96 Ranger, just had a fire - diagnosis, please.

[moretsky99]

So strange. Just out of the doctors. Drove less than 1/2 mile. Smoke pouring out of the top vents in the cab. Had to jump out of the cab. So thick couldn't see. Popped the hood.
There was a fire.
Let me explain the place. The aircon hoses seem to go to small radiator just outside the firewall on the passenger side. That radiator is covered in black plastic. The fire seemed to be at the bottom, underneath this small radiator and a bit closer to the firewall. Luckily I had a bottle of water and then someone stopped with some more water.

I was still able to run the truck and was thinking to get back in and drive the 7 miles home, but the wife was there. She, and I put it mildly, objected. So had a tow back and it's now sitting in my driveway.

Ok, so what's the issue? Anyone ever have a similar problem?
Can I just disconnect the aircon and run again. I think my attempts to crack the plastic to pour water into the cavity along with the melted holes in the side of the plastic may have caused a leak in that small radiator.

Please explain and how to fix.

Thanks in advance,
A.

 

[Curious Hound]

Ok. First. The "small radiator" thst the air conditioning hoses are connected to is the evaporator coil. That is where heat is transferred from the air in the ductwork to the refrigerant inside the evaporator. That is not the source of your fire. It just happened to be close.

Between the evaporator and the heater blower motor (the black metal round thing attached to the plastic housing - the ductwork) is a small electrical connector attached to the ductwork. That connector serves a resistor bank that is used to adjust the blower motor speeds. The resistors are in there so the moving air can keep them cool. Resistors generate heat naturally. It is likely that flammable material - leaves, paper, mouse nest, etc. Accumulated in the ductwork, touching the resistors and the heat from the resistors ignited it. If this is the case, removing the blower motor fuse will prevent further fire until repairs are made.

I'm glad you were able to safely get out and extinguish the fire.

 

[RobbieD]

That is, a classic description of debris in the HVAC plenum box being ignited by the blower resistor.

 

[moretsky99]

Ok. First. The "small radiator" thst the air conditioning hoses are connected to is the evaporator coil. That is where heat is transferred from the air in the ductwork to the refrigerant inside the evaporator. That is not the source of your fire. It just happened to be close.

Between the evaporator and the heater blower motor (the black metal round thing attached to the plastic housing - the ductwork) is a small electrical connector attached to the ductwork. That connector serves a resistor bank that is used to adjust the blower motor speeds. The resistors are in there so the moving air can keep them cool. Resistors generate heat naturally. It is likely that flammable material - leaves, paper, mouse nest, etc. Accumulated in the ductwork, touching the resistors and the heat from the resistors ignited it. If this is the case, removing the blower motor fuse will prevent further fire until repairs are made.

I'm glad you were able to safely get out and extinguish the fire.

Thanks so much. I'll be sure to pull the fuse. I feel pretty stupid now. I've been hearing a whirring noise from the fan for quite a while which I completely ignored. I'll have to research that area now. I try to do my own work. My first instinct is to remove anything to do with the air conditioning. Even in the panhandle I rarely use that, but I suffer with cold. Should be an interesting fix for me and I'm glad I can run without the whole by removing the fuse. Much appreciate the info.