A/C High Pressure Switch

The A/C high pressure switch controls both A/C compressor dutch engagement/disengagement, and electric cooling fan operations when equipped with the 3.5L/3.8L diesel engine. The A/C high pressure switch is mounted on a fitting located on the 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 A/C high pressure switch fitting on the discharge line is equipped with an O-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 powertrain control module (PCM). The switch contacts open and close causing the PCM to turn the compressor clutch on and off. This prevents compressor operation when the discharge line pressure approaches high levels, and also reduces electrical surging from compressor clutch engagement.

The A/C high pressure switch controls the electric cooling fan operation by monitoring refrigerant line pressures. When the 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 discharge line pressure drops to 1600 kPa (235 psi).

The A/C high pressure switch controls the A/C clutch operation by disengaging the clutch when the discharge line pressure rises above 3100 to 3375 kPa (450 to 490 psi). The switch contacts will close and allow A/C clutch engagement when the discharge line pressure drops to 1860 to 2275 kPa (270 to 330 psi).

The A/C high pressure switch is a factory-calibrated unit. The switch cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.