As ever with Audi's, sometimes it's not as simple as that!
I noticed m 2001 Sport defrosted the drivers door glass, but not the passenger. I popped out the passenger glass, found it was non heated, but saw the wires there all ready to connect up.
I toddled off to GSF, purchased a heated element, connected it all up and looked forward to a demisted passenger side too. Except, it didn't!
I popped the mirror off again and measured for voltage with the heated screen on and off, and detected a difference. The voltage was minuscule though, so I checked my drivers side which was exactly the same, but that demists.
I hooked up VCDS and found the measuring blocks that say whether the mirrors are currently heating or not, and found the drivers one said ON and then cycled between ON and OFF once up to temp, but the passenger one stayed OFF.
There appears to be no way of activating the passenger mirror, so for now it still doesn't work. It could be that the GSF supplied mirror part is not compatible or that it's faulty I suppose. All my testing was done in sub zero temps a few weeks back. I wonder if I should try an Audi mirror?