Smoke from vent

[Willlgord]

I’ve recently built a camper van out of a 99 Dodge 2500 high top. In the middle of a trip a couple weeks ago while driving I noticed the smell of wood burning and thought it was outside, shortly after a lot of thick smoke came out of the firewall vent below the glove box. I stopped and got my extinguisher ready and the smoke subsided. I checked both underneath the hood and chassis finding nothing. I had no problems over the rest of the trip. I kept an eye on the ammeter looking for some sort of electrical problem but it read normal, it was most definitely not an electrical smell, wood or maybe paper. What might there be in the heat/AC box that could get hot enough to ignite a fire? Neither the heat or AC was being used, is it possible some paper or cardboard was hung up on the exhaust? I think the fresh air enters at the windshield base so a fire under the van couldn’t enter there. Any ideas? Thanks!

 

[Willlgord]

I've found the source of the smoke, it turns out that when the heater motor speed control resistor burns out smoke can come out of your vents. The resistor is inside the air box and any debris that's accumulated around it catches fire....luckily a small one that goes out by itself.