A/C Low Pressure Switch: Operation

WARNING: This page is about a different car, the 2006 Dodge Viper. However, it is still accessible from the selected car via links, so may be relevant.

The A/C low pressure switch monitors the pressure of the refrigerant leaving the accumulator to the A/C compressor. The A/C low pressure switch is electrically connected in series with the A/C high pressure switch, between ground and the powertrain control module (PCM). The A/C low pressure switch contact opens or closes the path the ground, signaling the PCM to turn the A/C compressor clutch on and off. This regulates the refrigerant system pressure and controls evaporator coil temperature. Controlling the evaporator temperature prevents condensate water on the evaporator fins from freezing and obstructing A/C system air flow.

The A/C low pressure switch contacts open when the suction pressure is approximately 131 to 141 kPa (19 to 21 psi) or lower. The switch contacts close when the suction pressure rises to approximately 241 to 269 kPa (35 to 39 psi) or above. Lower ambient temperatures, below approximately -1° C (30° F), will also cause the switch contacts to open. This is due to the pressure/temperature relationship of the refrigerant in the system.

The A/C low pressure switch is factory-calibrated and cannot be adjusted or repaired. If the A/C low pressure switch is faulty or damaged, it must be replaced.