Refrigerant Pressure Sensor / Switch: Testing and Inspection

A/C Pressure Switch -F129-, Checking







- Ensure O-ring (10.8 mm x 1.8 mm) fits properly in groove

Functions

Switch (between the blue wires) controls the A/C clutch -N25- when pressure in refrigerant circuit is too high or if system not charged properly:
- Switch opens (compressor OFF): below 2.0 bar (29.0 psi)
- Switch closes (compressor ON): above 3.0 bar (43.5 psi)

Checking switch:

- Briefly bridge connections from terminal 1 and 2 of connector with engine running. If A/C clutch switches on -N25-, refrigerant circuit is empty.
- Closes when over 16 bar gauge pressure and opens again when under 12.5 bar gauge pressure (threshold voltage)
- R-134a pressure switch is identified with a green label or lettering "For R-134a"