A/C Cycling Switch

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

Dual Function Pressure Switch
The dual function pressure switch is used to interrupt A/C compressor operation in the event of high system discharge pressures.
- The dual function pressure switch is mounted on a Schrader-type valve fitting on the condenser-to-evaporator tube.
- A valve depressor, located inside the threaded end of the dual function pressure switch, presses on the Schrader valve stem.
- This allows the dual function pressure switch to monitor the compressor discharge pressure.
- It is not necessary to recover the refrigerant to remove the dual function pressure switch.
- The dual function pressure switch has 2 sets of contacts. One electrical contact is normally closed.
- When the compressor discharge pressure rises, the switch contacts open, interrupting the 12 volt A/C request (ACCS) signal to the PCM and disengaging the A/C compressor. When the pressure drops, the contacts close, completing the 12 volt A/C request (ACCS) signal to the PCM and enabling the A/C compressor.

The switch contains a second set of electrical contacts used for high-speed fan control.
- When the compressor discharge pressure rises, the contacts close and send a 12 volt signal (ACPSW) to the PCM requesting high speed cooling fan operation. When the pressure drops, the contacts open and the 12 volt signal is interrupted.