Refrigerant Pressure Sensor / Switch: Description and Operation

A/C Pressure Switch

The A/C pressure switch consists of a High-Low pressure switch (A/C pressure switch A) and a Middle pressure switch (A/C pressure switch B).




High-Low pressure switch
If the refrigerant pressure becomes too high (due to blockage), or too low (due to leakage), the A/C pressure switch sends a signal to the PCM to prevent the compressor from operating.




Middle pressure switch
If the refrigerant pressure goes above or below 1,520 kpa (15.5 kgf/sq.cm, 220 psi), the A/C pressure switch sends a signal to the heater control panel or the climate control unit to change the speed of the condensor fan and radiator fan (High-Low).


How the Circuit Works
The A/C pressure switch is located in the condenser outlet line where refrigerant is in a high temperature, high pressure liquid state. The switch will sense abnormally high or low pressure, and open the circuit. This removes the ground signal from the PCM, and turns off the compressor.