Smoke from under the dash

[67cruiser]

67 C10 I was having headlight problems, pulled the headlight switch traced out the wiring to my bright switch on floor panel. Believe I had a loose connection down there recrimped all 3 wires, put headlight switch back in and headlights worked. Turned the knob to check instrument panel dimmer (ccw rotation) and smoke started pouring out from under my dash. Noticed on switch when it is turned all the way CCW it pushes down a contact and grounds it not sure what that does if for dome lamp ground or what. Ran out of daylight before I could pull switch again. Any help would be great. Also have a vibration problem when I get going above 55mph. It starts shaking the cab not real bad but very annoying. Somebody told me start with the U-joints, does that sound like the problem.

[WorkinLonghorn]

Better find that short.Should be easy.Nothing worse than barreling along in traffic on the freeway and all of a sudden having smoke fill the cab.
As far as the shaking,I'd check the tire balance 1st.-cougar

[Aarons72s]

Probably bad switch. Go to oreillys and get a new one. Not to expensive. You can get a borg warner or delco. The borg warner is stocked at most of the stores. You may also want a new dimmer switch to, the one on the floor, they are cheap and also in stock. Disconnect your dome light wires from the fuse panel and test them for shorting out, it might be shorting out under your driver sill plate. I have seen the dome light cable get cut by those sill plates after years of use. Try there first. Hope this helps.