HVAC System

A/C Cycling Switch:

A/C Cycling Switch
The A/C cycling switch is mounted on a Schrader valve-type fitting on the side 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 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 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.

Typical Air Conditioning Pressure Sensor:

A/C Pressure Cutoff Switch
The A/C pressure cutoff switch is used to interrupt the A/C compressor operation in the event of high system discharge pressures.
^ The A/C pressure cutoff switch is mounted on a Schrader valve-type 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 cutoff switch, presses on the Schrader valve stem.
^ This allows the A/C pressure cutoff switch to monitor the compressor discharge pressure.
^ When the compressor discharge pressure rises, the switch contacts open, disengaging the A/C compressor. When the pressure drops, the contacts close to allow operation of the A/C compressor.
^ It is not necessary to discharge the refrigerant system to remove the A/C pressure cutoff switch.