Liquid slugging in the compressor
-Causes Broken reeds, rods, or crankshaft, Loose or broken discharge bolts

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 primarily the result of off cycle refrigerant migration on refrigerant cooled compressors and flood back on air cooled compressors.

Correction:
1) Maintain proper compressor and evaporator superheat.
2) Prevent uncontrolled liquid return (particularly oil) with accumulators.
3) Locate compressors warm ambient or install pump down cycle. 
4) Correct abnormal low load conditions.

Liquid Washout
- Worn rods and bearings, worn pistons and cylinders on lower end, worn crankshaft and oil pump, scored cover bearing and crankshaft

This is a result of refrigerant washing oil off wearing surfaces. Off cycle migration of saturated refrigerant into crankcase. Compressor starts up resulting in a mass of foam which when pumped washes bearings surfaces clear of oil film necessary for proper lubrication. Severe migration results in slugging.

Correction:
1) Locate compressor in warm ambient or install pump down cycle.
2) Check crankcase heater operation.

Liquid Dilution
Rotor drag/shortened stator, Worn bearings, Scored and/or broken rods, Scored Crankshaft worn oil pump

This is a result of liquid refrigerant returning to the compressor during running cycle. Oil becomes diluted and lubrication for oil pump and end bearing may be adequate, but as it progresses down the crankshaft insufficient oil to lubricate the rods and main bearings will occur. This may allow the rotor to drag on the stator and short out the stator.

Correction:
1) Maintain proper compressor and evaporator superheat.
2) Prevent uncontrolled liquid return with accumulator if necessary.
3) Correct abnormal low load conditions.
4) Check for defrost cycle
5) Check for oversized TXV.

High Discharge Temperature.
Discolored valve plate (cannot rub off) Overheated or burned valve reeds, Worn rings and pistons, Worn cylinders, Scored rods, bearings and crankshaft, Spot burn in stator

This is a result of temperatures in the compressor head and cylinders becoming so hot that the oil loses its ability to lubricate.

Correction:
1) High compression ratio: check for low suction and high discharge pressures. Low load and evaporator problems.
2) Check low pressure control setting.
3)Check for dirty condenser, inoperative condenser fan and ambient temperature.
4) Check air flow across compressor.

Lack of oil
Scored bearings, Broken Rods Scored crankshaft and 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 operation.
2) Check pipe sizing and also for oil traps.
3) Check for inadequate defrost.
4) Correct abnormal low load conditions.
5) Eliminate short cycling.

Electrical

Many motors fail as a result of a mechanical or lubrication failure. Many fail due to malfunctioning external electrical components.

General Or Uniform Burn

Entire  winding is uniformly overheated or burned.

Check for:
1) Low voltage.
2) Rapid cycling of compressor.
3) Inadequate motor cooling
4) Unbalanced voltage.

Single Phase Burn
Two phases of a three phase motor overheated or burned.

A result of not having current through the unburned phase and overloading the other two phases.

Correction:
1) Replace contactor.
2) Check terminal connections on compressor.
3) Check for balanced voltage.
4) Check for blown fuses.

Half Winding Single Phase Burn.

This shows as when one half of the motor has a single phasing condition on a part wind motor with a two contactor system.

Correction
1) Check both contactors as one may be defective.
2) Check timer for proper time delay.

Start Winding Burn

Only the start winding is burned in a single phase compressor due to the excessive current flowing through the start winding.

Correction:
1) Check common, start, and the run wiring.
2) Check the start capacitor and/or the start relay.
3) Check for compressor overloading.

Run Winding Burn

Only the run winding is burned in a single phase compressor.

Correction:
1) Check relay.
2) Check run capacitors