, the air conditioning performance can be restricted and condensation buildup can spill over onto the vehicle's floor.
- Start the engine and turn the air conditioning switch to the On position. Have someone cycle the blower switch and make sure the air conditioning unit operates at all positions of the switch.
- Check the operation of the magnetic clutch in warm weather. If the clutch does not engage, check the air conditioning fuse. When the clutch is engaged, the engine idle rpm should increase to 900-1000 rpm. Depress the accelerator pedal. The air conditioning clutch should remain engaged when the engine rpm is raised. Also, check the clutch bearing for noise and grease leakage.
- Lightly touch the compressor lines. The suction line (low pressure) should be cold and the discharge line (high pressure) should be hot.
- Listen for any unusual noises or vibration. Look for loose tubing and hose clamps.
- Check the refrigerant level in the sight glass.
- Check the operation of the condenser fan cooling motor. The fan operates at two speeds depending on the water temperature and the position of the air conditioning switch. The fan must rotate smoothly.
- If you have a leak detector, check all hoses and fittings for leaks.
REFRIGERANT LEVEL CHECKS
You can safely make a few simple checks to determine if your air conditioning system needs service. The tests work best if the temperature is warm, about 70°F (21.1°C).
- Place the automatic transaxle in Park or the manual transaxle in Neutral. Set the parking brake.
- Have a companion run the engine at a fast idle (about 1,500 rpm).
- Set the controls for maximum cold with the blower on High.
- Locate the sight glass on the top of the receiver. The sight glass may be dirty, so wipe it first to ensure a good view.
- If you see foam or bubbles, the system is low and must be charged.
- If there are no bubbles, there is either no refrigerant at all or the system is fully charged. Feel the two hoses going to the belt driven compressor. If they are both at the same temperature, the system is empty and must be recharged.
- If one hose (high pressure) is warm and the other (low pressure) is cold, the system may be all right.
- Have a companion turn the fan control on and off to operate the compressor clutch. Watch the sight glass.
- If bubbles appear when the clutch is disengaged and disappear when it is engaged, the system is properly charged.
- If the refrigerant takes more than 45 seconds to bubble when the clutch is disengaged, the system may be overcharged. This usually causes poor cooling at low speeds.
Some of the service work performed in air conditioning requires the use of a set of two gauges, one for the high (head) pressure side of the system, the other for the low (suction) side. Vacuum and pressure gauges enable you to tell what is happening inside the system and are necessary components for effective troubleshooting and system maintenance.
The low side gauge records both pressure and vacuum. Vacuum readings are calibrated from 0 to 30 inches and the pressure graduations vary according to the type of gauge set that you are using. The high side gauge measures pressure from 0 to at least 60 psi.
Both gauges are threaded into a manifold that contains 2 hand shut-off valves. Proper manipulation of these valves and the use of the attached test hoses allow the user to check the pressures of the system, but discharging and recharging should be performed by a certified facility equipped with refrigerant recovery/recycling equipment that meets sae standards.
The manifold valves are designed so that they have little effect on gauge readings, but serve only to provide for, or cut off, flow of refrigerant through the manifold. During all testing and hook-up operations, the valves are kept in a closed position to avoid disturbing the refrigeration system.
DISCHARGING, EVACUATING AND CHARGING
Discharging, evacuating and charging the air conditioning system should be performed by a certified facility equipped with refrigerant recovery/recycling equipment that meets sae standards.
A visual inspection can reveal signs of a refrigerant leak. Whenever refrigerant escapes, refrigerant oil also escapes, resulting in a yellowish, dirt-attracting accumulation at the leak. This frequently occurs at fittings and on hoses. A minor accumulation at the front compressor seal is normal.
There is a piece of electronic equipment that detects the presence of refrigerant. It makes a beeping sound when the "sniffer" is at the source of a leak.