When the evaporator coil becomes inefficient disabling the refrigerant to absorb sufficient heat from the room air, the refrigerant does not get vaporized. This can also be caused by dirty filters. The refrigerant in liquid form reaches the compressor. It also gets mixed with the lubricating oil. Liquid refrigerant tends to ping and degrade the compressor motor insulation in due course, resulting in a motor failure. It can push the compressor oil out of the compressor and into the system resulting in a lubrication breakdown. The compressor in such cases will malfunction or stop completely within days. Liquid refrigerant in more severe cases can cause the connecting rods and crankshaft to break into pieces.
A compressor burn out is usually caused by poor maintenance or an electrical event such as a power surge. However formation of acids in the system due to chemical reaction between moisture that enters it and the various components and lubricating oil present in the system can also cause a burnout. Eventually, these acids eat away at the compressor and system parts. If this has been the cause of burned compressor, then it is not enough just to replace the damaged unit. The technician has to ensure that acids have been completely eliminated from the system through clean-ups. They usually use liquid and suction line filter dryers to drain away the last bit of acid in the unit. In case of severe burn- out, the liquid line dryer should be replaced. It is also wise to install a suction accumulator that protects the compressor from flooding in the event of a faulty evaporator.
A technician should always diagnose the cause of compressor failure. Determining the cause will tell him whether the compressor needs replacing or replacing just part of it will resolve the problem. It is faster an inexpensive to replace a valve plate than it is to replace an entire compressor.