V90 Overvoltage Errors

Overvoltage is nasty business. That many errors and system failures definitely point to a serious electrical issue. The weak battery is a big clue. Have you checked the alternator output? An alternator running wild can cause overvoltage and fry components. Also, inspect the battery terminals and grounding points for corrosion or loose connections. Bad grounds can cause all sorts of weird electrical behavior.

Thanks for the quick reply! How exactly would I check the alternator output? I'm not super familiar with that. Also, where are the main grounding points located on the V90? I can check those for corrosion, but I'm not sure where to look.

Checking the alternator requires a multimeter. You'd measure the voltage at the battery while the engine is running. It should be around 14V. Anything significantly higher points to a faulty voltage regulator in the alternator. As for grounding points, look for thick black cables bolted to the chassis, often near the engine, battery, and inner fenders. Given the overvoltage errors, weak battery, and system failures, I strongly recommend having a qualified technician diagnose the issue. Continuing to drive it could cause further damage.

Thanks for the advice, I really appreciate it. I took it to the workshop, and it turned out the car battery was heavily discharged and defective, they replaced it for around 290€. Now the car runs great!