Audi A5 Blower Failure Linked to AUC Sensor Issue

Having dealt with a similar issue on my A4 2.0 TDI from 2013, I can share some relevant experience. The auto recirculation system and climate control issues are often connected through the cabin air sensor network. In my case, the air conditioning sensor system showed similar symptoms, first the AUC fault, then complete blower failure. After initial diagnosis, the workshop found that the cable connection to the odor sensor was damaged, causing the climate control system to malfunction. The repair involved: Testing the auto recirculation components, Checking all cable connections, Replacing a damaged wiring connector, Recalibrating the cabin air sensor Total cost was 95 Euro for parts and labor. The fix completely resolved both the blower issue and the AUC warning. To provide more specific advice for your case, could you share: Has the check engine light come on? Are there any unusual sounds when trying to change fan speeds? Have you noticed any other electrical issues recently? When was the last time the cabin air filter was changed? These details would help determine if your issue matches what I experienced or if it might be something different.

Thanks for checking my earlier post. Last service was done at 132770 KM and the HVAC sensor diagnostic showed multiple faults. Interestingly, the issue seems worse when the outside temperature rises. The AUC sensor and odor sensor warnings now appear intermittently, which wasnt happening before. The auto recirculation system completely shuts down right after these warnings show up. Called the workshop and they suggested replacing the entire air conditioning sensor unit, quoted 450 Euro for parts and labor. Wondering if anyone had success with a less expensive fix?

Based on your updated information, the temperature-dependent symptoms actually point to a different root cause than what I initially experienced with my A4. While I first thought it was just the wiring connector like in my case, these intermittent AUC sensor and odor sensor warnings combined with temperature sensitivity suggest a more complex issue with the climate control module itself. After getting my initial repair done, I actually faced similar intermittent warnings a few months later. Instead of replacing the entire air conditioning sensor unit as suggested by the workshop, the actual fix turned out to be much simpler. The sensor fault was caused by corroded contacts in the climate control module connector. A thorough cleaning of the connector pins and applying electronic contact cleaner fixed the issue for about 185 Euro, significantly less than the quoted sensor unit replacement. The auto recirculation system has worked flawlessly since then, with no temperature-related issues or sensor warnings. Given the similarity of our symptoms, especially the connection to outside temperature, you might want to have the workshop check the module connections before committing to a full sensor replacement. The multiple faults in your diagnostic report could be triggered by poor electrical contact rather than actual sensor failure.

Thanks everyone for the detailed responses. After reading through the suggestions, I investigated further and found some interesting developments. The workshop did a more thorough diagnostic scan today and found corrosion on the climate control module connectors, similar to what was described. They are suggesting a complete cleaning and reconnection of the components rather than replacing the entire sensor unit. The auto recirculation warnings still appear occasionally, but they confirmed the air quality sensor itself is functioning correctly when tested independently. The temperature sensitivity seems to be directly related to the corroded connections expanding in heat. They quoted 210 Euro for the cleaning service and recalibration, which sounds much more reasonable than the 450 Euro sensor replacement originally suggested. Will schedule the repair next week and update on whether this resolves both the AUC sensor fault and blower issues. Hopefully this helps others facing similar climate control problems in their vehicles.