possible causes associated with each air-conditioning component. This is by no means a complete list, so you should have the manufacturer's vehicle repair manual handy.

COMPRESSOR

A thumping noise in the compressor or a cool and sweating compressor suction line accompanied by no cooling is usually caused by too much refrigerant in the system. If there is no moisture in the system, the excess refrigerant should be removed and stored for proper disposal. If moisture is present, you must discharge, evacuate, and recharge the system.

CONDENSER

The condenser unit could have clogged fins that limit the cooling ability of the unit. This could be caused by bugs, leaves, or other debris caught in the tins. This can be corrected by using air pressure to blow out the coils, Check for any icy or frosty spots on the condenser. An abnormally cold spot usually indicates partial restriction inside the condenser coils at that point. Restrictions are normally caused by foreign matter. Correct this condition by discharging and purging the system.

EVAPORATOR

The evapator is normally maintenance free for the life of a vehicle. If the evaporator does develop a leak, it will be necessary to remove the assembly for repair. An evaporator is repaired in the same manner as a radiator. If the evaporator does not get the right amount of refrigerant, the expansion valve is most likely at fault.

EXPANSION VALVE

The most common malfunction in the expansion valve is icing caused by moisture in the air-conditioning system. The system must be discharged and evacuated to remove all moisture. On occasion, the expansion valve may stick open or closed; in this case, you must replace the valve.

RECEIVER/DRIER

The receiver/drier may become saturated with moisture or the filter may become restricted. If the receiver/drier is saturated or restricted, replace it. For any of these repairs, comply with the appropriate maintenance manual.

INSPECTING THE AIR-CONDITIONING SYSTEM FOR LEAKS

Approximately 80 percent of all air-conditioning service work consists of your inspecting for and repairing leaks. Many leaks will be located at points of connection and are caused by vehicle vibration. They may only require the retightening of a flare connection or a clamp. Occasionally, a hose will rub on a structural part to create a leak, or a hose may deteriorate and require replacement. The compressor shaft seal may also require. occasional replacement. Anytime the system requires more than one-half pound of refrigerant after operating during one season, a serious leak is indicated that you must locate and repair. The following information covers a few of the various means of detecting leaks.

CAUTION

When any tests or repairs are being made on a charged air-conditioning system, always wear adequate eye protection.

INTERNALLY CHARGED DETECTOR

This detector is a specially colored leak detector available in a pressurized can and mixed with R-12. It can be introduced into the air-conditioning system with regular charging equipment. When a leak occurs in the system, a bright red-orange spot appears at the point of leakage and remains until it is wiped off. The internal leak detector remains in the system and will spot future leaks in the same manner. A sticker is usually placed under the vehicle hood to indicate that the system is charged with a leak detector.

BUBBLE DETECTOR

The bubble detector is a solution applied externally at suspected leak points. Leaking refrigerant will cause the detector to form bubbles and foam.

ELECTRONIC DETECTOR

This instrument indicates leaks electronically by flashing a light or sounding an alarm. There are several different types of electronic detectors. Directions for using the instruments are furnished by the manufacturer.