C5 Rear Window Defroster Issue

Interesting issue. I had a similar problem with my old Audi A4 Avant – rear window defroster suddenly stopped working, and it threw a related error code. Have you checked the fuses? It might be a simple fix.

Fuses were the first thing I checked, sadly. All seem fine. Was it definitely the battery in your Audi? Or something else entirely? What did the workshop say?

In my instance, after checking fuses, the issue traced back to a failing battery. While it still started the car, its performance was degraded, affecting auxiliary systems. Given your symptoms and error message, I would suggest a professional diagnostic check. If the battery is confirmed as the problem, replacing it should resolve it, as it did for me.

Appreciate the insight! Took it to a workshop and you were right. Battery was failing. New battery fitted for 290€, and the rear window defroster is working like new. Thanks again for pointing me in the right direction!