The A/C pressure switch protects the air conditioning system. It contains internal sensors that monitor the pressure of the refrigerant. If pressure drops too low (indicating a leak), the switch opens, cutting power to the compressor to prevent it from running dry. If pressure climbs too high (indicating a blockage or fan failure), the switch also opens to prevent hoses from bursting.
Mechanic Glossary
A C Pressure Switch
A safety switch that monitors system pressure and disengages the A/C compressor if pressure is too high or too low.
Frequently Asked Questions
The A/C compressor cycling on and off rapidly, the A/C refusing to turn on at all, or erratic cooling performance.
Most cars have two: a low-pressure switch on the suction line and a high-pressure switch on the discharge line. Some modern cars combine them into a single transducer.
You can jump the harness connector pins with a wire to see if the compressor clutch engages. Only do this for a few seconds; running the compressor without refrigerant will destroy it.