Re: 2001 seville sts
Yes, they are all heated and the drivers side is electrochromatic (auto dimming).
If it is foggy, the seal is leaking and the mirror needs to be replaced.
The heat is controlled by the rear defroster switch and is activated when rear defrost is commanded on.
They all have a backing plate with the heat grid in it.
Looks like this on the back side
P.S.
I edited your title to make it more descriptive.
Yes, they are all heated and the drivers side is electrochromatic (auto dimming).
If it is foggy, the seal is leaking and the mirror needs to be replaced.
The heat is controlled by the rear defroster switch and is activated when rear defrost is commanded on.
They all have a backing plate with the heat grid in it.
Looks like this on the back side
P.S.
I edited your title to make it more descriptive.