Refrigerant Pressure Sensor / Switch: Description and Operation

AIR CONDITIONING (A/C) CYCLING SWITCH

The A/C cycling switch is mounted on a Schrader valve-type fitting on the evaporator outlet line.
- 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 evaporator outlet line to control the operation of the A/C cycling switch.
- The electrical switch contacts open when the suction pressure drops. The contacts close when the suction pressure rises.
- When the A/C cycling switch contacts close, the signal to energize the A/C compressor clutch filed coil is sent to the A/C control relay.
- When the A/C cycling switch contacts open, the A/C compressor clutch field coil is de-energized and A/C compressor operation stops.
- The A/C cycling switch will control the evaporator core pressure at a point where the plate/fin surface temperature will be maintained slightly above freezing.
- This prevents icing of the evaporator core and blockage of airflow.
- It is not necessary to discharge the refrigerant system to remove the A/C cycling switch.