Volvo VHD - Manual (Page 109)

Instruments and Controls 103
Heated Mirror Switch (option)
The vehicle can be equipped with heated
mirrors. The switch turns on an electric
heater element that is a part of the mirror
glass. The heater is self regulating and will
keep a steady temperature after reaching
operating temperature. Both top and bottom
mirrors are heated.
Turning the switch on activates a telltale in
the instrument cluster. The telltale will stay
on until the switch is turned off. W3003492