How do you pump down an ac compressor?

To pump down an AC compressor, first turn off the system and shut off the refrigerant supply at the service valves. Connect a vacuum pump to the service port on the low-pressure side and turn it on to evacuate the refrigerant from the system. Monitor the pressure gauge until it reaches a desired low level, typically around 20 inches of Mercury. Finally, close the service valves and turn off the vacuum pump.