Viano mirror heating malfunction

I encountered a similar problem on my Audi. It turned out to be a faulty temperature control module. Does the error message provide any specific details about the electrical fault?

The error message is generic, simply stating "mirror heating defective". Where was the temperature control module located in your Audi?

On the Audi, it was situated near the mirror assembly. Considering the error and the potential cable issue you mentioned, inspecting the connections near the mirror would be a good starting point. However, for a precise diagnosis on your Mercedes, a workshop visit is recommended.

Thanks for the information. I'll inspect the connections as suggested, but it seems a workshop visit is unavoidable. At least I have a place to start.