A/C Pressure Switch

The A/C cycling switch is mounted on a Schrader valve-type fitting on the top of the suction accumulator/drier.
^ A valve depressor, located inside the threaded end of the A/C cycling switch, presses in on the Schrader valve stem.
^ This allows the suction pressure inside the suction accumulator/drier to control the operation of the A/C cycling switch.
^ The electrical switch contacts open when the suction pressure drops to 152-193 kPa (22 to 28 psi).
^ The contacts close when the suction pressure rises to 276-324 kPa (40-47 psi).
^ Ambient temperature below approximately 7-10° C (45-50° F), during cold weather seasons, prevents the A/C cycling switch contacts from closing.
^ This is due to the pressure/temperature relationship of the refrigerant and the requirement of the system pressure to reach 276-324 kPa (40-47 psi) to close the A/C cycling switch contacts.
^ These contacts control the electrical circuit to the A/C clutch field coil.
^ When the A/C cycling switch contacts close, the signal to energize the A/C clutch is sent to the constant control relay module.
^ The constant control relay module then supplies the voltage to energize the A/C clutch for operation of the A/C compressor.
^ When the A/C cycling switch contacts open, the constant control relay module opens the A/C clutch electrical circuit to de-energize the A/C clutch and the operation of the A/C compressor stops.
^ The A/C cycling switch will control the A/C evaporator core pressure at a point where the plate/fin surface temperature will be maintained slightly above freezing.
^ This prevents icing of the A/C evaporator core and blockage of airflow.