Heated mirror, or what?

[Dr Shuffles]

I just replaced the mirror glass on the passenger side with a newer piece from the junkyard. Here's what confused me, though: the old glass had two wires plugged into the back. The only thing I can think of is heated mirror, but I had no idea that I had heated mirrors, since I don't see a switch for that. So here are the possibilities that I can see:

1. A previous owner needed to replace the whole mirror, and he just happened to find a heated one.
2. The factory installed a heated mirror by mistake.
3. I actually do have heated mirrors, I'm just too stupid to find the switch.
4. There is no switch for the heated mirrors, they're turned on automatically when something or other happens.
5. The wires aren't for heat, but for something else.

Anybody?

[1996 328ti]

We all have heated mirrors.
There is no switch.
I think they are actually always on.

[pdxmotorhead]

They come on based on outside air temp. if your OAT sensor gets damaged they stay on all the time at least that's how my 95 worked before the heaters quit.