marco_feuer10
B Klasse rear window heating issue
Summary of the thread
A 2020 Mercedes B Klasse experienced a failure in the rear window heating system, accompanied by an error code and reduced windshield heating performance. The issue was suspected to be linked to a discharged battery, which can cause various electrical problems. After replacing the battery and clearing the error code, the rear defroster functioned correctly again.
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4 comment(s)
marco_feuer10 (community.author)
I haven't noticed anything else obvious, but where should I even start with the battery? Is it something I can test myself, or am I better off taking it to a workshop?
peterfire54
You can check the voltage with a multimeter, but honestly, if you're not comfortable doing that, I'd suggest taking it to a workshop. In my case, the battery was heavily discharged and needed replacing. The heating coil in the rear window needs a lot of juice. The error memory will probably need to be cleared too.
marco_feuer10 (community.author)
I appreciate the advice. I took it to a workshop, and you were spot on. The battery was toast! New battery and error code cleared; the rear defroster is working perfectly now. Cost me 290€, all in. Cheers!
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MERCEDES
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BKLASSE
peterfire54
I had a similar issue on my B Klasse. The rear window demister stopped working. Check the battery first. A weak battery can cause all sorts of electrical gremlins in these cars. Have you noticed any other electrical issues?