Mercedes Sprinter Overvoltage Issue Resolved

I understand your frustration. I experienced similar issues with my Sprinter. Have you examined the condition of your alternator or voltage regulator? In my case, the root cause was alternator failure resulting in high voltage.

When your alternator failed, did it cause a constant overvoltage, or was it intermittent? I'm trying to figure out if I should replace the alternator or just the voltage regulator first. Was your battery also being drained?

The overvoltage was consistent. The battery showed signs of depletion, which made diagnosis harder. I suggest seeking advice from a qualified technician. A faulty voltage regulator may be the source, but the possibility of alternator failure can't be dismissed. A professional evaluation is indispensable.

You were right! It was the voltage regulator in the alternator causing the overvoltage and draining the battery. Replaced the whole alternator. Cost me 290€, but everything's normal. Thanks for pointing me in the right direction!