[Bluemerc]

So we have a cargo van with rear windows that aren't heated but the invoice list heated mirrors. I know from the manual that on the control panel there is a button that would turn those on with the rear window defrost. Since I don't have that I don't have that button as well. What turns on the heated mirrors?

 

[RobbMeeX]

Heated mirrors are activated based on ambient temperature and (either dewpoint or humidity level). My 1987 Cressida simply had a mirror heater button...