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Compressor failure mode, symptoms and corrections
A handy reference for analysis of a failed compressor, to aid in
finding cause of failure and take corrective action. Replacement new or remanufactured compressor fail at four times the rate of original compressors indicating replacement failures are caused by system
problems
Liquid slugging
Broken reeds, rods, or crankshaft.
Loose or broken discharge bolts. Blown gaskets. Slugging is a result of trying to compress liquid in the cylinders. Liquid may be either refrigerant or oil or more likely a combination of both. Slugging is a result of primarily of refrigerant migration into the oil on the off cycle.
Correction:
1. Check pump down cycle operation.
2. Is TXV sized and operating properly?
3. Suction line sized properly?
4. Check unloading.
Liquid washout
Worn pistons and/or rings.
Cylinders worn. Scored pins. Scored and/or broken rods. Worn bearings. Scored crankshaft. This is a result of refrigerant washing oil off surfaces. Off cycle migration of saturated refrigerant into crankcase. Compressor starts up resulting in a mass of foam which when pumped washes bearing surfaces of oil film necessary for proper lubrication. Washout is a minor condition of slugging.
Correction:
1. Check TXV bulb and super heat setting.
2. Is TXV oversized?
3. Check crankcase heater on during off cycle.
Liquid dilution
Rotor drag. Worn bearings. Scored and/or broken
rods. Scored crankshaft. This is a result of liquid refrigerant returning to compressor during running cycle.
Oil becoms diluted and lubrication for oil pump and end bearing may be adequote, but as it progresses down the crankshaft insufficient oil to lubricate the rods and main bearings will occur.
Correction:
1. Check TAY bulb.
2. Check superheat setting.
3. Check defrost cycle.
High discharge temperature
Discolored valve plate ( cannot rub off. )
Overheated or burned valve reeds. Worn rings and pistons. Worn cylinders. Scored rods, bearing, and crankshaft. Spot burn in stator. This is a result of temperatures in the compressor head and cylinders becoming too hot that the oil loses its ability to lubricate.
Correction:
1. High compression rotion: check for low suction and high discharge pressures. Low load and evaporator problems.
2. Check low pressure control setting.
3. Check for dirty condeser, inoperative condenser fan and ambient temperature.
4. Check air flow across compressor.
Lack of lubricatoin
Scored bearing. Broken rods. Scored crankshaft.
Low oil in crankcase. This is a result of lack of enough oil in crankcase to properly lubricate the running gear.
Correction:
1. Check oil failure switch.
2. Check pipe sizing and also for oil traps.
3. Inadequate defrost.
4. Low load.
5. Eliminate short cycling.
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