Multiple Electrical Issues on Audi, Battery Draining Fast

Having faced an identical battery drain issue with my 2006 S6, I can share my experience as someone with moderate car repair knowledge. The symptoms matched exactly, weak starts, error messages, and a discharged battery that kept losing charge even after recharging. After multiple attempts at charging the battery, the problems persisted. The workshop diagnosed a faulty battery sensor, which was incorrectly reporting battery status to the vehicle management system. This caused irregular charging patterns and eventually led to the battery drain issues. The repair, including diagnostics and parts replacement, cost 315 Euro. Since your symptoms align closely with what I experienced, it could be the same underlying issue. However, to provide more specific guidance: What exactly are the error messages showing? Have you noticed if the battery drains even when the car sits unused? Did you get specific voltage readings from the battery test? The battery sensor malfunction can be tricky to diagnose without proper testing equipment, as it mimics symptoms of a failing battery or alternator. Getting these details would help determine if your case matches the issues I encountered.

Last service done 3 months ago at 85712 KM. The battery failure symptoms you described match exactly what I experienced. After the electrical system scan, the workshop found my alternator was undercharging the battery, leading to a constant low battery state. When they checked the charging circuit, the voltage regulator inside the alternator had failed. A replacement alternator plus labor came to 450 Euro, and this fixed all the electrical gremlins. No dead battery issues since then. The vehicle battery now maintains proper charge and all systems work normally. The alternator should be properly tested before assuming its just a battery problem, especially with these multiple symptoms showing up together.

Thanks for the update on your S4 repair. These electrical issues can really snowball, my S6 showed nearly identical symptoms before I discovered the battery sensor problem. Its interesting how similar electrical problems can have different root causes. In your case, the faulty alternator voltage regulator was preventing proper battery charging. My battery sensor issue caused similar symptoms but through incorrect charge monitoring. This really highlights why proper diagnostic testing is crucial with electrical system problems. What looks like a simple dead battery can actually stem from multiple components, alternator, voltage regulator, sensors, or the battery terminals themselves. Good point about thoroughly testing the charging system. A vehicle battery test alone might show discharge, but wont reveal if the alternator is the underlying cause. The comprehensive diagnosis saved you from repeatedly replacing parts unnecessarily. Glad to hear the new alternator resolved all the issues. The cost seems reasonable given the complete fix of the electrical gremlins. Keep monitoring your battery voltage for a while just to be sure the charging system stays stable.

Based on both our experiences, I see why thorough electrical diagnosis is critical. The symptoms were identical, yet your alternator issue and my battery sensor problem required different fixes. My S4 is running perfectly after the alternator replacement, no more weak starts or error messages. The repair cost of 450 Euro was worth it since it fixed all the electrical problems at once. The workshop did the right thing by testing the entire charging system instead of just assuming a discharged battery was the only issue. Really glad I didnt waste money replacing the car battery when the real problem was the alternator voltage regulator not charging it properly. For anyone else seeing multiple electrical issues and a dead battery, make sure to get the alternator and charging system properly tested. A vehicle battery test alone wont show if the alternator is failing to charge it correctly. These electrical gremlins can be tricky, but proper diagnosis saves money and fixes the root cause.