AIR CONDITIONING SYSTEM TROUBLESHOOTING AND TESTING

TM 9-2320-303-24-2

AIR CONDITIONING SYSTEM TROUBLESHOOTING AND TESTING

THIS WORK PACKAGE COVERS

Preliminary Checks, Performance Tests, Safety Precautions, Air Conditioning System Components, Air Conditioning

Troubleshooting

INITIAL SETUP

Tools and Special Tools

Tool kit, general mechanic's (Item 102, WP 0313 00)

PRELIMINARY CHECKS

Before testing the operation of the air conditioning system, make the following checks:

Ensure the refrigerant compressor's drive belt is not damaged and is correctly tensioned. Also check the compressor

mountings for tightness.

Check for broken, burst or cut hoses; also check for loose fittings on all parts.

Check for road debris buildup on the condenser coil fins. Using air pressure and a whiskbroom or a soapy spray of

water, carefully clean off the condenser; be careful not to bend the fins.

Check the color of the moisture indicator sight glass. If the color is a deep cobalt blue, the refrigerant charge is dry. If the

indicator is not blue, the system is contaminated with moisture. Recover the refrigerant, evacuate the system, replace the

receiver-dryer, and add a full refrigerant charge (WP 0297 00).

If there is not enough airflow, ensure leaves or other debris have not entered the fresh air ports under the windshield. If

debris has entered, it could clog the fins of the evaporator core, and block airflow. Also, be sure that all ducts are con-

nected to the dash louvers and that the air-control flaps in the heater housing are moving properly (this requires removal

of the right and center dash panel).

PERFORMANCE TESTS

Following is a brief description of symptoms or conditions that could exist if something goes wrong with a refrigerant

part.

Receiver-Dryer.

The receiver-dryer is normally at outside temperature. To the touch, the entire length of the unit should be the same

temperature. If noticeable cool spots exist, replace receiver-dryer (WP 0303 00).

A blockage at the inlet of the unit will cause high head pressures; outlet blockages will cause low head pressures

and little or no cooling.

If the moisture indicator is pink or white (showing that the system is wet), the receiver-dryer is saturated with

moisture and must be replaced (WP 0303 00).

Cooling System.

Although they are not physically connected, there is a close tie between vehicle's air conditioner and cooling sys-

tem. Poor air conditioner cooling can be the result of a problem in the cooling system.

If the cooling system does not work correctly, the heat of the engine will rise to abnormal levels. The added heat

will transfer to the air conditioner, other underhood parts, and may make its way into the cab. The added heat

makes it necessary for the air conditioner to work harder and, at the same time, it reduces the air conditioner's abil-

ity to cool down the air in the cab. Also, if the water regulating valve isn't closing all the way, heat will enter the

cab, giving the impression that the air conditioning system is not working.