Symptoms of a Bad or Failing AC Pressure Switch

The AC pressure switch is a safety switch that is mounted on both the high and low sides of the air conditioning system. It monitors the pressure of the refrigerant on its respective side of the system. There is a high side pressure switch, and low side pressure switch, and they both serve to monitor the system for pressure faults that can damage the compressor.

When the pressure is too low, the compressor risks damage due to running with low oil. When it is too high, the compressor is at risk of overheating and becoming damaged. Depending on which side of the system the sensor is mounted in, when the pressure rises too high or drops too low, the switch will turn off the compressor to prevent damage from occurring. As the pressure switches serve to protect the compressor and rest of the system from damage, they play an important role for the proper function and service life of an AC system, so they should be replaced if they are causing problems. When they begin to fail they will usually display a few symptoms that will alert the driver of a potential problem.

1. AC system cutting on and off rapidly

Repeatedly cycling on and off is part of the normal operation of an AC system. There are periods where the AC is turned off, such as when the proper temperature has been reached, and the pressure is adequate. However, if the system is cycling on and off very frequently or more rapidly than normal, it could be a sign that the cycling switch is not functioning properly.

2. Unable to cool the car

If either of the AC pressure switches fails, then the system will have a difficult time maintaining the pressure required to function properly. If the pressure is not right, then the AC system will not be able to produce the cold air required to adequately cool the cabin. You may notice that the cabin takes longer than usual to reach the correct temperature, or may not even be able to reach the correct temperature at all.

3. Compressor not coming on

As the pressure switches control the on/off function of the AC compressor, a switch failure can prevent the AC compressor from functioning at all. The compressor is what pumps refrigerant through the entire system. If it is not functioning, then the system can not operate, and will be unable to produce cold air.

Because the AC pressure switches play such a vital role in ensuring the proper operation and service life of the AC system, any problems with them should be addressed immediately to ensure the integrity of the system. If you suspect that one of your AC switches is bad or failing, have it diagnosed by a professional technician from YourMechanic. If necessary, they will be able to replace your AC pressure switch so that you can ensure the system remains functioning correctly.


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Ben

41 years of experience
1410 reviews
Ben
41 years of experience
Volkswagen Beetle L5-2.5L - Heating AC - Houston, Texas
i am well satisfied with Mr Smith working on my car(s). He replaced the Jaguar fuel pump like an expert, and then he diagnosed the VW bug ac compressor and fixed it on the spot. I would recommend him to anyone with a car issue
Nissan Altima - Heating AC - Houston, Texas
Incredibly nice and took the time to show me the problem, including comparison pictures between my unit and what a new unit should look like.

Peter

43 years of experience
1321 reviews
Peter
43 years of experience
Saab 9-3 L4-2.0L Turbo - Heating AC - Phoenix, Arizona
He knows what he's doing. Very polite and explained everything. I would no doubt use him again. I highly recommend him.
Mazda Miata - Heating AC - Peoria, Arizona
We are so thrilled to have found Peter as our new mechanic. He is very thorough and knowledgeable. He is also friendly, professional, and extremely honest. He explained to us exactly what services were needed on our vehicle to repair the air conditioner and provided us with an written estimate of the cost. He literally saved us thousands of dollars in repair costs. A local major competitor quoted us a repair cost of a minimum of $1,400 and said that the cost would go up to $2,400 if they discovered an additional part was required. Peter charged us only $202, plus performed the work at our home. The air conditioner in our 2004 Mazda Miata has honestly never worked so great--it always blew out warm air. We just assumed it was how that particular car was manufactured. We would highly recommend Peter to anyone who is in need of an experienced and honest mechanic.

Pedro

31 years of experience
78 reviews
Pedro
31 years of experience
Chrysler PT Cruiser L4-2.4L - Heating AC - Portage, Indiana
Pedro was wonderful! He was early first and foremost. He was very professional and he explained things to me. He worked quickly and was very thorough. Very happy with his service.

Manuel

32 years of experience
580 reviews
Manuel
32 years of experience
Ford Taurus V6-3.0L - Heating AC - Long Beach, California
Good guy. Knows his stuff. Knowledgeable and straightforward with diagnostics and repair costs. I’d love to work with him again! Thank you Manuel!

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