VW Passat AC Failure: Common Causes and Solutions

I had a comparable issue with my 2017 VW Golf GTE Hybrid last summer. Having some experience with HVAC systems in cars, I followed a similar diagnostic path. The symptoms matched exactly, no cooling, AC system completely unresponsive. After taking it to the workshop, they found the root cause was undervoltage affecting the A/C compressor. The pressure switch and pressure sensor were getting incorrect readings due to the electrical issue. The repair involved: Complete system diagnosis, Voltage regulator replacement, Testing the belt tensioner, Recalibrating the HVAC system Total cost was 240€ including parts and labor. The fix restored full AC functionality. Before jumping to conclusions about your Passat, it would help to know: Are you getting any specific error codes? Did the issue start suddenly or gradually? Does the AC belt look intact and properly tensioned? Have you noticed any other electrical issues? These details would help determine if your issue is similar to what I experienced. The workshop mentioned these voltage-related AC failures are somewhat common in hybrid systems of that generation.

Just had the car serviced last week at 58927km. In response to the voltage questions, the AC failure was sudden with no warning signs. The belt looks fine visually and tensions correctly. Error codes point to the relay switch and A/C compressor circuit. No other electrical problems noticed. My main concern is a potential refrigerant leak since I can hear a slight hissing near the compressor area. Would testing refrigerant pressure be a good next diagnostic step before replacing components? The service technician did not specifically check the AC system during the recent maintenance.

Thanks for providing those additional details about your Passat. After dealing with my Golf GTE issue, I learned a lot about these hybrid AC systems. The hissing sound near the A/C compressor definitely warrants investigation. A refrigerant leak could explain both the sudden failure and the error codes youre seeing. In my case, even though the problem ended up being electrical, the shop did a pressure test first to rule out leaks. Having dealt with this system, I would strongly recommend: 1. Pressure testing the system to check refrigerant levels 2. Visual inspection of all AC lines and connections for signs of oil residue 3. Testing the AC relay as a relatively inexpensive first fix The pressure switch could also be triggering a false reading if theres a refrigerant leak, causing the system to shut down to protect the A/C compressor. Since your car was just serviced but the HVAC system wasnt checked, getting these basic tests done would be smart before replacing major components. Unlike my voltage issue, your symptoms point more toward a potential refrigerant leak. The service cost for a pressure test is usually around 50€ and could save spending unnecessarily on electrical parts.

Based on those suggestions, I think I'll go ahead with the pressure testing first. The hissing sound combined with the complete system shutdown does make a refrigerant leak seem likely. It makes sense that the pressure sensor would trigger a shutdown to protect the A/C compressor if refrigerant levels are too low. I already contacted a shop that can do the pressure test tomorrow for 45€. If it turns out to be just a small leak, that would be much better than having to replace the relay switch or other electrical components. Will update once I know the results from the testing and what the actual fix ends up being. Thanks for sharing your experience, even though your issue turned out to be voltage-related, your diagnostic approach helped me figure out a logical way to troubleshoot this. The pressure test seems like the right first step before diving into more complex repairs.