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 TM 5-4110-217-14
Table 4-1. Troubleshooting - Continued
MALFUNCTION
MALFUNCTION
TEST OR INSPECTION
TEST OR INSPECTION
CORRECTIVE ACTION
CORRECTIVE ACTION
Step 2.
Check for stuck-open or leaking compressor
3.
ENGINE KNOCKS OR DEVELOPS EXCESSIVE NOISE.
valves.
Step 1. Check for loose, worn or damaged engine
Clean or replace valve plates.
parts. Overhaul engine. Repair worn or
Step 3.
Check for blown cylinder head gasket.
damaged parts.
Replace gasket.
4.
ENGINE OIL PRESSURE LOW.
Step 4.
Check for shortage of refrigerant and/or leaks.
Step 1. Check for sticky plunger on oil by-pass relief
Step 5.
Check for air in system.
valve. Remove spring and plunger with a
Purge air from system.
magnet tool. Clean plunger and spring with
Step 6.
Check for overcharge of refrigerant.
approved solvent and reinstall.
Purge excess refrigerant.
Step 2
Check for defective oil pump assembly.
Step 7
Check for partly closed receiver inlet valve.
Replace oil pump assembly.
Open valve as far as it will go.
Step 3.
Check for defective oil gage.
Step 8.
Check for incorrectly adjusted expansion
Replace oil gage.
valve.
Step 4
Inspect bearings for wrong clearings.
Adjust expansion valve to admit more
5.
EXHAUST SMOKE EXCESSIVE.
refrigerant.
Step 1
Check for defective piston rings.
Step 9.
Check for possible restriction in liquid line.
Overhaul engine.
Locate and remove restrictions.
6.
ENGINE NOISY.
Step 10.
Check to see if expansion valve is open too
Step 1
Check for damaged, broken, or worn engine parts.
far.
Overhaul engine.
Adjust expansion valve to admit less
7.
ENGINE OIL CONSUMPTION EXCESSIVE.
refrigerant.
Step 1.
Check for gasket oil leaks.
Replace valve if stuck open.
Replace gaskets.
Step 11. Check for loose expansion valve bulb.
Step 2.
Check for defective piston rings.
Tighten clamp.
Overhaul engine.
Step 12. Check for restriction in expansion valve or
8.
REFRIGERATION UNIT WILL NOT OPERATE.
liquid line.
Step 1
Check for break or short in wiring.
Locate and remove restrictions.
Trace wiring and repair.
11. NOISY OPERATION.
9.
REFRIGERATION UNIT RUNS CONTINUOUSLY.
Step 1.
Check for compressor pumping oil.
Step 1
Check for compressor valves holding open or
Drain oil to correct level.
leaking.
Step 2.
Check for unserviceable compressor bearings.
Replace compressor valve plates.
Repair or replace compressor.
Step 2.
Check for blown gasket on compressor
Step 3.
Check for unserviceable compressor valve
cylinder head.
plate.
Replace gasket.
Replace valve plate.
Step 2
Check for refrigerant shortage or leak.
Step 4
Check for loose expansion valve feeler bulb.
Repair leak and add refrigerant.
Tighten feeler bulb.
Step 4
Check for restricted discharge tube or service
Step 5.
Check to see if expansion valve is operating.
inlet
Replace expansion valve.
valve.
Step 6.
Check to see if expansion valve is stuck.
Service compressor discharge valve, tubing,
Replace expansion valve.
and receiver inlet valve.
Step 7.
Check if expansion valve is stuck shut.
Step 5
Check for air in system.
Replace expansion valve.
Purge air from system.
Step 8.
Check for moisture frozen in expansion valve.
Step 6.
Check for refrigerant overcharge.
Thaw expansion valve and replace
Purge excess refrigerant.
Step 7.
Check for fan blades not turning
Step 9.
Check for air in system.
Magnetic clutch not working.
Purge air from system.
10. REFRIGERATION UNIT OPERATES TOO LONG.
Step 10. Check for overcharge of refrigerant.
Step 1.
Check to see if expansion valve is open too
Purge excess refrigerant.
far.
Adjust expansion valve.
4-2
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