Refrigerant Pressure Sensor / Switch: Description and Operation

A/C Pressure Switch
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 ground from the PCM, and turns off the compressor.

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 climate control unit to change the speed of the condensor fan and radiator fan (High-Low).

How the Circuit Works
The climate control unit controls the blower controls, air delivery, and A/C compressor controls either automatically or semi-automatically. With the ignition switch in ON (II), battery voltage is supplied through fuse 3. The control unit is grounded at G401.