Econoline E550 V8-7.3L DSL Turbo VIN F (2002)
Refrigerant Pressure Sensor / Switch: Description and Operation
A/C Cycling Switch and Pressure Cutoff Switch
A/C Cycling Switch
The A/C cycling switch is mounted on a Schrader valve-type fitting on the top of the suction accumulator/drier.
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A valve depressor, located inside the threaded end of the A/C cycling switch, presses in on the Schrader valve stem.
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This allows the suction pressure inside the suction accumulator/drier to control the operation of the A/C cycling switch.
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The electrical switch contacts open when the suction pressure drops. The contacts close when the suction pressure rises.
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When the A/C cycling switch contacts close, the A/C compressor clutch field coil is energized.
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When the A/C cycling switch contacts open, the A/C compressor clutch field coil is de-energized and A/C compressor operation stops.
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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.
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This prevents icing of the evaporator core and blockage of airflow.
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It is not necessary to discharge the refrigerant system to remove the A/C cycling switch.
Pressure Cutoff Switch
The pressure cutoff switch is used to interrupt A/C compressor operation in the event of high system discharge pressures.
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The pressure cutoff switch is mounted on a Schrader valve-type fitting on the high pressure side.
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A valve depressor, located inside the threaded end of the pressure cutoff switch, presses on the Schrader valve stem.
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This allows the pressure cutoff switch to monitor the compressor discharge pressure.
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When the A/C 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.
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It is not necessary to discharge the refrigerant system to remove the pressure cutoff switch.