How Does A Faulty Pressure Switch Affect Your Car's AC?


You probably know about the big components in your car's air conditioning, such as the compressor. These critical components are well-known, and their replacement costs are well-known, too. Fortunately, many air conditioning problems have root causes that are less severe than blown compressors or leaking evaporator coils.

However, some problems may initially seem to have more costly underlying problems. Your air conditioner's pressure switches are lesser-known components, but they're just as vital for your system's operation. When they fail, the symptoms may initially make you think that an expensive compressor replacement is in your future.

What Does Your Pressure Switch Do?

Your air conditioning system relies on precise refrigerant levels to function correctly. The refrigerant in any air conditioning system exists at different pressures as it moves through the system, with both a high and low side (alternately referred to as discharge and suction sides). The refrigerant will transition between vapor and liquid states as it moves between these two sides.

While phase changes are critical to the normal operation of your air conditioner, they also pose some hazards. Incorrect pressure levels can affect the temperature at the evaporator coil, preventing the refrigerant from transitioning into a vapor and allowing liquid to enter the compressor. Since a liquid is incompressible, this "slugging" can potentially damage or destroy its motor.

The pressure switch monitors for high and low-pressure thresholds, turning the compressor on or off as necessary. Incorrect pressure levels will prevent the switch from engaging the compressor or cause it to shut off prematurely, resulting in short cycling. Either way, it may seem like a problem with your car's compressor or compressor clutch.

How Do You Know If Your Pressure Switch is Bad?

While the pressure switch can cause your system to shut down if there's an actual pressure problem (such as a refrigerant restriction or leak), a faulty switch can also cause problems. You'll typically experience the same issues as a refrigerant leak or faulty compressor, including poor cooling, humid air, or a short cycling system.

You may also see a check engine light with a diagnostic trouble code (DTC) between P0530 and P0533. These codes indicate bad readings from the pressure switch, although they don't necessarily mean it is faulty. While a failing switch may trigger these codes, you can also receive them due to incorrect refrigerant pressures or electrical issues elsewhere in the vehicle.

Once you experience these symptoms, you should take your car to a qualified automotive AC repair shop as soon as possible. Although a faulty switch typically won't damage your air conditioner, frequent cycling can cause excessive wear on the compressor. Locating and fixing the problem will get your system running again and ensure you don't suffer a more expensive compressor failure.

For more information on auto AC repair, contact a professional near you.


7 October 2022

Keep Your Vehicle Safe

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