C4 Headlight Range Control Issue

I had a similar problem with my C4 not too long ago. The symptoms sound almost identical: error in the system, light on the dash, and the beams doing their own thing. It felt like driving a wonky-eyed robot! Did you happen to check the servomotors in the headlight unit itself? They're responsible for the auto-leveling, and if one goes bad, it throws everything off. I'm not saying this is a definite thing, but it might be worth looking into.

That's interesting! I hadn't considered the servomotors directly. Where exactly are they located, and is it something I could potentially inspect myself, or am I better off leaving it to the professionals? I'm reasonably handy, but I don't want to make things worse!

The servomotors are built into the headlight assembly itself. Honestly, unless you're comfortable disassembling the headlight unit, I'd advise against messing with them. It's a delicate system, kind of like the tiny gears in a watch – easy to break something. Given the symptoms and my own experience, I'd strongly suggest taking it to a reputable workshop. They can properly diagnose it and replace the faulty servomotor. I ignored it for too long and nearly caused an accident.

Thank you so much for the advice! I suspected it might be something beyond my capabilities. I took it to a trusted workshop, and indeed, it was a defective servomotor in the headlight. The total repair cost was 1040€, but at least the issue is resolved. Your insight was invaluable!