What are the symptoms of a faulty air conditioning pressure switch?
3 Answers
Car air conditioning pressure switch failure manifests as: Poor contact of the contacts or abnormal operation of the pressure switch, resulting in the compressor not working or failing to provide normal pressure protection. Car air conditioning pressure switches are divided into low-pressure switches, high-pressure switches, dual-temperature switches, and three-stage pressure switches. The inspection methods for car air conditioning pressure switches are as follows: Check the continuity of the pressure switch: Use a multimeter in ohmmeter mode to measure the resistance between terminals 4M1 and 4M2 of the pressure switch. The resistance should be 0. If the resistance is not 0, it indicates poor contact of the normally closed contacts of the pressure switch, and the pressure switch needs to be replaced; if the resistance is 0, proceed with the performance check of the pressure switch. Check the performance of the pressure switch: Verify the operation of the pressure switch under specified pressure conditions. If the test results are abnormal, replace the pressure switch.
As a guy who frequently tinkers with old cars, I've seen quite a few cases where the AC pressure switch fails. Common symptoms include your AC system completely shutting down—no response when you press the buttons, just blowing air without cooling. Sometimes, the compressor acts erratically, starting and stopping repeatedly, making the AC fluctuate between hot and cold. Even more annoying is hearing the compressor click on and off repeatedly in hot weather, creating a maddening noise. This switch primarily protects the system from overpressure or underpressure. Once it fails, prolonged use can damage the compressor. Checking it isn't hard—just use a pressure gauge to measure the refrigerant and see if it's the culprit. But it's best not to force the AC on to avoid further damage. Find a reliable repair shop, because driving without AC in summer is pure misery.
Hey, my car had this same issue last year. I was driving with the AC turned on, but the air blowing out was hot, just like the heater. I tried restarting it a few times, but it didn't help—the compressor seemed dead and wouldn't kick in. The mechanic later said the pressure switch might have failed. This part controls the refrigerant pressure, and if it's broken, the compressor won't start to protect the system's safety. I noticed that sometimes the AC would blow a bit of cold air, but within minutes, it would turn hot again, as if the system was repeatedly trying and failing. If not fixed in time, the compressor could burn out, costing even more money. Now, I do regular small checks, like inspecting the refrigerant levels and ensuring the wiring connections aren't loose.
