While driving my car today with the heat and defroster on, I smelt what seemed to be something burning and I saw a few whisps of smoke coming from under the dash. There is now a bad smell in the car - really hard to describe, somewhat like burning acrylic, maybe? I’m not driving it for the mean time, but would like some thoughts before I take it into the shop. It’s a 2002 Chevy Cavalier with about 130K. Any ideas?
Well does it seem like you might have a wire burning? You need a shop to look at the car but you may not want to. A burning wire could mean real money to trace and fix. You want a shop you can trust to say no it is not worth fixing. So does the defroster work? Anything seem to be not working?
I’m honestly not sure if it smells like a wire may be burning. After doing some quick research online I thought that could possibly be it, but I’m not entirely sure what that would smell like. Everything seems to be working fine, I haven’t noticed any problems with the defroster. Is there anything else that could cause a bad smell and smoke from the dash, or am I most likely looking at something electrical?
Burning wire (actually, the insulating coating on the metal wire) smells like burnt plastic – or, as you describe it, burning acrylic.
Hard to think of anything NOT electrical under the dash that would initiate a burn. However, even if something else did fire up, it could well burn nearby wires or other plastic.
Myself, I’d want to find out what’s wrong before anything worse happened. Selective sniffing around is probably the best way to locate the damage, but I imagine that getting under the dash will be difficult.
(I just got the idea of a long tube that comes into a fitting on your nose to increae your olfactory acuity – like a stethascope does for your ears.)
(someone else thought of that too 
)
Sounds like something electrical overheated, but not enough to cause a failure. Probably the wiring for your heater fan or rear defroster. Look under the dash in the general area you saw the smoke for wiring with melted or discolored insulation.
I agree. It sounds like one or more heater control resistors burning out. If so it is not un common, but exactly where they are and how to get to them varies a lot from car to car. The last one I replaces was a 1965 Sunbeam Imp so I doubt if it is going to be in the same place on your car.