A/C High Pressure Switch

HIGH REFRIGERANT PRESSURE SWITCH
The high refrigerant pressure switch is located in the compressor discharge line and monitors the compressor discharge pressure. This switch acts as a safeguard to prevent refrigerant "blow-off" from the compressor pressure relief valve and disengages the compressor in the case of refrigerant pressure above 2965 kPa (430 psi). in this function it supplements the A/C high side temperature sensor.

Should pressures reach that level, the switch will open cutting off the power supply to the relay and disengage the compressor clutch. As soon as the compressor shuts "OFF", the pressures will begin to drop. When they drop to 1379 kPa (200 psi), the switch will close and allow the compressor to engage. Compressor cycling due to pressure switch cycling can occur under conditions such as high Outside temperature, high humidity, extended idle, slow vehicle speed or tailwind, and is considered normal. Should cycling occur without the above conditions, a blocked line or condenser is possible and appropriate service should be performed.