A/C Pressure Cut-Off Switch

A/C pressure cut-off switch is a dual function switch that is mounted on a Schrader valve, in discharge line, between compressor and condenser core. Switch interrupts compressor operation if high discharge pressures are sensed. See Figure. Normally closed set of contacts will open in event of high compressor head pressure, about 435-475 psi (30.6-33.4 kg/cm² ). This will cut off compressor operation to protect A/C compressor. This function helps ensure refrigerant is contained in system, helping to maintain high-side pressures, and not venting through pressure relief valve. Contacts will close if compressor head pressure drops to 220-280 psi (15.5-19.7 kg/cm² ), to restore normal compressor operation.

The switch will also open normally closed set of contacts and engage engine cooling fan in event of high compressor head pressure, about 310-340 psi (21.8-23.9 kg/cm² ). Contacts will close and engine cooling fan will disengaged is compressor head pressure drops to 240-310 psi (16.8-21.8 kg/cm² ). It is not necessary to discharge A/C system to remove pressure cut-off switch.