RS4 Electrical Gremlins Signal Failing Auxiliary Battery

Had a similar battery malfunction in my 2019 Audi RS5. The symptoms matched exactly, weak engine start, instrument cluster errors, and general electrical system instability even after a main battery replacement. The issue was actually the voltage control module failing to properly regulate power distribution between the main and auxiliary batteries. This caused low voltage situations across multiple systems. The auxiliary battery was completely drained as a result. The fix required: Full diagnostic scan of electrical systems, Replacement of auxiliary battery, Replacement and reprogramming of voltage control module, Reset of all affected control units This was a serious repair job requiring specialized diagnostic equipment for modern Audi electrical systems. A general mechanic might miss the underlying voltage regulation problem and only replace batteries, which would not solve the root cause. Would recommend finding a shop with specific experience in modern Audi electrical systems, as these issues need proper diagnostic tools to accurately identify the failing components in the power distribution system.

Thanks for sharing those details about the RS5 electrical issues. Your case sounds very similar to what happened with my RS4 last spring. The car electronics were going haywire until the auxiliary power system was properly diagnosed. Did you happen to note the total repair cost? Also curious if you have experienced any recurring low voltage problems since getting it fixed? My mechanic warned that these electrical gremlins can sometimes come back even after a complete battery replacement and module repair.

Having my auxiliary battery malfunction fixed was definitely worth the investment. The total repair came to 290 Euro which covered diagnosing the battery failure and installing the replacement parts. Since the repair, my RS5 has been running perfectly with no sign of those frustrating electrical issues returning. The engine start is strong again and all the instrument cluster errors have completely disappeared. I think the key was having a proper diagnostic scan done to identify the exact cause of the battery not being charged correctly. It has been 8 months now without any recurring problems or voltage issues. The specialized equipment they used for testing the electrical systems really made the difference compared to basic battery checks. Having both batteries working properly again has eliminated all those concerning symptoms we were experiencing.

After hearing about your experience, I finally took my RS4 to a specialized Audi shop last week. The voltage drop issues were exactly as you described. Their diagnostic scan revealed problems with both the auxiliary power system and voltage control module. The total repair cost came to 340 Euro, slightly more than yours, but the results are impressive. The engine starts perfectly now, and all those annoying instrument cluster errors have disappeared. The car electronics are working flawlessly again. The technician used specialized testing equipment to properly diagnose the battery failure symptoms. They explained that the voltage control module was causing irregular power distribution, which explained why the previous battery replacement didnt fix the issue. Its been a week since the repair and everything is running smoothly. No more electrical gremlins. Sometimes paying more for the right expertise is worth it, lesson learned from my previous experience with the general mechanic.