DESCRIPTION
The low pressure cut-off switch is located on the suction line jumper tube. The switch is screwed onto a fitting that contains a Schrader-type valve, which allows the switch to be serviced without discharging the refrigerant system. The fitting is equipped with an O-ring to seal the switch connection.
OPERATION
The low pressure cut-off switch is connected in series electrically with the high pressure cut-off switch, the heater-A/C controls, the Electronic Cycling Clutch Switch (ECCS), 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 regulates the refrigerant system pressure, ensuring a sufficient amount of refrigerant throughout the system.
The low pressure cut-off switch contacts will open when the suction pressure is about 48 to 90 kPa (7 to 13 psi) or lower. The switch contacts will close when the suction pressure rises to about 103 to 193 kPa (15 to 28 psi) or above. Lower ambient temperatures, below about -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 low pressure cut-off switch is a factory-calibrated unit. It cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.