Audi A2 HVAC Vent Airflow Failure: Diagnosis Needed

The symptoms suggest a faulty air quality sensor or BMW AUC system failure. While working on my Audi A3 (2003, gasoline) last month, we discovered similar HVAC sensor issues where the ventilation stopped completely. The root cause turned out to be a disconnected wiring harness at the blower motor, not the air conditioning sensor itself. The connector had corroded and lost contact. This is a common failure point in these models when the air circulation system stops working. The repair involved cleaning the connector pins and securing the harness properly. While not a major mechanical issue, it requires removing several dashboard components to access the connection point. A proper diagnosis is important since similar symptoms can also indicate a failed blower motor or air quality sensor malfunction. The job typically takes 2-3 hours for a qualified technician to complete. This is not considered a serious repair but requires specific diagnostic equipment to verify the sensor fault codes and proper HVAC system operation after the fix. Without proper repair, the system can develop more severe issues affecting the entire climate control functionality. Getting it fixed promptly prevents additional damage to related components.

Thanks for the detailed explanation of the HVAC system issue. My auto recirculation problem ended up being quite similar, the wiring harness near the cabin air sensor was indeed damaged. Did you remember roughly how much the repair cost in your case? Also wondering if you have experienced any other climate control problems since getting it fixed? After my repair the system has been working fine for about 6 months now but noticed the air flow seems slightly weaker than before.

Just wanted to update on the repair costs since you asked, fixing the faulty cable connection near the HVAC sensor came to 95 Euro total at my regular shop. The auto recirculation feature and cabin air sensor have been working perfectly since the repair without any issues. The air quality sensor readings are now accurate and the AUC system maintains proper cabin ventilation. Unlike your situation, I have not noticed any reduction in airflow through the vents. If your airflow seems weaker, it might be worth having the mechanic check the cabin air filter or blower motor, as these can affect air volume independently of the sensor system. My repair was completed about 8 months ago and the climate control system continues to function as intended. The BMW AUC diagnostic showed all clear after they repaired the damaged wiring connection, confirming it was just the cable causing the malfunction.

After reading the helpful replies, I went ahead and got my car checked. The mechanic found the exact same wiring issue near the air quality sensor that others mentioned. The total repair cost was 120 Euro, a bit more than expected but still reasonable considering the thorough diagnostic work they did. The auto recirculation is now working perfectly again. They also discovered and cleaned a partially clogged cabin air filter, which explained the slightly reduced airflow I was experiencing. The climate control system is now functioning better than before. The entire repair took about 2 hours, and they showed me the damaged wiring harness afterward. It was clearly corroded and needed replacement. Good thing I got it fixed when I did, the mechanic mentioned it could have led to more expensive air conditioning sensor failures if left unaddressed. Thanks for helping me avoid getting overcharged this time. Having a rough idea of the repair costs and process made the shop visit much less stressful.