Air Conditioning Cycling Switch

AIR CONDITIONING (A/C) CYCLING SWITCH

The A/C cycling switch is mounted on a Schrader valve-type fitting on the suction accumulator.
- The A/C Cycling switch is used by the PCM to indicate if A/C refrigerant low side pressures are within operating specifications for A/C compressor operation. A 12 volt signal is supplied by the SJB when the ignition is in the run position to the cycling switch.
- 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 12 volt signal is sent to the PCM indicating A/C refrigerant low side pressures are within operating specifications for A/C compressor operation.
- When the A/C cycling switch contacts open, the 12 volts signal to the PCM is interrupted, indicating A/C refrigerant pressures are below operating specifications for A/C compressor operation.
- 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 recover the refrigerant system to remove the A/C cycling switch.

PRESSURE TRANSDUCER

The pressure transducer is used to interrupt A/C compressor operation in the event of high system discharge pressures.
- The A/C Pressure Transducer is used by the PCM to monitor A/C refrigerant high side pressures. A 5 volt reference voltage, ground and feedback circuit is provided by the PCM to the A/C Pressure Transducer. Feedback voltage will vary in correlation to A/C refrigerant high side pressures.
- The pressure transducer is mounted on a Schrader-type valve fitting on the high pressure side of the compressor manifold and tube assembly.
- A valve depressor, located inside the threaded end of the pressure transducer, presses on the Schrader valve stem.
- This allows the pressure transducer to monitor the A/C compressor discharge pressure.
- If A/C refrigerant high side pressures reach a predetermined pressure, the PCM will enable engine cooling fan high speed operation. If pressures continue to rise, the PCM will disable A/C compressor operation via the A/C relay. Once A/C refrigerant high side pressures fall below the predetermined level, the PCM will enable the A/C compressor, (if all other A/C compressor inputs are within range, i.e. PSP, ECT, etc).
- It is not necessary to recover the refrigerant system to remove the pressure transducer.