TM 9-2320-363-34-1TROUBLESHOOTING AND TESTING THE AIRCONDITIONING SYSTEM(All Except M915A2 and M916A1)Preliminarv Checkscool spots exist, replace the receiver-drier.Before testing the operation of the air conditioningsystem, make the following checks:1.2.3.4.5.Make sure the refrigerant compressor’sdrive belt is not damaged and is correctlytensioned. Also check the compressormountings for tightness.Check for broken, burst, or cut hoses; alsocheck for loose fittings on all parts.Check for road debris build-up on thecondenser coil fins. Using air pressure anda whiskbroom or a soapy spray of water,carefully clean off the condenser; be carefulnot to bend the fins.Check the color of the moisture indicatorsight glass. If the color is a deep cobalt blue,the refrigerant charge is dry. If the indicatoris not blue, the system is contaminated withmoisture; recover the refrigerant, evacuatethe system, replace the receiver-drier, andadd a full refrigerant charge.If there is not enough airflow, make sure thatleaves or other debris has not entered thefresh air ports under the windshield. If debrishas entered, it could clog the fins of theevaporator core, and block airflow.Also, be sure that all ducts are connected tothe dash louvers and that the air-controlflaps in the heater housing are movingproperly (this requires removal of the rightand center dash panel).Performance TestsFollowing is a brief description of symptoms orconditions that could exist if something goeswrong with a refrigerant part.RECEIVER-DRIERThe receiver-drier is normally at outsidetemperature. To the touch, the entire length of theunit should be the same temperature. If noticeableA blockage at the inlet of the unit will cause highhead pressures; outlet blockages will cause lowhead pressures and little or no cooling.If the moisture indicator is pink or white (showingthat the system is wet), the receiver-drier issaturated with moisture and must be replaced.C O O L I N G S Y S T E MAlthough they are not physically connected, thereis a close tie between a vehicle’s air conditionerand its cooling system. Poor air conditionercooling can be the result of a problem in thecooling system.If the cooling system does not work correctly, theheat of the engine will rise to abnormal levels. Theadded heat will transfer to the air conditioner,other underhood parts, and maybe make its wayinto the cab. The added heat makes it necessaryfor the air conditioner to work harder and at thesame time, it reduces the air conditioner’s abilityto cool down the air in the cab. Also, if the waterregulating valve isn’t closing all the way, heat willenter the cab, giving the impression that the airconditioning system is not working.Refer to the engine cooling section for coolingsystem troubleshooting.EXPANSION VALVEProblems that start in the expansion valve showup as follows: when stuck closed, the evaporatorcoil and the expansion valve will be at outsidetemperature; when stuck open, both the coil andthe valve will be extremely cold with frost or icebuild-up.Because the expansion valve channels are verysmall, blockages in the system tend to be foundhere (the valve is very sensitive to contamination).Usually, the contaminant is water; less than adrop of water is all it takes to make the valveinoperative. When water reaches the valve, theextreme cold that results from the pressure dropfreezes the water, forming a block of ice in thevalve. After the system shuts down and the valvewarms up, the ice melts, and the valve operatesagain, only to freeze up when moisture returns.Change 12-28.1
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business