Escape 2WD L4-122 2.0L DOHC VIN B Zetec SFI (2003)
Refrigerant Pressure Sensor / Switch: Description and Operation
A/C Cycling 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.
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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 to control the operation of the A/C cycling switch.
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The electrical switch contacts open when the suction pressure drops to 152-193 kPa (22-28 psi).
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The contacts close when the suction pressure rises to 276-324 kPa (40-47 psi).
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When the A/C cycling switch contacts close, the signal to energize the A/C clutch is sent to the Powertrain Control Module (PCM) which
energizes the A/C relay and supplies B+ voltage to the A/C clutch field coil.
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When the A/C cycling switch contacts open, the A/C clutch field coil is deenergized and compressor operation stops.
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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.
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This prevents icing of the A/C 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.
A/C Pressure Cut-Off Switch
The A/C pressure cut-off switch is used to interrupt A/C compressor operation in the event of high system discharge pressures.
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The A/C pressure cut-off switch is mounted on a Schrader valve-type fitting on the high pressure side of the condenser to evaporator line.
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A valve depressor, located inside the threaded end of the A/C pressure cut-off switch, is used to monitor the compressor discharge pressure.
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It is not necessary to discharge the refrigerant system to remove the A/C pressure cut-off switch.
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The A/C pressure cut-off switch has two sets of contacts. One electrical contact is normally closed.
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When the compressor discharge pressure rises to approximately 3,103 kPa (450 psi), the switch contacts open, disengaging the A/C compressor.
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When the pressure drops to approximately 1,724 kPa (250 psi), the contacts close to allow operation of the A/C compressor.
The switch contains a second set of electrical contacts used for high-speed fan control.
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When the compressor discharge pressure reaches approximately 2,241 kPa (325 psi), these contacts close and engage the high-speed fan control.
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When the pressure drops to approximately 1,896 kPa (275 psi), the contacts again open and the high speed fan control is disengaged.