Your car’s AC pressure switch monitors refrigerant pressure inside the air conditioning system and cycles the compressor (the part that “pumps” the refrigerant) off/on to adjust. Ultimately, the purpose of an AC pressure switch is to protect the compressor.
If pressure is too low, the AC compressor may not receive sufficient oil, and if it’s too high, it may overheat.
There are two halves to an AC system, the low-pressure side and the high—each has its own AC pressure switch. A faulty pressure switch may damage the AC compressor and halt the refrigerant flow, causing your AC to stop blowing cold air.
What are the signs of a faulty AC pressure switch?
The three most common signs include:
- AC struggles to cool the cabin/blows warm air
- AC makes excessive noise
- AC stops working or cycles off/on
This guide gives extra information on all of these symptoms. We’ll also address some commonly asked questions about AC pressure switches, including:
- How long do AC pressure switches last?
- Where is the AC pressure switch located?
- How do I test an AC pressure switch?
- Can you drive with a bad AC pressure switch?
- How much does it cost to replace an AC switch in a car?
Learn more about how a car’s AC system works in our thorough guide. Prefer a visual explanation? Check out this video from YouTube’s Ratchets and Wrenches.
Table of ContentsShow
Symptoms Of A Bad AC Pressure Switch
1. AC Struggles To Cool The Cabin/Blows Warm Air
A reliable air conditioning system should quickly cool a car’s cabin after a few minutes. But if an AC pressure switch is failing (low- or high-pressure), it can harm the AC compressor.
A defective compressor may struggle to cool the vehicle’s interior fully. You may even feel warm air blowing from the vents on sweltering days.
2. AC Makes Excessive Noise
Another inferior AC pressure switch symptom is hearing excessive noise while the air conditioner is running. Specifically, you may hear “clicking” sounds from the engine compartment and beneath the dashboard.
This stems from the compressor’s clutch not fully engaging. As the problem worsens, it may become more of a “rattling” or even “shrieking” as the pump inside the compressor free spins.
3. AC Stops Working Or Cycles Off/On
Finally, if your car’s AC cycles off and on or stops working completely, either the high- or low-side pressure switch may have malfunctioned.
You’ll notice other bad AC pressure switch symptoms first, like clicking sounds or the system struggling to keep the cabin cool. Unfortunately, if the problem gets this far, you’ll likely need to replace the compressor.
Bad AC Pressure Switch FAQ
How Long Do AC Pressure Switches Last?
AC pressure switches are rated for up to 50,000 cycles, with each cycle equal to roughly 15 to 20 minutes of air conditioning. For most drivers, this means AC pressure switches should last a vehicle’s lifetime—unless the AC is constantly running.
Where Is The AC Pressure Switch Located?
Cars have two AC pressure switches, one for the low-pressure side and one for the high-pressure side. To find your car’s AC pressure switches, follow the AC lines coming from the compressor. The smaller line leads to the low-pressure switch, while the larger line leads to the high-pressure switch.
How Do I Test An AC Pressure Switch?
Testing your car’s AC pressure switch entails plugging an OBD II code scanner into the OBD port and checking the system for error codes. Some of the most common error codes associated with a faulty AC pressure switch include P0530, P0531, P0532, P0533, P0745, P0746, P0747, P0748, and P0749.
Can You Drive With A Bad AC Pressure Switch?
Yes, you can drive a car with a faulty AC pressure switch. The compressor is the only part directly affected by the AC pressure switches. So, if a switch fails, the compressor may also, but the rest of the car will run the same as normal—albeit without AC.
How Much Does It Cost To Replace An AC Switch In A Car?
To replace an AC pressure switch, repair shops typically charge for one hour at a rate of $75 to $130. Expect to spend between $15 to $50 on components. Add parts and labor, and the total cost of replacing a faulty AC switch (low- or high-pressure side) should range from $90 to $180.
Keep Repair Costs Low By Promptly Addressing Bad AC Pressure Switch Symptoms
There are many reasons your car’s AC might be blowing tepid or hot air, and a faulty AC switch is just one of many potential causes. The only way to tell for sure is to scan the system for error codes using an OBD II tool.
If you tackle any poor AC pressure switch signs promptly, the expenses for repair should not surpass $200. However, if considerable time elapses, you might have to substitute the AC compressor, which typically costs around $800.
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