If you're having trouble with your air conditioning, the problem could be a bad AC pressure switch. The switch monitors refrigerant pressure on the high and low sides of the system and shuts the compressor off if it's below a certain threshold.
The AC pressure switch is one of two switches that protect your AC system and the compressor from being damaged. The other switch is the low-pressure cutout switch, which opens when the low-side pressure drops below a pre-determined level (usually around 25 psi).
Normally, this switch is mounted on the low side of the air conditioner's compressor. It can also be found on the high side of the unit's compressor, depending on the design.
Check for the correct refrigerant pressure in your car's AC system with the help of your air conditioning repair manual or other AC specs for the specific refrigerant gas and your ambient temperature. You should see readings near 30 psi on the low side and more than twice that in the high side when you attach the appropriate air conditioning gauge set to both sides.
If you can't get to the low-pressure switch, you should be able to locate it on a larger hose that leads from your AC compressor to the refrigerant accumulator. This hose will need to be removed and replaced with a new AC refrigerant pressure switch that you can find at your local auto parts store.
