Low Pressure Sensor / Switch: Description and Operation

LOSS OF CHARGE SWITCH - FRONT
This vehicle is equipped with a Loss of Charge Switch. This switch is screwed onto a fitting on the suction jumper line between the evaporator and the low side refrigerant system service port. The switch is used to measure if refrigerant system pressure goes too low. It is not responsible for cycling the A/C compressor clutch.

The loss of charge switch is connected in series electrically with the Heater-A/C controls 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 system charge is low and prevents damage to the compressor. The switch opens with a pressure of 7 to 13 psi and closes when the pressure rises to 15 to 25 psi.