Refrigerant Pressure Sensor / Switch: Description and Operation

The A/C cycling switch is mounted on a Shrader-type fitting located on top of the suction accumulator/drier. A valve depressor, located inside the threaded end of the A/C cycling switch, presses in on the Shrader valve stem. This allows the pressure inside the suction accumulator/drier to control the A/C cycling switch.

When the contacts close, voltage is applied to the A/C clutch field coil to operate the A/C compressor. When the contacts open, the A/C clutch is de-energized and the A/C compressor stops. The A/C cycling switch will control A/C evaporator core pressure to a point where the surface temperature of the A/C evaporator core is maintained slightly above freezing. This prevents icing of the A/C evaporator core and air flow blockage.