Find the receiver/dryer canister, it should be in front of the passanger seat, just inside the engine compartment. It's a silver cylinder with a couple tubes sticking through. The pressure switch should be either attached to the receiver/dryer or to one of the tubes very close to it.
Possibly the pressure cycling switch.
This vehicle does not have a low pressure switch. It has a pressure transducer instead. The pressure transducer is located on the refrigerant line next to the alternator pulley.
It is on the acumulator.
above starter
On my service DVD i cant seem to find a low pressure switch. i did find a AC refrigerant pressure switch i dont knwo if its the same
The Refrigerant Pressure Sensor / Switch will be located just to the left of the alternator pulley on the firewall....
Above starter below Exhaust manifold
The AC low and high pressure switch is located in a housing unit near the battery. It is along the edge of the drivers side of the engine bay in a metal refrigerant line.
The A/C pressure switch is located on the driver side towards the radiator. It is installed on a tube that the refrigerant runs through on its way to the evaporator. It screws in and has a connector with 2 wires coming out of it.
Its right above the oil filter. Its easier to remove the oil filter to get to it.
in the Chevy Malibu forum
the switch is on back top of brake pedal..