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 top of the suction accumulator.
- 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 to control the operation of the A/C cy cling switch.
- The electrical switch contacts open when the suction pressure drops to 145 - 165 kPa (21 - 24 psi).
- The contacts close when the suction pressure rises to 200 - 317 kpa (29 - 46 psi).
- When the A/C cycling switch contacts close, the signal to energize the A/C clutch is sent to the power-train control module (PCM) which energizes the A/C relay and supplies B+ voltage to the A/C clutch field coil.
- When the A/C cycling switch contacts open, the A/C clutch field coil is de-energized and compressor operation 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.
- II is not necessary to discharge the refrigerant system to remove the A/C cycling switch.