Compressor Failures

Compressor Failures

-.    Compressor Failures:

As you read this section, I want you to remember one thing---- 98% of all compressor failures are due to a problem with the system that causes the compressor to fail.  Compressors don’t fail without a contributing causal event. If you don’t find this problem with the system  and correct it, the replacement compressor will also soon fail.

Some of the most common contributors to compressor failure are:

1.    Dirty Evaporator or Condenser
2.    Loose Evaporator Fan Belts
3.    Improper Refrigerant Charge
4.    Misadjusted Expansion Valve
5.    Controls Out of Adjustment
6.    Worn Relays and Contactors

A compressor failure is usually diagnosed in two categories:

1.    Mechanical
2.    Electrical

Mechanical Failures are usually caused by flood back that washes the oil away or dilutes the oil to a point where excessive wearing occurs on the bearings, rods and pistons.  This means  at some point in the cycle the Super Heat reaches  0 deg F and the liquid refrigerant starts entering the compressor.  The refrigerant must pick up enough heat to boil off all liquid to a vapor state so as not to damage the compressor.  Remember, all refrigeration compressors are designed to pump only vapor not liquid refrigerant.  Another common mechanical failure is caused by slugging.  Slugging usually occurs on start up where liquid refrigerant and oil migrate collecting  in the bottom of the evaporator or in the suction line.  When the system starts up it enters the compressor damaging the rods, piston, valve plates and / or blows the gaskets.


Electrical Failures are caused by a bad supply of power to the compressor.  Look for short cycling, a bad capacitor or breaker or even a recent storm that caused a power interruption. Single phase compressors may have a bad relay or capacitor.  It is important to understand that contactors, relays and capacitors have a life span and should be replaced periodically.  Electrical failures, however, are also the end result of the two.  Mechanical failures that we discussed earlier where the rotor drags or the compressor locks up and resulting in the motor burning.

To sum up, Compressors always fail because of another problem within the system.  A good preventative maintenance program will almost always save the compressor.

                             abo bahaaeddine


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