Audi RS3 Defroster Failure: Quick Fix Guide Needed

Had the same problem on my 2015 Audi S3 2.0 TFSI. The window demister and rear defroster failure turned out to be connected to a failing battery. When the battery charge drops too low, the car starts shutting down non-essential systems, including window heating elements. The initial symptoms were similar, both front and rear window defrost stopped working properly. The battery diagnostic showed it was heavily discharged and could no longer hold proper charge. This is actually a common issue on VAG cars with high mileage. The fix required: Full battery replacement, Electronic control module reset, Testing of all heating elements After replacement, all window heater functions returned to normal operation. The car defrost system needs consistent voltage to operate the heating elements effectively. This was a serious repair since a failing battery can eventually prevent the car from starting and damage other electrical components. Worth getting the battery tested first before exploring more complex defroster repairs. Most auto parts stores offer free battery testing services. Tip: If your battery is original from 2018, its likely due for replacement based on typical 4-5 year battery lifespan.

Thanks for the detailed reply about the battery being the root cause. Very helpful. My RS3 is actually still at the shop now. The thermal window system and auto defrost were definitely the initial symptoms, just like you described. They also found the battery was heavily discharged when testing. Did your heating coil system continue working properly after the battery fix? And if you remember, what was the total cost for the battery replacement and reset work? Just trying to budget for what I might be looking at for the defroster repair.

After getting it fixed at the shop, all the window heater functions have worked perfectly for over a year now. The thermal window system and auto defrost operate just like new. The battery replacement completely resolved the heating coil issues, no problems since then. The total repair cost was 290 Euro, which covered the new battery, electronic reset, and full testing of the window demister system. Looking back, it was worth every cent since a failing battery can lead to much more expensive electrical problems if left unchecked. The window heater functions need proper voltage to work correctly, so once the battery issue was sorted, everything returned to normal operation. Regular battery maintenance has kept the defrost system working reliably since the repair. A properly functioning battery really is crucial for these modern cars with complex electrical systems. When the car defrost started working again, it confirmed the mechanic had diagnosed the root cause correctly.

Since having it repaired at the shop last week, really pleased with the outcome. The rear defroster and auto defrost are both working perfectly again. My final bill came to 310 Euro, slightly more than expected but worth it considering the alternative of more serious electrical issues. The mechanic confirmed the thermal window system failure was definitely caused by the discharged battery. They did a complete electrical diagnostic, replaced the battery, and reset all systems. The window demister now works instantly when activated, actually better than it did before. Best part is I got out cheaper than expected since no heating coil replacement was needed. The battery was the culprit all along. Glad I addressed it before winter when I really need those defrosters working properly.