High Pressure Sensor / Switch: Description and Operation

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 electrically connected in series 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 A/C compressor clutch on and off. This prevents compressor operation when the discharge line pressure approaches high levels.

The A/C high pressure switch contacts open when the discharge line pressure rises above 3100 to 3375 kPa (450 to 490 psi). The switch contacts close 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 which cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.