It would appear the vehicle has an electrically heated front windscreen. Used sparingly with the climate control defroster.

https://www.benzworld.org/forums/attachments/w126-s-se-sec-sel-sd/347152d1292327245-climate-control-wood-trim-7-switches-f15b1b3e.jpg

https://mbworld.org/forums/new-s-class-w222/570132-how-enable-electrically-heated-windshield.html

__________________
Paul