Mercedes S Klasse Overvoltage Issue

Sounds rough. I had something similar happen with my S Klasse a while back. Lots of weird errors popping up, and the battery kept dying. Have you checked the voltage regulator on the alternator? That can cause overcharging. The alternator is supposed to keep the voltage at a steady level, usually around 14 volts. The voltage regulator controls the output, and if it goes bad, it can let the alternator pump out too much, leading to a power surge. Also, double-check all your ground connections. A bad ground can cause all sorts of electrical issues.

Thanks for the insight. Does the voltage regulator typically fail gradually, or abruptly? Could a faulty voltage regulator cause the battery to discharge even when the vehicle is not in operation?

Good question. In my experience, it can be either gradual or sudden. Sometimes you'll see flickering lights or other minor electrical gremlins before it completely fails. Other times, it just goes boom. And yes, a faulty voltage regulator can drain the battery even when the car is off. If it's stuck in a charging state, it'll keep sending power to the battery, even when it doesn't need it. Honestly, with those symptoms, I'd get it checked by a professional before you do any more damage. An electrical issue like that can be tricky and potentially damage the car ECU.

I appreciate your guidance. Based on your recommendation, I took the vehicle to a certified workshop. The diagnosis confirmed a defective battery. Replacement and associated labor amounted to 290€. The overvoltage and related electrical issues have been resolved.