Peugeot Expert Rear Window Heating Problem

Hey, I had a similar issue with my old Saab 9-3. Rear window demister packed in, and it turned out to be a heavily discharged battery. Modern cars are super sensitive to voltage drops, and the body control module can throw a fit and disable non-essential functions like the window heater. It’s like the car is saying, "I'm conserving power!" because the battery is weak. Have you checked the battery's condition? Is it holding a charge properly?

That's an interesting point! I hadn't thought about the battery. How did you figure out it was the battery in your Saab? Did you have any other symptoms?

Well, besides the rear window defroster not working, the car was a bit sluggish to start, especially on cold mornings. Also, the auto start/stop stopped working. I initially thought it was something else entirely, chasing down wiring diagrams and checking relays. Eventually, a mechanic pointed out that the battery voltage was low under load. A new battery sorted everything out. Best to get it checked professionally – they can properly test the battery and the charging system. My guess is, the error code might be related to undervoltage. That's what my mechanic said anyway.

Thanks a lot for the advice! I'll get the battery checked out at a workshop. You've saved me a lot of time and frustration. It indeed turned out to be the battery. The battery was heavily discharged and defective. Replacing the battery fixed the issue, but cost me 290€. Thanks again for pointing me in the right direction!