See Figure 1
R-12 refrigerant is a chlorofluorocarbon which, when released into the atmosphere, contributes to the depletion of the ozone layer. 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. It is also likely that you will not be able to purchase R-12 without proof that you are properly trained and certified to work on A/C systems.
See Figure 2
A lot of A/C problems can be avoided by simply running the air conditioner at least once a week, regardless of the season. Let the system run for at least five minutes a week (even in the winter), and you'll keep the internal parts lubricated and prevent the hoses from hardening.
Refrigerant leaks show up as oily areas on the components because the compressor oil is transported around the entire system with the refrigerant. Look for oily spots on all the hoses and lines, and especially on the hose and tubing connections. If there are oily deposits, the system may have a leak. A small area of oil on the front of the compressor is normal and no cause for alarm.
The compressor drive belt should be checked frequently for proper tension and condition. Refer to the portion of this section on "Belts".
Periodically inspect the front of the condenser for bent fins or foreign material (dirt, bugs, leaves, etc.). If any cooling fins are bent, straighten them carefully with needle nosed pliers. You can remove any debris with a stiff bristle brush or hose.
REFRIGERANT LEVEL CHECK
See Figure 3
The first order of business when checking the refrigerant level is to find the sight glass. It is located in the head of the receiver/drier. Once you've found it, wipe it clean and proceed as follows:
- With the engine and the air conditioning system running, look for the flow of refrigerant in the sight glass. If the air conditioner is working properly, you'll be able to see a continuous flow of clear refrigerant through the sight glass, with perhaps an occasional bubble at very high temperatures.
- Cycle the air conditioner on and off to make sure what you are seeing is clear refrigerant. Since the refrigerant is clear, it is possible to mistake a completely discharged system for one that is fully charged. Turn the system off and watch the sight glass. If there is refrigerant in the system, you'll see bubbles during the off cycle. If you observe no bubbles when the system is running, and the air flowing from the unit in the car is cold, everything is OK.
- If you observe bubbles in the sight glass while the system is operating, the system may be low on refrigerant. It should be noted that some late model cars are equipped with an automatic temperature switch which will turn the system off even though the dash controls are still on. If you are seeing bubbles in the sight glass, open the car doors for a few minutes. The system should switch back on and the bubbles will disappear. The system switching on and off is accompanied by a loud click as the compressor engages and disengages.
- Oil streaks in the sight glass are an indication of trouble. Most of the time, if you see oil in the sight glass, it will appear as a series of streaks, although occasionally it may be a solid stream of oil. In either case, it means that part of the charge has been lost. This is almost always accompanied by a reduction in cold air output within the car.
Once the air conditioning system is fully charged and free of leaks, it is ready to operate on demand. When turned on, the compressor discharges high temperature and high pressure refrigerant. This refrigerant gas contains heat transferred from inside the car plus the heat developed by the compressor on the discharge stroke.
This gaseous refrigerant flows into the condenser. Because of the airflow through the condenser, heat is removed from the gas. Now cooled, the gas condenses into a liquid and flows into the suction accumulator/drier. The suction accumulator/drier stores the liquid refrigerant and filters out small amounts of moisture which may be present.
Flowing from the receiver, the liquid refrigerant passes through an expansion valve which changes it into a low temperature, low pressure mixture of gas and liquid. This cold and foggy refrigerant flows to the evaporator/blower unit.
Once in the evaporator core, (inside the cabin of the vehicle) the refrigerant is exposed to the warmer air being moved by the blower fan. The refrigerant changes to a gas within the evaporator and absorbs heat from the air being circulated by the fan. After being fully vaporized within the evaporator, the heated refrigerant gas is drawn out of the evaporator to the compressor where the cycle continues.
The efficiency of any air conditioning system is controlled not only by the system itself but by outside factors such as air temperature, humidity, forward speed of the car and amount of sunlight entering the car.
CHECKING FOR A/C OIL LEAKS
Refrigerant leaks show up only as oily areas on the various components because the compressor oil is transported around the entire system along with the refrigerant. Look for oily spots on all the hoses and lines (especially on the hose and tube connections). If there are oily deposits, the system may have a leak, and you should have it checked by a qualified mechanic.
CHECKING THE A/C COMPRESSOR BELT
The compressor drive belt should be checked frequently for tension and condition. Refer to the earlier portion of this section regarding belt inspection and adjustment.
KEEP THE A/C CONDENSER CLEAR
The condenser is mounted in front of the radiator (and is often mistaken for the radiator). It serves to remove heat from the air conditioning system and to cool the refrigerant. Proper air flow through the condenser is critical to the operation of the system.
Periodically inspect the front of the condenser for bent fins or foreign material (dirt, bugs, leaves, etc.). If any cooling fins are bent, straighten them carefully with needle nose pliers. You can remove any debris with a stiff bristle brush or hose.
See Figure 4
Generally described, this tool is a set of two gauges, a manifold and three hoses. By connecting the proper hoses to the car's system, the gauges can be used to "see" the air conditioning system at work. Do not use the gauge set as a means for discharging the system.
DISCHARGING, EVACUATING AND CHARGING
If anything indicates a low charge or loss of refrigerant, the system must be discharged (emptied) and refilled to the proper level. It is not acceptable to simply add refrigerant to a partially discharged system.
Discharging, evacuating and charging the air conditioning system must be performed by a properly trained and certified mechanic in a facility equipped with refrigerant recovery/recycling equipment that meets SAE standards for the type of system to be serviced.