A3 Alternator Warning Signs, Check Before You Replace

Having some experience with car electronics, I dealt with almost identical charging system symptoms on my 2013 A4 last year. The voltage drop issues and warning lights matched your description exactly, dim headlights, difficult starts, and multiple electrical errors. Initially thought it might be just the battery, but after proper diagnosis, the workshop confirmed a defective generator (alternator). The battery was actually damaged due to receiving inconsistent charging. In my case, both components needed replacement. The total repair came to 960 Euro, which included labor and parts. The car has been running perfectly since, with stable voltage readings and no more warning lights. Before jumping to conclusions, could you share: Current battery age, Voltage readings while engine running vs off, Whether the car won't start more often when hot or cold, Any recent electrical upgrades or modifications These details would help determine if you are facing the same underlying issue. A proper voltage drop test across the charging system components would also help pinpoint whether its truly the alternator or perhaps something else in the circuit.

Last service was at 53000 KM. Just had voltage tested at idle, reading 11.8V with engine running and drops to 10.9V under load. Battery is only 8 months old. The starter motor cranks slower each time, especially after short trips. No electrical upgrades or modifications installed. The battery low warning appears more frequently during cold starts. My alternator belt looks a bit worn too. Really hoping its not both the alternator and battery needing replacement, but the symptoms match what you described. Probably best to have it properly diagnosed rather than risk getting stranded with a complete electrical failure. Thanks for sharing your repair costs, helps with budgeting for what might be coming.

Thanks for those voltage readings, they definitely confirm what we are dealing with here. Those numbers point to a failing alternator, as healthy charging systems should maintain around 13.8-14.4V while running. The voltage drop under load matches my experience exactly before I had my alternator replaced. The fact that your battery is relatively new but showing signs of voltage issues strongly suggests the alternator is not properly charging it. The slow cranking starter motor and flickering lights are classic signs of alternator failure causing a system-wide voltage drop. Since your belt looks worn, have it replaced along with the alternator, a failing belt can cause similar engine misfire symptoms and electrical system problems. In my repair, they found the old belt had actually contributed to the alternator bearing wear. Based on identical issues with my A4, I would bet you are looking at a full alternator replacement. The good news is that replacing it should resolve all the electrical gremlins you are experiencing. Just make sure they test the battery capacity after fixing the alternator, sometimes they can recover once they receive proper charging again. Would recommend getting it addressed soon before you experience complete charging system failure. Keep in mind prices may have changed since my repair last year.

Thanks for the detailed readings and info. Just had mine checked by a local mechanic, and yeah, looking at a full alternator replacement. The voltage readings match yours exactly, and he confirmed the car won't start reliably much longer with these numbers. Pretty sure the failing alternator is slowly killing my new battery too. Going to book it in next week for the repair. The belt definitely needs changing at the same time since its showing wear. At least now I know what to expect cost-wise after your experience. Better to fix it properly than risk being stuck somewhere when the charging system completely fails. Will update once its sorted in case anyone else runs into similar alternator issues. Really helpful to hear from someone who went through the exact same electrical problems and got them resolved. Just hoping my battery can be saved once it starts getting proper voltage again.