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 TM 55-1905-219-14-8
4-5. GENERAL (Continued).
Table 4-7. Air Conditioner Erratic Operation
Troubleshooting (Continued).
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
Step 5.
Compressor discharge stop valve partially closed.
Open valve fully.
3. Compressor short cycles or low pressure cut-out.
Step 1.
Air or water flow through evaporator(s) restricted or stopped. Frosted coils or
plugged or dirty tubes.
Remove restriction to restore air or water flow. Clean coils or tubes. Defrost if iced.
Step 2.
Liquid, suction or expansion valve screens plugged.
Pump down, remove and clean screens.
Step 3.
Compressor discharge valve leaks slightly.
Test valve for leaks. If leaking, pump down, remove cylinder head, examine valve
and replace if necessary.
Step 4.
Relief valve leaks slightly.
Test valve and replace if necessary.
Step 5.
Thermal bulb on expansion valve has lost its charge.
Detach thermal bulb from suction line and hold in palm of one hand. Grip suction line
with other hand. If flooding through is observed, bulb has not lost charge. If there is
no flooding through, repair or replace with new expansion valve or power element.
Step 6.
Capacity control system set to unload at too low a suction pressure.
Adjust capacity control valve to begin unloading at a higher control point.
4-36
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