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Home >> Ford >> 2007 >> Freestar V6-4.2L VIN 2 >> Repair and Diagnosis >> Heating and Air Conditioning >> Refrigerant Pressure Sensor / Switch >> Description and Operation >> A/C Cycling Switch
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A/C Cycling Switch

Air Conditioning (A/C) Cycling Switch
The A/C cycling switch is mounted on a Schrader-type valve 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 smart junction box (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-volt 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.

A/C 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).
- It is not necessary to recover the refrigerant system to remove the pressure transducer.
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