RS4 Voltage Chaos Disrupts Multiple Systems

Had similar issues on my 2018 S5 last winter. Started with sluggish cold starts and escalated to unusual electrical failures across multiple systems. The voltage regulator turned out to be the root cause, creating power surge problems that affected various control modules. The main symptoms matched yours, multiple overvoltage codes, erratic electrical behavior, and a seemingly weak car battery. Initially, mechanics focused on just the battery, but testing revealed the voltage regulator was sending incorrect signals, causing system-wide voltage fluctuations. The fix required: Complete voltage regulator replacement, System-wide diagnostic scan, Control module resets, New battery installation (the old one was damaged by constant power fluctuations) This was a serious repair requiring specialized diagnostic equipment. The original voltage regulator had failed gradually, which explained the progressive nature of the symptoms. Without fixing the regulator, a new battery alone would have eventually faced the same issues. The complexity came from tracking down all affected systems and ensuring proper voltage regulation after the repair. Would recommend having the charging system thoroughly tested, focusing specifically on the voltage regulator output and alternator performance.

Thanks for sharing your experience! Had almost identical problems with my 2020 Audi RS4. The alternator failure led to similar symptoms, fluctuating voltage and all sorts of error messages. The voltage regulator was also compromised, causing the car ECU to receive irregular power input. Did your total repair cost stay under 1500 Euro? Also curious if youve had any circuit protection issues since the fix? My mechanics mentioned this could be a recurring problem if not addressed properly.

I can confirm my repair ended up being much more affordable than initially feared. After seeing the mechanic, the overvoltage detected was completely resolved, costing 290 Euro for addressing the heavily discharged battery issue. The technician performed a thorough system check to ensure no lingering electrical issues remained. The alternator failure symptoms havent returned since the repair. The car ECU now receives stable power, and the voltage regulator operates within normal parameters. The initial high voltage problems that caused multiple system failures are completely gone. As for circuit protection, everything has been running smoothly for several months now. No warning lights or electrical glitches have appeared. The charging system maintains consistent output, suggesting the repair addressed all underlying issues with the power distribution system. The key was having a proper diagnostic assessment that identified the root cause rather than just treating symptoms. This prevented any potential recurring electrical issues that could have damaged other components over time.

The mechanics I visited last week finally solved my electrical issues. First shop just replaced the car battery without diagnosing deeper, but problems persisted. Second mechanic did thorough testing and found the voltage regulator was failing, causing power surge problems throughout the system. Total repair came to 850 Euro including: New voltage regulator, Battery replacement, Full system diagnostic, ECU reprogramming Really relieved everything is working properly now. No more unusual warning lights or system failures. Cold starts are strong again and all electrical systems function normally. The thorough diagnosis was worth the extra time and cost compared to the first attempt at repair. Will monitor for any recurring issues but feeling confident the root cause was properly addressed. Having proper circuit protection monitoring in place now gives extra peace of mind against future electrical problems. Thanks again for the advice, helped me ask the right questions at the shop and understand what needed fixing.