Pressure Switch (Triple Pressure Switch): Inspection

WARNING: This page is about a different car, the 2012 Subaru Forester. However, it is still accessible from the selected car via links, so may be relevant.

Connect the manifold gauge to the service valve on the high-pressure side.
Disconnect the pressure switch connector.
Start the air conditioner, and check the operating pressure of switch by turning the compressor (magnet clutch) to ON/OFF. Operation of each switch is as follows.

Fig 1: Pressure Switch (Triple Pressure Switch) Operation Graph
Courtesy of SUBARU OF AMERICA, INC.
NOTE:
- High pressure switch turns the compressor (magnet clutch) to OFF when the refrigerant pressure becomes extremely high to prevent the evaporator, air conditioner piping and expansion valve from getting damaged or frozen, etc.
- Middle pressure switch effectively controls the radiator fan output by judging high load/low load in normal range.
- The low pressure switch detects a refrigerant shortage and deactivates the compressor (magnet clutch) if the refrigerant pressure is abnormally low. (Because any further compressor operation in such a state may lead to compressor seizure)