Audi Q7 Hybrid Defrost System Failure Alert

Having some experience with hybrid vehicles, I encountered a similar issue with my 2020 Audi Q8 Hybrid last winter. The rear defroster and windshield heating system completely stopped working, showing similar symptoms to what you describe. After initial troubleshooting, my workshop discovered the main hybrid battery was heavily discharged, affecting the car's electrical systems, including the window demister functions. The complete defroster repair involved testing and recharging the battery system, plus checking all heating coil connections. The total repair cost was 290 Euro. This battery discharge issue is somewhat common in hybrid models when certain conditions align. However, to provide more specific guidance for your case, could you share: 1. When did you first notice the car defrost issues? 2. Have you observed any other electrical problems? 3. What is your current mileage? 4. Are there any other warning lights on the dashboard? These details would help determine if your situation matches what I experienced or if there might be a different underlying cause.

Last service was done at 75000 KM and I first noticed these thermal window issues about 2 weeks ago. The hybrid battery shows normal charge levels, and I have no other warning lights on the dashboard. The only electrical quirk is that sometimes the rear defroster takes multiple button presses to activate. The auto defrost and window heater functions are completely unresponsive though, regardless of how many times I try. Did any of you find that a simple fuse replacement fixed similar symptoms?

Thanks for providing those details. Based on what you describe, your situation seems different from my Q8 experience, despite the similar symptoms. The multiple button presses needed for the rear window defroster suggests a possible switch or wiring issue rather than the battery discharge problem I encountered. While a blown fuse could cause heating coil failures, the fact that both your front and rear auto defrost systems are affected points to a more complex electrical issue. In my case, even with the battery problem, the switches themselves worked consistently when pressed. Given the specific symptoms you mention: Normal hybrid battery levels, Multiple button presses needed, Complete failure of auto defrost, No other electrical issues This sounds more like a potential control module issue or damaged wiring harness. When my workshop did the defroster repair, they mentioned that modern heating systems often fail due to control module problems rather than simple fuse issues. Before heading to a shop, you might want to check if the window demister functions work in extreme temperature conditions, as this could help diagnose whether its a sensor or control module problem. But based on my experience, this will likely require professional diagnostic equipment to properly identify the root cause.

Thanks for the detailed insights. After hearing about your experience and others responses, I decided to have the car checked professionally. You were right, it wasnt the same battery issue as your Q8. The diagnostic revealed a faulty control module affecting both the rear window and front auto defrost systems. The connection problem causing the multiple button presses was related to corroded contacts in the switch assembly. The total repair came to 780 Euro, quite a bit more than a simple battery fix, but at least all window demister functions are working perfectly now. The heating issue turned out to be more complex than initially thought, but getting it properly diagnosed and fixed was worth it. Better to address these car defrost problems before winter anyway. Will update the thread if any similar problems occur, but for now, all thermal window systems are functioning as they should. Thanks again for helping me narrow down the possible causes.