Section II. AIR CONDITIONING TROUBLESHOOTING
1 14-3. GENERAL 1
Information in this section is used by support maintenance personnel to diagnose and correct air
conditioning system malfunctions.
14-4. AIR CONDITIONING TROUBLESHOOTING INSTRUCTIONS
Before taking any action to correct a possible air conditioning malfunction, perform the following:
(1) Question vehicle operator about nature of complaint and conditions under which problem occurs.
(2) Record symptoms and compare symptoms of listed malfunctions to help identify problem.
(3) Conduct visual inspection of system to identify obvious problems (loose belt or fittings,
disconnected wires, dirty condenser, or evaporator surfaces, blown fuses, and massive leak).
14-5. INITIAL TEST CONDITIONS
a. Install manifold gauge set on compressor (para. 25-15).
b. Ensure a full charge of refrigerant is in system at start of test.
(1) Check sight glass reading for low refrigerant indication.
(2) Add refrigerant (para. 25-151, if necessary.
Gauge readings taken at normal engine idle may not accurately
reflect condition of system.
c. Set engine speed at 1,500 rpm (TM 9-2320-387-10X
d. Set air conditioner cooling and blower speed settings to maximum value (TM 9-2320-387-10).
e. Open vehicle doors to permit fresh flow of air through passenger compartment.
f. Run engine with air conditioner on for a minimum of five minutes to allow temperature and pressure
14-6. SYSTEM PERFORMANCE EVALUATION
a. Measure air temperature at outlet duct in crew compartment by inserting end of thermometer in
center air duct louver. Normal operation air temperature at duct louver is 40-50°F (4-lOC), while ambient
(air) temperature is 70°F (21°C) and humidity is low. Refer to table 14-2 for relative humidity effect on
normal operation air temperature at duct louver.
In a properly functioning system, air temperature at duct will
increase as the ambient air temperature and humidity increase.
b. Low and high side gauge readings on manifold gauge set are used to identify and diagnose system
problems. Refer to table 14-2 for normal low and high side pressure readings.
c. After troubleshooting, repair, evacuation, and recharging are complete, conduct performance test of
system. Refer to table 14-2 for performance guidelines.
d. Perform pressure gauge and in-vehicle cold air duct readings to confirm system has been restored to
peak operating condition.
e. Verify refrigerant level is correct before returning vehicle to service.