Weak Audi Starter Despite Good Battery: Sensor Issue Alert

Having some experience with electrical issues, I faced nearly identical symptoms with my 2007 A4 2.0T. The battery testing showed normal charge levels, yet the starter behavior and dim lights were concerning. After proper diagnosis at the workshop, they identified a faulty voltage sensor disrupting the proper reading of battery levels. The voltage sensor replacement cost me 315 Euro including labor, but it completely resolved the starting issues and electrical fluctuations. The workshop ran a comprehensive battery maintenance check before replacing the sensor to ensure no other components were affected. They explained that a bad voltage sensor can mislead the car's computer about actual battery status, causing these symptoms even with a healthy battery. To help diagnose your case more accurately, could you share: Current battery age, Any recent electrical modifications, Check engine light status, Whether these symptoms occur more frequently in cold weather, If you notice any other electrical irregularities This information would help determine if your A3 is experiencing the same voltage sensor issue I encountered.

Thanks for the detailed reply about the voltage sensor diagnosis. My A3 has just completed its service at 23569 KM and the battery is relatively new, installed just 8 months ago. The check engine light remains off, but I have noticed these symptoms occur regardless of temperature. The only electrical irregularity worth mentioning is that the radio occasionally resets itself while driving. Based on your experience with the voltage sensor, this might indeed point to a similar issue. Will have the battery charge thoroughly tested again before proceeding with the sensor replacement.

Thanks for providing those additional details. The radio reset issue you mentioned actually strengthens the voltage sensor theory, as I experienced the same unusual radio resets before replacing the sensor in my A4. Even with a new battery, a faulty battery sensor can cause these symptoms because it incorrectly reports battery health to the vehicle's systems. In my case, the workshop confirmed this by monitoring voltage fluctuations during different operating conditions. One quick test you can try: check if the battery voltage reading on your dashboard or diagnostic tool fluctuates unusually while the engine is running at steady RPM. My voltage readings were erratic before the sensor replacement, jumping between values even at idle. Given that your battery is only 8 months old and these issues persist regardless of temperature, I strongly suspect your voltage sensor is showing the same behavior mine did. The battery charge testing is a good next step, but based on the matching symptoms, especially the radio resets, I would prepare for a sensor replacement. The complete fix on my A4, including battery testing and sensor replacement, resolved all electrical irregularities and restored normal starting performance. No issues have returned in the 14 months since the repair.

Thanks for sharing those points. The radio reset situation definitely aligns with what happens in cases of voltage sensor issues. My new battery being just 8 months old makes me more confident the voltage sensor is likely the culprit here. The unusual radio resets while driving, combined with the starting issues and dim lights, match the symptoms of a failing voltage sensor rather than low battery voltage. This makes sense since the battery tests show proper charge levels. Monitoring the voltage fluctuations during operation sounds like a smart diagnostic step. I will have the workshop check this specifically when testing the battery charge again. If the readings show inconsistent battery voltage levels at steady RPM, that would confirm the sensor problem. Considering your successful repair experience and the matching symptoms, especially with electrical irregularities persisting regardless of temperature, I think proceeding with voltage sensor diagnostics is the right path. The 315 Euro repair cost seems reasonable if it resolves all these issues like it did in your case. Will schedule the comprehensive testing soon and update once I have more information about the battery health and sensor readings. Thanks for helping narrow down the likely cause.