marco_feuer10

B Klasse rear window heating issue

My 2020 Mercedes B Klasse with a gasoline engine is playing up. The rear window heating is completely dead with 66206 km on the clock. The car's computer is throwing an error, and the windshield heating isn't performing as well as it used to. Could a discharged battery really cause the car defrost to fail like this?

4 comment(s)

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?

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?

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.

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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