TM 9-4120-404-14
3-13. OPERATIONAL CHECK. To perform an operational check of the air conditioning unit, do the following steps.
a. Be sure the mode selector switch is in the OFF position and air conditioner is connected to power source.
CAUTION
DO NOT perform the operational check in COOL mode until 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 power
input, an eight hour warm up period is recommended.
Before starting the air conditioner in COOL mode, make sure that the fabric
condenser cover on the back of the unit is rolled up and secured and that all
screens and guards are in place and unobstructed to avoid damage to equipment.
b. Check that the fabric cover is rolled up and secured.
c. Adjust conditioned air intake and outlet louvers to the fully open position.
d. Adjust fresh air damper to fully closed position.
e. Turn mode selector switch to VENT. Fan should start.
f. Use a paper streamer or smoke and note amount of air being discharged from conditioned air louver.
g. Open fresh air damper fully.
h. Close conditioned air intake guard louvers fully.
i. Again check air flow as in step f. above. Air flow should be approximately the same.
j. Fully open louvers in conditioned air louver and fully close fresh air damper.
k. Turn temperature control thermostat knob to fully WARM (clockwise) position and then turn mode selector switch
to HEAT. Place your hand in air flow from the conditioned air outlet grille and feel for a temperature rise. When discharge
air temperature has reached a relatively stable level, turn temperature control thermostat knob to fully COOL
(counterclockwise) position. Feel that discharge air temperature drops to ambient level.
3-17
