Liberty 4WD L4-2.4L DOHC VIN 1 (2005)
High Pressure Sensor / Switch: Description and Operation
The A/C high pressure switch controls both A/C compressor clutch engagement/disengagement, and electric cooling fan operation when equipped with
the 2.8L diesel engine. The A/C high pressure switch is mounted on a fitting located on the A/C discharge line near the A/C compressor. The A/C high
pressure switch turns off the A/C compressor if the refrigerant system pressure exceeds 3100 - 3375 kPa (450 - 490 psi).
The fitting for the A/C high pressure switch on the A/C discharge line is equipped with an 0-ring seal and contains a Schrader-type valve, which allows
the switch to be serviced without discharging the refrigerant system.
The A/C high pressure switch is connected in series electrically with the A/C low pressure switch between ground and the engine control module (ECM).
The contacts in the A/C high pressure switch open and close causing the ECM to turn the A/C compressor clutch on and off. This prevents A/C
compressor operation when the discharge line pressure approaches high levels, and also reduces electrical surging from A/C clutch engagement.
The A/C high pressure switch controls the electric cooling fan operation by monitoring refrigerant line pressures. When the A/C discharge line pressure
rises above 1900 to 2200 kPa (280 to 320 psi) the fan will turn on. The cooling fan will turn off when the A/C discharge line pressure drops to 1600
kPa (235 psi).
The A/C high pressure switch contacts open when the A/C discharge line pressure rises above 3100 to 3375 kPa (450 to 490 psi). The A/C high
pressure switch contacts close when the A/C discharge line pressure drops to 1860 to 2275 kPa (270 to 330 psi).
The A/C high pressure switch is factory-calibrated and cannot be adjusted or repaired. If the A/C high pressure switch is faulty or damaged, it must be
replaced.
