Audi A4 Window Heating Failure on Both Ends

I had a comparable issue with my 2016 Audi A6 2.0T last winter and have some experience with electrical problems in these models. After checking fuses like you did, I brought it to my regular workshop since both the front and rear window heating systems failed simultaneously. The diagnosis revealed a heavily discharged battery which was causing multiple electrical system failures, including the heating coil and auto defrost functions. The technicians explained that when the battery voltage drops too low, the car disables non-essential systems to preserve power for critical functions. This commonly affects the defroster repair components first. The total repair came to 290 Euro, which covered: Battery testing and replacement, System diagnosis, Electrical system reset Before suggesting more specific solutions, could you share: Have you noticed any other electrical issues like slow starting? Does your battery warning light show on the dashboard? How old is your current battery? Are there any other error codes showing? This would help determine if your issue matches what I experienced or if you might be dealing with something different in your heating system.

My service history shows 193444 KM and this indeed seems to match my similar experience. The battery check revealed 11.8V when tested, indicating significant discharge. The window demister and auto defrost issues appeared right after I noticed delayed starting. The thermal window system worked perfectly again after the battery replacement and reset. The car defrost function on both windows now operates normally. Total cost was 320 Euro including labor and system recalibration. The heating issue can definitely be misleading, making you think the defrost elements are faulty when the root cause is often just insufficient power supply. A voltage test should be your first diagnostic step before replacing any heating components.

Thanks for sharing those details about your repair experience. It matches my case exactly, my 2016 A6 also showed similar battery voltage readings around 11.9V before replacement. The rear defroster and windshield heating issues are classic symptoms of low battery voltage in these models. The car prioritizes essential systems when voltage drops, which is why the thermal window features fail early. After my battery replacement, both the front and rear window defrosters worked flawlessly again. One extra tip from my experience: If you notice the car defrost systems acting up again, even with a new battery, check the alternator output. My mechanic mentioned that failing alternators can prevent proper battery charging, leading to similar symptoms. A proper voltage test under load can identify this. The 320 Euro repair cost seems standard, mine was 290 Euro for essentially the same work. Good call on getting the system recalibration done too, as the thermal window controls often need a reset after power issues to function correctly.

While the battery seemed the unlikely culprit at first, I am glad I shared my initial symptoms here. Having both the front auto defrost and rear defroster fail together was actually the key hint pointing to a power supply issue rather than faulty heating elements. The thermal window systems in these Audis are quite sensitive to voltage fluctuations. My 11.8V reading clearly showed why the window demister functions stopped working. The 320 Euro spent on diagnosis, battery replacement and system reset was money well spent, especially since it fixed all heating issues. For others facing similar problems: Start with a proper voltage test before assuming the worst about your defroster repair needs. In many cases, what appears as failed heating elements is just the car protecting itself from low power conditions. The quick recovery of all functions after battery replacement confirms this. Good to know this is a common pattern in these models. Will definitely check battery voltage first if any heating issues return in the future.