TM 9-4120-403-14
TABLE 4-2. UNIT TROUBLESHOOTING (cont)
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
Step 5. Check operation of compressor motor start capacitor (C4).
Step 6. Check operation of ambient air thermostat (S2).
Test thermostat. (See para 4-46.) Replace if defective. If malfunction still exists,
notify your supervisor.
3. COMPRESSOR STARTS NORMALLY, BUT CIRCUIT BREAKER SOON TRIPS.
CAUTION
Do not perform the operational check in COOL mode until input power has been supplied to the unit for at
least four hours. Liquid refrigerant tends to migrate into the compressor crankcase and cylinders during
periods when the compressor heater is not operating. Under moderate climatic conditions, the compressor
heater will normally "boil" all liquid refrigerant out within a four hour period. If the air conditioner has been
exposed to below freezing temperatures without input power, an eight hour warmup period is
recommended.
Step 1. Check that fan blades are tight and operating freely.
If not operating properly; see paras 4-55b, evaporator fan and 4-56b, condenser fan.
Step 2. Check to be sure that fan motor is running.
If not running, see malfunction 9.
Step 3. Check circuit breaker (CB)
Test circuit breaker. (See para 4-35.) Replace if defective. If malfunction still exists, notify your
supervisor.
4-17