VW Eos Startup Struggles Despite Good Battery & Starter

Had the same symptoms with a 2011 VW Scirocco. After multiple start attempts, the charging system diagnostic revealed a failing alternator despite the battery testing fine initially. The key finding was an electrical fault in the wiring harness between the alternator and battery, causing inconsistent charging patterns. The voltage regulator was intermittently failing to maintain proper charge levels, especially during cold starts. This created a pattern where the car would start fine sometimes but struggle other times. The complete repair required: Testing the entire charging system circuit, Replacing damaged sections of the wiring harness, Installing a new alternator with voltage regulator, Recalibrating the power supply management system It was a serious issue that required specialized diagnostic equipment to pinpoint. Simply testing the battery or starter motor individually missed the root cause. The inconsistent symptoms are typical of charging system problems rather than just a bad battery. Worth having a shop check the alternator output and complete wiring harness, particularly the connections between major electrical components. These issues often surface around the mileage range you described.

Thanks for sharing those details about the charging system repair. That sounds exactly like what I am dealing with. Did you happen to remember the total cost for fixing everything? I want to get a rough idea before heading to the shop. Also curious if youve had any other electrical issues pop up since getting it fixed? My Eos has been acting strange with other electronics too, the power windows sometimes hesitate and the radio occasionally resets itself. Wonder if its all connected to the same short circuit problem.

After getting the complete diagnosis, my total repair bill came to 290€ to fix the heavily discharged battery situation. The mechanic traced the issue to the Terminal 30 continuous plus circuit, which was causing the irregular power supply problems. Once fixed, all those secondary electrical issues cleared up too. The power windows and radio glitches you mentioned were likely symptoms of the same electrical fault. When the ignition switch isnt getting consistent power through the wiring harness, it can cause various electronic components to behave erratically. The fuse box connections were also checked during the repair to ensure proper current flow. Since the repair, the car starts reliably every time and all electrical systems work as they should. No more mysterious resets or hesitations. If your symptoms match what I experienced, having the Terminal 30 circuit and overall charging system checked would be a good starting point. Most importantly, make sure the shop does a complete electrical system diagnostic rather than just testing individual components. The root cause often lies in the connections between parts rather than the parts themselves.

I took the car to the shop yesterday after reading about these similar experiences. The mechanic found exactly what was suspected, a faulty wiring harness causing voltage drops throughout the system. The continuous power supply was being interrupted by corroded connections near the fuse box. The total repair came to 340€, which included: New wiring harness installation, Cleaning all electrical connections, Testing the starter motor circuit, Full system diagnostic check Started the car this morning and it fired right up. The power windows work perfectly now and the radio has stopped resetting. Really glad I pushed for a complete electrical fault check instead of just accepting the previous basic battery test. Would have saved time and money if Id done this from the start. Thanks to the forum members who pointed me in the right direction with the charging system advice. Sometimes knowing what to ask the mechanic to check makes all the difference.