What happens when a car pressure switch fails?

[DiAdriana]

The symptoms of a failed car air conditioning pressure switch are: poor contact of the contacts or abnormal operation of the pressure switch, resulting in the compressor not working and failing to provide normal pressure protection. The car air conditioning pressure switch is an essential control component to ensure the normal operation of the car air conditioning refrigeration system. According to pressure control, it can be divided into high, medium, and low pressure; the wiring can be 2, 3, or 4 wires. The high and low pressure switches control the start and stop of the compressor when abnormal pressure occurs in the system. The following is an introduction to the content: 1. The control range of the high pressure switch is generally between 15-26 bar; 2. The low pressure switch is generally between 0-4 bar; 3. The medium pressure switch is generally 17 bar.

[LaElliot]

I remember driving for over 20 years, and during a recent trip, it was extremely hot when suddenly the air conditioning stopped cooling. The car became as stuffy as a steamer. After checking, I found out the pressure switch was broken, so the compressor wouldn't work at all, and the refrigerant couldn't circulate—no cold air whatsoever. What's more annoying is that a faulty switch can sometimes falsely trigger the system's protection, causing the engine warning light to come on. On the highway, I had to roll down the windows for ventilation, which significantly increased fuel consumption, and the gas tank emptied much faster. I hurried to the repair shop to replace the switch, and the mechanic said parts like these in older cars tend to wear out easily. He recommended annual maintenance for the AC system to prevent similar issues. That experience taught me a lesson—I now keep an emergency fan in the car for unexpected situations, or else long trips would be miserable.

[VonAmara]

I just bought a car not long ago. Last weekend when I took my child to the park, the air conditioning suddenly stopped working halfway, making my child cry from the heat. It was really frustrating. Later, when I went to the 4S store, I found out that the pressure switch was broken, causing the entire air conditioning system to shut down and preventing cold air from coming out. The mechanic explained that a faulty switch would prevent the compressor from receiving the signal to start, stopping the refrigerant flow. To make matters worse, when I tried to open the windows to cool down while driving, the outside noise was so annoying that it even affected safe driving. In the end, I spent a few hundred dollars to fix it. Now, I regularly check the air conditioning buttons and temperature settings myself to keep the system running smoothly. When such small problems arise, they not only affect comfort but also waste fuel unnecessarily. I strongly advise car owners not to ignore these issues and to address them early.

[McRyder]

I'm a car enthusiast who enjoys studying internal mechanisms. Simply put, a pressure switch acts as a safety valve to monitor refrigerant pressure. If it fails, the compressor might not respond at all, causing the AC to stop cooling. The worst-case scenario is system pressure imbalance—like a low-side leak or high-side blockage—which could damage pipelines or even cause refrigerant leaks. Driving under these conditions leads to rapidly rising cabin temperatures, affecting driving concentration. I recommend using an OBD scanner to check trouble codes first, identifying the root cause early. Don't delay repairs to avoid higher costs later.