E-tron Voltage Issues Damaging Critical Systems

I encountered similar electrical issues with my 2019 Q4 Sportback e-tron. With some experience working on electric vehicles, I can share my troubleshooting journey. The symptoms matched yours exactly, weak battery performance, system failures, and voltage regulation warnings. After initial self-diagnosis attempts using basic voltage testing, I took it to an EV-certified workshop since the car battery and electrical systems in these models are quite complex. The workshop diagnosed a failing voltage regulator that was causing erratic power distribution, leading to the car battery being irregularly charged. The total repair came to 290 Euro, which included: Full diagnostic scan, Voltage regulator replacement, Battery reconditioning, System reset and calibration Before I can offer more specific advice, could you share: Full diagnostic codes your system is showing, Whether this started suddenly or developed gradually, If you notice the issues more during specific conditions, Your current battery charging patterns Early intervention is crucial with alternator failure and electrical issues like these, as continued voltage fluctuations can damage sensitive car electronics throughout the system.

Latest service was at 32000 KM. After receiving your reply, I gathered the following details: The fault codes are P0AC7 and P0A7F, consistently showing when the system issues occur. Problems started gradually over 2 weeks, beginning with occasional dashboard flickering. Battery usually charges normally to 100% but drains unusually fast even when parked. The high voltage issues seem worse during cold starts, which matches your voltage regulator theory. Current symptoms also include sporadic air conditioning failure and parking sensor malfunctions, suggesting circuit protection systems might be triggering. Your repair costs seem reasonable considering the potential damage to car electronics. Will contact a certified workshop for proper diagnosis. Thanks for detailing your similar experience with overvoltage problems.

Thanks for providing those details. The fault codes and symptoms you describe match my experience almost exactly, especially the gradual onset and cold start issues on my Q4. Just to add to my previous response, after the voltage regulator repair, I discovered there was minor damage to some auxiliary systems from the power fluctuations. The workshop found the circuit protection system had been repeatedly triggering to prevent more serious electrical issues, but this constant cycling had stressed some components. With your car showing similar high voltage problems and identical fault codes, I strongly suspect the same root cause. The rapid battery drain while parked is particularly telling, this was also happening to my car due to the faulty voltage regulation causing parasitic draw on the system. A crucial point: the total repair cost I mentioned earlier ended up being 450 Euro because we also needed to replace: The main control module relay, Several blown fuses in the power distribution system, A damaged parking sensor control unit Getting this fixed promptly helped prevent more extensive damage to the car electronics. Based on the matching symptoms and fault codes, I suggest requesting a full electrical system diagnostic when you visit the workshop, not just voltage regulator testing.

Thanks everyone for the detailed responses. After reviewing all the information and checking the fault codes against the P0AC7 and P0A7F readouts more carefully, I am confident this is indeed a voltage regulator issue causing the high voltage problems. Just booked an appointment with a certified workshop for next week. They quoted 500 Euro for a complete electrical system diagnostic including circuit protection testing and voltage regulator inspection. The service advisor mentioned potential alternator failure monitoring would also be part of their assessment given the symptoms. Will update once I have the final diagnosis and repair completed. Really hoping to avoid any cascading damage to the car electronics from these overvoltage issues. The rapid battery drain and system failures are concerning enough already. Thanks again for sharing your similar experiences and repair details. It helped narrow down the likely causes and gave me a realistic cost expectation for the fixes.