Audi TT Electrical Chaos: Bad Alternator Warning Signs

I dealt with nearly identical battery voltage issues on my 2019 Audi TTS. As someone with moderate car repair experience, these symptoms immediately pointed to electrical problems in the charging system. After seeing similar warning signs, difficult starts, flickering lights, and system malfunctions, I took it to a certified workshop. The diagnostic tests revealed a heavily discharged battery that was no longer holding proper charge. The alternator was actually fine, but the battery had degraded prematurely due to many short trips and infrequent charging cycles. The complete fix, including a new high-performance battery and system diagnostics, cost me 290 Euro. Since the repair, all electrical issues have completely resolved and the car starts perfectly every time. To help diagnose your specific case better, could you share: How many miles/kilometers are on your TT? What is your typical driving pattern (short trips vs longer drives)? Have you had any recent electrical upgrades or accessories installed? When was the last time the battery was replaced? This information would help determine if your battery health issues stem from similar root causes or if there might be other factors affecting your power supply system.

Thanks for sharing those details. My TT has 155907 KM on the clock, and I just had the regular service done last month. After checking the battery terminals today, I noticed significant corrosion buildup around the positive connection. This could explain the voltage regulator warnings and starting problems mentioned earlier. Going to clean the terminals first before considering more extensive repairs, since poor connections can mimic more serious electrical problems. Will update once I know if this fixes the issues.

Since you mentioned checking the battery terminals, that corrosion buildup is definitely a red flag and likely contributing to your charging system issues. When I found similar corrosion on my TTS, cleaning the terminals made an immediate difference in starting performance and voltage readings. For proper cleaning, I used a wire brush and battery cleaner solution to remove all traces of corrosion, then applied dielectric grease to prevent future buildup. This simple maintenance step resolved many of my alternator issues and poor starting problems before having to replace the battery. However, if cleaning the terminals doesnt fully solve your electrical problems, consider having the voltage regulator tested. In my case, what started as corroded terminals eventually revealed deeper charging system complications that required professional diagnosis. Since your vehicle has similar mileage to what mine had, its worth monitoring the battery voltage even after cleaning. A multimeter reading below 12.6V at rest might indicate the battery itself is struggling, regardless of clean terminals. Would be interested to hear if the terminal cleaning improves your starting performance and resolves those system warnings.

The corrosion issue makes a lot of sense, thanks for the detailed cleaning advice. Just finished cleaning both battery terminals thoroughly with a wire brush and proper cleaner. The difference is noticeable already. The car started right up with no hesitation this morning, and the low voltage warnings have stopped appearing on the dashboard. Going to pick up some dielectric grease today to protect the terminals from future corrosion. Also planning to monitor the charging system voltage with a multimeter over the next few days to ensure the battery health stays stable around 12.6V. If the voltage drops or the starting issues return, I will have the voltage regulator tested as suggested. Good to know this was likely just poor electrical connections rather than a failing alternator or more serious power supply problems. Will definitely make terminal cleaning part of regular maintenance going forward. Thanks again for helping diagnose what could have been an expensive repair.