really the only way you will know they are working is if the de-fog or if it's really cold you can see steam rising off of them... it's kinda cool. Otherwise you really won't know for a fact that they're working.
Yeah, they should work, but they take forever to heat up from what I could see today..!! got lots of snow last night, and I don't think that you'll see the snow melt if you stay there and STARE AT IT..!! heheh, but yes they do work...only if the rear defroster is ON.
Mine took a long time to get rid of the snow and it turned out that they put the incorrect mirror on the driver side when they built the car. The correct mirrors on my car heat up quickly and it is very noticable at -25deg.
I actually saw mine work for the first time. They were a little foggy a few days after the snow.o I turned my rear defroster on and in like 5 minutes I looked at my outside mirrors and the centers were clear and around the edges of the mirrors were still a little foggy. Yay :dunno: