Main reasons why fail compressors.

The lubricating oil of the compressor, in some types of compressors it is pumped together with the refrigerant. If there is no return of this oil to the compressor, the lack of oil will cause the compressor wear quickly and may occur your crash. The lubricating oil may chemically react with the refrigerant. This occurs when the refrigerant and the oil are chemically compatible, such as the R-134a refrigerant and the mineral oil. The oil may become "thin", i.e., has a low viscosity, which can also lead to the aforementioned failure. The oil chemical reaction with the refrigerant fluid also results in the formation of acids, which in turn attack chemically (react with) various materials of the compressor such as the enamel that covers the wiring of the electric motor, rubbers, plastics and metals used in compressor body, etc. Obviously, this chemical attack wears and destroys parts that could lead to crashes. Moisture (water) may also react with refrigerants and oils, forming acids, with the consequences described above. Hence the importance of proper and effective dewatering system (obtained through the evacuation process). The refrigerant inlet liquid in the compressor can also procovar failures. If the liquid is sucked by the compressor pump can reach the suction valves, causing an erosion (called blow liquid) that eventually leads to valve breakage, making the compressor ineffective or even locking it. When the compressor is subjected to high pressure differential (difference between the suction pressure and compressor discharge pressure), it needs to spend much energy for pumping the refrigerant. When this occurs, the electric motor that drives the compressor starts to consume much more electricity, which is translated by an increase in current in the compressor. For this there is the overload protection relay: if the current compressor increases greatly, the relay switches off the compressor. However, if the relay fails, or in the case of use of an improper relay (oversized), the relay can not switch off the compressor, which can lead to electric motor burns (motor wiring overheats, the glaze shield around the wire is destroyed, and the wiring can be short circuit). When the discharge temperature of the compressor is too high, the compressor as a whole is overheated, which increases the possibility of chemical reactions between moisture, cooling and lubricating oils, and can also cause a deterioration of the electric motor materials, which may lead the burning. When the compressor is off, there may be migration of refrigerant in the liquid state, the suction line to the compressor crankcase or housing. This liquid refrigerant is mixed with the oil. This can cause the oil to lose some of their lubricity, being "fine", which, when the compressor is restarted, will eventually cause increased wear in the compressor.