Refrigerant Pressure Sensor / Switch: Description and Operation

The A/C dual pressure switch, located along the right front inner fender in the liquid pipe between the receiver/dryer and the evaporator, acts to cycle the compressor on and off under conditions of abnormally low or abnormally high refrigerant pressure.

If pressure drops below 193 kPa (28 psi) or rises above 3137 kPa (455 psi), the A/C dual pressure switch opens and signals the A/C amplifier to shut down the compressor.

Reasons for abnormally low refrigerant pressure are an insufficient refrigerant supply or very low refrigerant temperatures. Reasons for abnormally high refrigerant pressure include extremely high refrigerant temperatures or an overcharging of the system during service.