What is an AC low-pressure switch?
Your car’s AC has both a low-pressure and a high-pressure switch that protect the air conditioning system compressor by monitoring the pressure. The high-pressure switch shuts off power to the compressor if the pressure is too high, while the low-pressure switch turns off power if refrigerant levels are too low.
The AC low-pressure switch looks like a small knob mounted to the compressor's upper (low pressure) side.
If the low-pressure switch stops working, the AC won’t be able to cool because the low- and high-pressure switches work together. While you can keep driving with a bad low-pressure switch, your car won’t have cool air, and you risk damaging the compressor.
When should I replace the AC low-pressure switch on my car?
A faulty low-pressure switch shares similar signs as a defective high-pressure switch, but here are common symptoms to watch out for:
AC turns on and off rapidly: A bad low-pressure switch won’t send accurate signals to the AC system, so it will switch on and off.
AC doesn’t cool your car: The AC relies on accurate pressure readings to produce cool air to circulate throughout the cabin. If the low-pressure switch isn’t functioning, the AC won’t work.
Compressor doesn’t come on: The compressor pumps refrigerant through the system, so if the low pressure switch is bad, it can damage the compressor. This is another reason why it’s so important to replace the switch as soon as possible.
Loud or strange noises: Your AC shouldn’t make unusual sounds. If you hear clicking, humming, or loud noises, get your AC inspected right away. The noises could be a sign of a faulty switch causing pressure to build up in the system.
How often should an AC low-pressure switch be replaced?
Unlike most car parts, AC pressure switch longevity is measured in cycles instead of miles or years. A new low pressure switch can last up to 50,000 cycles. This means that, in most cases, a switch will last the life of the vehicle. You only need to replace the switch if it’s faulty or damaged.
Can I replace my low-pressure AC switch myself?
If you feel confident working with your car’s electrical components, like being able to disconnect the battery, you should be able to swap out the low-pressure AC switch. It’s actually harder to diagnose if the low-pressure switch is causing the problems with AC, so don’t hesitate to get a professional inspection if you’re not completely sure that the low-pressure switch is the problem.