VW Touran Battery Issues Causing Multiple Failures

I experienced similar symptoms with my 2008 VW Passat last winter. Having some experience with car electrical systems, I first suspected a simple dead battery case, but it turned out to be more complex. After checking the battery terminals and attempting battery charging at home, the problems persisted. The workshop diagnosed a faulty battery sensor, which was causing incorrect readings and affecting the whole charging system. This explained why the car kept showing various electrical issues despite having a relatively healthy battery. The repair included: Complete battery system diagnosis, Replacement of the battery sensor, System recalibration, Battery charging and testing Total cost was 315€ including parts and labor. Since the fix, all electrical systems have worked perfectly. For your Touran situation, could you share: When was the last battery replacement? Does the battery warning light stay on while driving? Have you noticed any alternator noise? Are the electrical issues constant or intermittent? This information would help determine if you're facing a similar battery sensor issue or perhaps something different in the charging system.

Last had it serviced 2 months ago, when they flagged potential electrical issues but didnt find anything concrete. After reading your detailed experience, I checked my repair records and noticed the original battery has never been replaced in my 96565km of ownership. Given the age, this could explain the cascade of electrical problems. The battery warning light flickers occasionally during driving, especially when using multiple electrical accessories. No unusual alternator sounds, but the starting power keeps getting weaker each morning. The error messages are becoming more frequent, appearing almost daily now. I think I will need both the battery replacement and system diagnosis to be safe. The battery failure symptoms match my situation exactly, but given the age of the car, a full electrical system check seems prudent. Would you recommend having the battery sensor checked as part of the diagnosis?

Thanks for the additional details about your Touran. Based on my experience with the same issues, a 17-year-old original battery is definitely due for replacement. The battery drain symptoms you describe match exactly what I encountered before my repairs. The flickering warning light and weak morning starts strongly suggest both a discharged battery and potential charging system issues. Since the vehicle battery has never been replaced, starting with a new battery is logical, but do insist on checking the battery sensor too. In my case, the faulty sensor continued causing problems even after battery replacement until it was specifically addressed. The full diagnosis should cover: Battery capacity test, Battery sensor function check, Alternator output measurement, Parasitic drain test My repair costs broke down to: New battery: 180€, Battery sensor: 85€, Diagnostic work: 50€ The complete fix restored all electrical systems to normal operation. The error messages cleared, lighting returned to full brightness, and cold starting became reliable again. Just ensure the workshop performs a proper system reset after installing the new components to avoid lingering error codes.

Thanks for the helpful input. After considering all the advice and my car's symptoms, I decided to book a full electrical diagnosis next week. You convinced me that while my discharged battery is likely the main culprit after 17 years, I should check the entire charging system, including the battery sensor. The weakening start power and increasing frequency of electrical issues match the battery failure symptoms described. I will have them perform the complete system check including the battery capacity test, sensor function, alternator output and parasitic drain test. The total estimated cost of 315€ for similar repairs on the Passat gives me a good budget reference. Will definitely insist on both the new car battery and sensor inspection given my vehicle's age. The diagnostic fees seem worth it to ensure there are no underlying problems that could affect a new battery. Really hoping this resolves all the error messages and dim lighting issues I have been experiencing. My mechanic can see me next Tuesday, so I will update once I know the actual cause and repair costs. Seems this is a fairly common issue with aging VWs, so documenting the fix could help others.