VW Fox A/C Compressor Failure: Common Causes & Fixes

I had a similar issue with a 2012 VW Polo diesel last summer and can share my experience with A/C system troubles. The symptoms matched yours exactly, no compressor engagement and complete loss of cooling. After checking the basics like refrigerant level, my workshop found the root cause was a faulty relay switch controlling power to the A/C compressor. The undervoltage condition was preventing proper activation of the system. The diagnostic process involved: Testing the pressure sensor readings, Checking the relay switch functionality, Measuring voltage at key points in the circuit, Verifying the A/C system had proper refrigerant charge Total repair cost was 240€ including parts and labor. The fix involved replacing the relay switch and recalibrating the system. Air conditioning has worked flawlessly since then. To provide more specific guidance, could you share: Any warning lights on the dashboard? Does the compressor make any noise when trying to engage? Have you noticed any refrigerant leaks under the car? What error code is the system showing? These details would help determine if your issue matches what I experienced or points to a different problem in the A/C system.

Thanks for sharing your experience. After reading through the details, my issue seems quite similar. Just had the 145000km service done last month where they did general maintenance but didnt spot any A/C problems. The AC relay check makes sense as a first diagnostic step. I have noticed a slight clicking sound when turning the air conditioning on, but the belt tensioner and A/C compressor remain completely static. No visible refrigerant leaks underneath, but I suspect there might be a slow leak somewhere since the system had been gradually losing cooling power over the past months. The error code is P0645 which points to an A/C clutch control circuit issue. Based on your experience, I will have them check the relay and electrical system first before investigating more expensive components.

Thanks for the additional details. That error code P0645 matches exactly what I encountered with my Polo before the repair. The clicking sound you describe when engaging the AC is a telltale sign of a failing relay switch, very similar to what I experienced. The gradual loss of cooling before complete failure also suggests a possible refrigerant leak working in combination with the electrical issue. My workshop found that low refrigerant pressure was contributing to the relay switch problems. The pressure switch was cutting power to protect the compressor from damage. A proper diagnosis should include: Testing the AC relay operation, Checking refrigerant pressure levels, Inspecting the pressure switch connections, Looking for any visible signs of refrigerant leaks around hose fittings The clicking without compressor engagement strongly points to an electrical control problem rather than mechanical compressor failure. This is actually good news, as relay switch replacement is much more affordable than a new compressor. Given the service history and mileage you mentioned, this is fairly typical timing for these components to need attention. The repair should cost roughly what I paid, assuming the issues are similar.

Thanks everyone for the insights. After gathering all this information about the air conditioning system, I feel much better prepared for the workshop visit. The similarities between my issue and your experience with the AC relay and pressure switch problems are quite striking. Will book the car in next week and ask them to specifically check the electrical system first, particularly the relay switch operation and refrigerant pressure levels. Hoping its just the relay and not a major compressor issue, as that would obviously be much more expensive to fix. Really helpful to know the diagnostic steps and approximate costs. Will update once I get the final diagnosis and repair completed. Makes sense now why the belt tensioner keeps moving but the AC compressor wont engage, its likely that electrical fault preventing proper operation.