Side mirror heating when NOT COLD???

[robnitro]

I've read a few threads but nothing conclusive on this. Tried the suggestions but it's all mythology, cause BMW is like that with some things....

How do I get the side mirror heating to work when it's NOT cold outside?
This morning was a foggy sticky time, with the mirrors fogging up.

I tried rear defroster button, of course nothing.
I put the fan on defrost mode, nothing.

Book just says mirrors come on when it's cold. Yeah BMW, how about when it's humid and foggy?

No, in a "luxury" "advanced" car I have to wipe the mirrors during my commute because their idea of automatic is stupid.