Audi SQ7 Blower Motor Failure Due to AUC Sensor Issues

Been there with my 2020 S8, which had almost identical HVAC sensor issues. I have some experience working on these luxury vehicles, particularly their climate control systems. The symptoms you describe match what I dealt with, complete blower failure despite functioning display. In my case, the cabin air sensor and air conditioning sensor wiring had connection issues. The workshop found that the plug connecting the AUC sensor was loose and had some corrosion, causing incorrect signals to the climate control unit. The fix involved cleaning the connections and securing the plug properly. Total repair cost was 95 Euro including diagnostics. Since then, no more issues with the blower motor. Before suggesting specific solutions, could you please share: Any error codes showing up? Does this happen in all climate modes? Have you noticed any unusual smells before the failure? Did you recently have any work done on the climate system? These details would help determine if your issue matches the sensor fault I experienced or if its something else in the HVAC system.

Thanks for the input. My current mileage is 124252KM and the last service was done 2 months ago. No error codes showing in any system. Auto recirculation seems completely dead regardless of mode selection. The issue persists in all climate modes, even manual settings. No unusual smells before the failure and no recent work on the climate system. The auto function typically worked flawlessly before this complete shutdown. Should also mention I tried basic troubleshooting like checking fuses and the battery terminals, all appear fine. Just seems odd that the air quality sensor could cause a total blower failure rather than just incorrect air circulation settings.

Thanks for those details. Given your mileage and symptoms, I am even more convinced we had the same issue. After my sensor fault incident with the S8, I learned these systems are quite interconnected. The air quality sensor and HVAC sensor system in these cars can indeed trigger a complete blower shutdown as a fail-safe measure. When the AUC sensor sends erratic signals, the climate control unit sometimes interprets this as a critical fault and shuts down the blower to prevent potential damage. Since you have checked fuses and battery connections, I would suggest focusing on the sensor array. On my S8, accessing the air conditioning sensor and its wiring harness required removing some trim pieces under the dash. The workshop found that despite no error codes, the sensor connections had degraded enough to cause communication issues. If your symptoms match mine exactly, check these specific points: Sensor connector pins for oxidation, Wiring harness condition near sharp edges, Ground connection quality The repair in my case was straightforward once diagnosed. Given your higher mileage compared to when I had the issue, the connection problem could be more pronounced. Might be worth having the entire HVAC sensor circuit checked while they are in there.

Appreciate the detailed suggestions. I will have the shop check the sensor connections and wiring harness. The auto recirculation failing completely along with the blower does align with what you experienced. Makes more sense now why the air quality sensor could trigger a total shutdown, never realized the BMW AUC system had this kind of fail-safe programming. Will schedule an appointment to have them specifically look at the cabin air sensor connections and ground points. Hopefully its just corroded pins or a loose connection like in your case. The fact that there are no error codes despite complete system failure seems to point toward a sensor communication issue rather than a mechanical blower problem. Will update once I get it checked out. The 95 Euro repair cost you mentioned sounds much better than replacing the entire blower motor, which was my initial worry when troubleshooting this. Thanks for sharing your experience, gave me a clear direction to investigate.