Automotive air conditioning recharging after replacing compressor

It is not recommended but it depends on the history of the system. If the refrigerant simply leaked out over time, and the low-pressure cutoff switch prevented the compressor from pumping the system into a vacuum, it should be okay. If a part was replaced, and especially if the system was open to air for a long time, you need to pump it into a vacuum to get the moisture out that condensed from the humidity in the air. Water will boil and vaporize at 77 degrees under full vacuum, then it is easy to draw out. If it is not removed, it can combine with refrigerant to form an acid that will corrode the condenser and evaporator. The receiver/drier should be replaced too, then it can absorb a few drops of water, but if that water circulates through the system, it will freeze and block the expansion valve or orifice tube. That will stop the flow of refrigerant, and the cooling, for up to an hour, then it will melt and do the same thing each time it circulates around.

Good evening.

No, there is moisture in the system that must be boiled out by vacuuming it down.

After the compressor replacement did you replace the receiver dryer as well? It is recommended once you open the system especially after you replace a bad compressor. There may be metal from the compressor in the system.

You can rent a vacuum pump from a parts store for this procedure.

Roy