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 1
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 (either from the motion of the car or the action of the fans), heat is removed from the gas. Now cooled, the gas condenses into a liquid and flows into the receiver/dryer. The receiver/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.
Once in the evaporator, (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.
A lot of A/C problems can be avoided by running the air conditioner at least once a week, regardless of the season. Simply let the system run for at least 5 minutes a week (even in the winter), and you'll keep the internal parts lubricated as well as preventing the hoses from hardening.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.Check the A/C Compressor Belt
The compressor drive belt should be checked frequently for tension and condition. Refer to the information in this section on "Belts".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.Additional Preventive Maintenance Checks
In order to prevent heater core freeze-up during A/C operation, it is necessary to maintain permanent type antifreeze protection of +15°F, or lower. A reading of -15°F is ideal since this protection also supplies sufficient corrosion inhibitors for the protection of the engine cooling system.
The same antifreeze should not be used longer than the manufacturer specifies.RADIATOR CAP
For efficient operation of an air conditioned car's cooling system, the radiator cap should have a holding pressure which meets manufacturer's specifications. A cap which fails to hold these pressures should be replaced.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.
REFRIGERANT LEVEL CHECKS
See Figure 2
If your car is equipped with an aftermarket air conditioner, the following system check may not apply. Contact the manufacturer of the unit for instructions on system checks.
The easiest way to check the air conditioning is to turn it on; if cold air is supplied, the system is probably in good order. A properly charged system which is used frequently is not likely to need maintenance. It is not uncommon to find cars several years old running on the original charge in the system. If working properly, the system does not require periodic recharging.
If a problem is suspected, the first order of business when checking the refrigerant is to find the sight glass. It is usually located in the head of the receiver/drier at the left front corner of the engine compartment. Due to the recessed locations of some receive/driers, the glass may be located in its own block, anywhere in the liquid line running to the evaporator. It should be visible by looking at the air conditioning lines running across the engine compartment near the radiator.
Once you've found it, wipe off the small glass window and proceed as follows:
- With the engine running and the air conditioner switched on inside the vehicle, look for the flow of refrigerant through the sight glass. If the system is working properly, you'll see a continuous flow of clear refrigerant in the sight glass, with perhaps an occasional bubble if the system is operating at high temperatures.
- Cycle the air conditioner on and off to make sure what you are seeing is refrigerant. Since the fluid 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 see no bubbles when the system is running and cold air is flowing from the air vents inside, the system is OK.
The air conditioning system may turn itself off automatically to prevent the evaporator from freezing. If this happens while you're looking at the sight glass, don't mistake it for a failure. Wait a short while and the system will re-engage.
- If you observe bubbles in the sight glass while the system is operating, the system is low on refrigerant. The only reason for this is a leak somewhere; have it checked by a professional. Running the air conditioning with an insufficient charge may damage the compressor.
- Oil streaks in the sight glass are an indication of trouble. Most of the time, oil will appear as a series of streaks although it may also be a solid stream. In either case, it means reduced cooling and possibly compressor replacement.
See Figure 3
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
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.