VW Scirocco Electrical Issues Point to Failing Alternator

I had a very similar situation with my 2016 VW Golf TDI last winter. As someone with moderate experience working on VWs, the symptoms you describe match exactly what I encountered. After checking the battery voltage with a multimeter, which showed inconsistent readings between 10.5V and 12V, I took it to my trusted workshop. They performed a comprehensive diagnostic of the power supply system, testing both the alternator and voltage regulator. The root cause turned out to be poor battery health. The original battery had degraded significantly, causing strain on the entire electrical system. The complete diagnosis and replacement cost me 290€, including a new high-quality battery and labor. Before jumping to conclusions about the alternator, it would help to know: Is this the original battery? What voltage readings are you getting while the engine is running? Are these issues more prominent during cold weather? Have you noticed any warning lights on the dashboard? The workshop confirmed that VAG diesels from that era often show these symptoms when the battery starts failing. A battery load test would be the first recommended diagnostic step to rule out more expensive alternator issues.

Last service completed 2 months ago at 105000km. The battery voltage readings you mention of 10.5V-12V match what I am seeing. My multimeter shows similar inconsistent values, especially during cold starts. The battery terminal connections are clean and tight, yet the voltage keeps dropping. After your experience, I checked if my battery is original, and yes, it is the factory-fitted unit from 2014. This definitely points toward battery health being the likely culprit rather than an alternator issue. I will get a proper load test done before replacing any parts. The workshop quoted 320€ for a new battery including installation and system check. That seems in line with what you paid for the complete repair. Thanks for confirming these symptoms are common in our generation of VAG diesels. This helps narrow down the diagnosis significantly.

Having gone through the same issues and repair process, I can confirm that your troubleshooting approach is spot on. The factory-fitted battery reaching its end of life after 9 years is absolutely typical for these VAG diesels. The voltage readings from your battery terminal checks mirror my experience exactly. When my original battery started failing, the voltage regulator couldnt maintain stable power supply, leading to those fluctuating readings between 10.5V and 12V. The 320€ quote is reasonable, thats only 30€ more than what I paid last winter. One tip from my repair: have them check the alternator belt tension during installation. A slightly loose belt can affect charging performance even with a new battery. Since your car just had a service, the workshop should have records of the electrical system health. Worth asking if they noted any battery voltage concerns during those checks. My service history showed declining battery performance over the previous 6 months before it became a noticeable issue. After my battery replacement, all electrical issues disappeared completely. The consistent power supply restored normal operation to all vehicle systems.

Thanks for the detailed insights. Just heard back from the workshop, the load test confirms the battery is indeed failing. The cells are heavily degraded after 9 years of use, which explains the voltage drops and cold start problems. Called around and found a better deal at 290€ for a high-quality replacement battery with full installation. The technician mentioned checking the alternator belt as you suggested. They will also run a complete electrical system diagnostic to ensure no voltage regulator issues are hiding behind the battery problem. Going ahead with the repair next week. Really glad I asked here first instead of jumping to conclusions about the alternator. Those inconsistent voltage readings between 10.5V and 12V were the key indicator. Having the same experience from another VAG diesel owner helped confirm my suspicions about battery age being the root cause. Will update once the new battery is installed and everything is running properly again. Hoping this resolves all the electrical problems like it did in your case.