Refrigerant Pressure Sensor / Switch: Description and Operation

A/C Cycling Switch
The A/C cycling switch is mounted on a Schrader-type valve fitting on the suction refrigerant 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 suction accumulator/drier 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. For specifications regarding operating pressure(s), refer to Specifications.
^ When the A/C cycling switch contacts close, the A/C clutch field coil is energized.
^ 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 air flow.
^ It is not necessary to discharge the refrigerant system to remove the A/C cycling switch.







A/C Pressure Transducer
The A/C pressure transducer is mounted on a Schrader-type valve fitting on the high pressure side of the A/C manifold and tube.
^ A valve depressor, located inside the threaded end of the A/C pressure transducer switch, presses on the Schrader valve stem.
^ This allows the A/C compressor discharge pressure to be monitored by the Powertrain Control Module (PCM). For specifications regarding operating pressure(s), refer to Specifications.
^ The A/C pressure transducer provides a voltage signal that is proportional to the A/C compressor discharge pressure.
^ The PCM uses this information for A/C clutch control, cooling fan control and idle speed control.
^ It is not necessary to discharge the refrigerant system to remove the A/C pressure transducer.