RS4 Battery Drain & Electrical Gremlins Need Urgent Fix

Had similar issues with my 2008 Audi S4 last winter. The symptoms match classic vehicle battery problems, but the actual issue turned out to be more complex. The battery sensor was reporting false readings, triggering multiple electrical faults across systems. The discharged battery symptoms were misleading. While the battery tested fine, the faulty sensor was causing the car to misread battery charge levels. This triggered protective modes in various electronics, leading to: * Unusual warning lights * Instrument cluster flickering * Hard starting * False low battery warnings The battery sensor replacement resolved all issues. Its a common failure point in these models as they age. The sensor monitors charging state and helps regulate power distribution. When it fails, it can mimic a dead battery while causing wider electrical system chaos. Worth getting the battery sensor specifically tested before replacing the battery itself. The repair required specialized diagnostic equipment to properly identify the failed sensor versus a standard battery issue. This was not a quick fix as accessing the sensor required partial removal of intake components. While not catastrophic, this issue needs proper attention since it affects multiple vehicle systems and can leave you stranded if ignored.

Thanks for sharing your experience. I went through something very similar with my RS4 recently. After dealing with battery drain and flickering dash lights, I was convinced I just needed a new battery. Turns out the battery terminals were corroded and the alternator was failing to properly charge the battery. Before replacing the whole battery, they tested the charging system and found the real culprit. Since getting it fixed, all the electrical gremlins disappeared and the car starts perfectly every time. How much did your sensor repair end up costing? Has everything been working properly since the fix? Would be good to know in case I run into similar issues down the road.

Been a few months since getting the battery sensor replaced and everything is working perfectly now. The heavily discharged battery warnings completely disappeared after the fix. The repair bill came to 315 Euro total, including diagnostic time and labor to access the sensor location. The mechanic confirmed the battery charging system is now functioning correctly, with proper voltage readings and no more false signals. While it was a bit pricey, it was worth fixing the root cause rather than just replacing the battery. No more unusual electrical issues or warning lights since then. Good call on checking your battery terminals and charging system first. Its often the connection points or charging components causing these symptoms rather than the battery itself.

Appreciate the follow-up info. After seeing your experience, I decided to take my RS4 to a specialized shop. The mechanic found multiple issues causing my electrical problems. The final repair included cleaning corroded battery terminals, replacing a worn alternator, and fixing some loose connections in the main wiring harness. The total bill came to 850 Euro, but the car runs flawlessly now. No more flickering lights or error messages. The low battery warnings completely disappeared after fixing the alternator, which wasnt properly charging the vehicle battery. Looking back, Im glad I didnt just replace the battery right away. Having a proper diagnosis saved me from throwing parts at the problem. The car starts instantly now and all electrical systems work like new.