*Before replacing a new A/C compressor, it is necessary to flush the A/C system and replace a new receiver drier/accumulator, o-rings, and expansion valve/orifice tube. This practice is to remove remaining oil, UV dye or burned residues from the A/C system to prevent oil contamination or leakage. 

In case of leak stop, imitation refrigerants or severe contamination are present, flushing is not allowed and the complete system must be replaced.

Note: Some models have a receiver dryer integrated inside the condenser which cannot be removed, and have to replace a new condenser instead.

If burned residues were found in the A/C system, rubber o-rings, discharge hose, evaporator, condenser, receiver drier and expansion valve must be replaced to prevent oil contamination, leakage, and damage to the new compressor. (In case of severe
contamination flushing is not possible and all parts need to be replaced)

Flush A/C system with a flushing agent is another option, it can remove moisture and excessive/dirt compressor oil from the system. It requires nitrogen to remove the remaining flushing agent residues from the system or remove it with compressed air and evacuate the air using a vacuum pump.