Serena Fog Sensor Air Conditioning Issue

I have a Serena as well, though I can't say I've reached that mileage yet. Your symptoms do sound remarkably similar to an issue I encountered last year. Did you by any chance inspect the cable and plug connection to the fog sensor itself? In my case, it turned out to be a corroded connector causing all sorts of havoc with the climate control system.

Interesting. I hadn't considered corrosion specifically. Where exactly is the fog sensor located, and is it easily accessible? I'd like to inspect the connector before I start throwing parts at the problem. Any tips on accessing it without damaging anything?

The fog sensor is typically mounted near the base of the rearview mirror, on the windshield. Accessing it usually involves carefully removing the plastic trim around the mirror assembly. However, given the complexity of the interconnected systems, I would strongly suggest having a qualified technician diagnose it properly before attempting any repairs yourself. A defective cable or plug connection is the most probable cause according to the error code, but without proper diagnostic tools, it's difficult to be certain. I ended up taking mine to the workshop.

Thanks for the advice. I checked the connector as you suggested, and it looked fine. Decided to bring it to my mechanic who identified the defective cable. The final repair cost 95€, and everything is working as expected now.