Compressor Fitting HVAC: Description and Operation

Fig. 1 Compressor service valves, cross sectional view:

Most models are equipped with manual valves to isolate the compressor from the refrigerant system. These valves allow the compressor to be removed, or opened for oil level checks, without discharging the A/C system. Refrigerant system service access fittings are also included on most models.

During normal system operation, the manual valves are in the back-seated (fully counterclockwise) position. To isolate the compressor, the valves are rotated to the front-seated (fully clockwise) position, closing off the refrigerant line passage to the compressor. To allow refrigerant system service access, the valves are rotated to the mid-position which opens the service port while still allowing refrigerant to flow through the system. Manual compressor service valves should be in the back-seated (fully counterclockwise) position whenever service gauges are being connected or disconnected on the A/C system. Always install protective caps over manual valve stems and service ports, if equipped, after completing A/C service.