VW Lupo Cabin Air Sensor Failure Fix Guide

Had similar issues on a VW Polo 2003 with the HVAC sensor system. The climate control would stop responding and no air would flow, matching your symptoms exactly. The root cause was a damaged wiring harness connecting to the AUC sensor near the cabin filter housing. These air quality sensors are known weak points in VW models from that era. The connections deteriorate over time and cause intermittent failures. Diagnosis involves testing the voltage at the sensor plug, a proper reading should be between 0.5V and 4.5V when the system is running. In my case, the readings were unstable, confirming the connection issue. The fix required replacing the wiring harness section and recalibrating the climate control module. While not a major mechanical issue, it needs proper diagnostic equipment to resolve fully. The repair itself is straightforward but accessing the components takes considerable time since the lower dash panels need removal. Would suggest having a shop with VW-specific diagnostic tools handle this, as generic scanners often miss these HVAC-related faults. The symptoms point strongly to a sensor or wiring issue rather than mechanical air flow problems.

Thanks for sharing your experience with the Polo HVAC sensor repair. Interesting that the wiring harness was the culprit, my auto recirculation has been acting up again lately so I should check those connections. Just wondering, what did the repair end up costing you in total? And has the air quality sensor stayed reliable since the fix? I might face the same repair soon and want to budget accordingly. My independent shop quoted 200€ just for diagnosis, which seemed steep compared to what others have mentioned for similar odor sensor issues in VWs.

Like promised in my earlier post, I took the car to a specialist who confirmed it was indeed the faulty wiring connection to the AUC sensor causing the air flow issues. The total repair cost was 95€, which included fixing the cable connection and testing the auto recirculation function. The air quality sensor has worked flawlessly since the repair three months ago. The cabin air sensor readings are now stable and the climate control system responds correctly. The 200€ diagnostic fee you were quoted seems excessive, especially since these sensor fault patterns are well-documented in VW models. The mechanic mentioned these air conditioning sensor issues are common and straightforward to diagnose with the right equipment. The key was having someone familiar with VW HVAC systems who could quickly pinpoint the connection problem without unnecessary parts replacement. Consider finding a shop that specializes in VW climate control systems, they should be able to diagnose and repair the issue for significantly less than 200€.

Thank you everyone for the helpful replies. Just wanted to update on my situation. Finally got the repair done last week at a different VW specialist shop I found. The issue was exactly as suggested, a damaged wire connection to the air quality sensor. They diagnosed it in about 30 minutes using their VW-specific scanner. Total cost came to 120€ including parts and labor, much more reasonable than the 200€ diagnostic fee my original shop wanted. The auto recirculation and air flow are working perfectly now. The HVAC sensor readings are stable and the odor sensor properly detects when to switch between fresh and recirculated air. Really glad I asked here before paying for expensive diagnostics. Big difference working with a shop that knows these common VW air conditioning sensor problems. They showed me the damaged wiring and explained everything clearly. Definitely learned to get a second opinion when quotes seem unusually high for standard repairs.