If you have the heated mirrors (you can tell by the little insignia on the mirrors itself) they turn on automatically when you turn on the heated rear window. They are on the same circuit and I believe all manufacturers make them work together that way. How can you tell if there working? Wait till you have a day when the outside mirrors frost/fog up, then turn on the heated rear window (which is probably frosted/fogged up also) and everything should clear up.
Edited by - crewzin on 04/25/2003 17:00:01