My wife thinks I'm a nutter now!
10pm - ambient temp in my underground carpark = 39.5c
Wing mirrors already pretty warm, and can't tell if the heating element is having any effect, or not working as it's too warm.
I doubt the heating element would raise the temperature up to 40c anyway - seems like a bit of overkill to me to clear a thin layer of ice....
LOL.
I just wondered if they worked during the heat of the day, though. In Blighty today, you needed the mirror heating to clear all the spray. And they
should get fairly hot - hot enough to draw your hand away after a few seconds. Don't forget they also need to cope with "wind chill" - if the ambient is say minus 2 C, and you are doing 60 mph, then there is a considerable chill for them to deal with.
IIRC, my RS4 mirrors heated up even during 40c (I think) when I was in Italy last year. I have heard a romour that the mirrors wont heat if the ambient is above a certain temp, but that was on old skool models, where the mirror heating was on permanently with the ignition. Even my old 1990 Cavalier heated mirrors worked great!

Thanks, anyway. Much obliged.
