Very nice work you made of your heater, Deve! Methinks that belongs more on a display wall than hidden away behind a truck's dash
Regarding some sort of ON-light for the heat:
howabout drilling a tiny hole in the mounting surface (or dash) just under the lip of the switch knob and install (glue) a mini-LED just as it pokes through the surface there? ..and connecting to the LED legs of course.
Or expand the switch mounting hole a tad and mount the LED just next to the securing nut?
Or (more complicated) install a mini-LED on the underside of the knob itself -- perhaps in its structural web -- and use a length of fine stranded wire to the PWM.
Alterative to the wire, perhaps a set of mini contact brushes??
Or a laser light clipped to the headliner and powered so it projects onto the knob when you call for heat.
Heck, even some newer lasers can clearly project words like "HEAT" or "LIGHT UP SOME WEED" anywhere you want them -- although 15 letters might take up way too much area.
Gee, so many ideas with so little time left...
