This same thing happened to me and I traced everything on that circuit.
Here is what I found out. The fuse ends had a little bit of corrosion on them, I pulled the fuse and buffed the fuse ends and fuse clips with some emery cloth. I reinstalled the fuse and it worked. Here is a list of the items on that circuit. Check and see if any of these other items works. If they do them most likely it is the rheostat (common).
Right front and rear, parking lamps.
Heater illumination lamps.
Instrument cluster illumination.

Good Luck!
Robert