Hi,
I had a small 'incident' a couple of days ago, where I had smoke pouring from the screen and dash vents on my '78 F250 (with a/c). I quickly turned everything off, and used a halon fire extinguisher down the vent. Whatever was causing the smoke/fire seemed to stop quite quickly (I now have a cab that smells like a bonfire, but no apparent damage).
I've searched the forum as best I can, and I assume leaves in the air vents have caught fire from the blower motor resistor coils. I've since tried the fan (very briefly), and it's working on all settings, just blowing bits of burnt leaves over the dash from the screen vents.
I don't feel confident to strip out the entire heater/ac system to clear out any remaining leaves, so I'd like to simply check the condition of the resistor coils and then wire up a bypass and run the fan on full power or off until I can find a long term solution.
I can't find any explanation of how to locate and remove the resistor coils, or how to wire up a bypass - so any help would be gratefully received.

Rob.
1978 Ford F250 Ranger XLT 460 v8 Camper Special (Auto with a/c)

 

Glad you got it quick with minimal damage. Yeah, probably trash in the duct work.
The resistor is fairly easy to get to. Its up under the dash in the duct work. I'll see if I have some pictures to post.

 

Thanks, yes, it seemed like a lucky escape - I've seen some horrific pictures of fires that got out of control. Luckily I was still on the driveway and had access to an extinguisher.

Pictures would be a great help

 

1976/79 F100/350 with factory installed integral A/C (A/C controls located in the same panel as the heater controls).

A/C blower motor resistor is shown as 19706

 

Bill beat me with the pic.
There are two plastic rivets that you have to pry out, sometimes you can pry the whole resistor out, rivets and all.
Here are some more.

 

Thanks to Bill & Mike, I quickly established that the resistor coils would be behind the glove box. It was fairly easy to remove the cardboard inner and there it was - the cause of all my woes! Fortunately the damage was limited to a small amount of melting, so for the time being I've just made it safe by disconnecting the resistor coils. At least I can still run the fan on full speed if necessary

Thanks again for the help so far.

Has anyone come up with an alternative fan controller to replace the coils?

Rob.

 

Wow! I'm just glad you caught it before any major damage was done.

 

Yeah, me too - have you seen this thread? https://www.ford-trucks.com/forums/1...uck-today.html
Scary stuff!! I don't think I'll want to reconnect those coils again

 

I've got a 79 that the prev owner parked under a pine tree. Turn the defrosters on and pine needles blow out the vents. I see a thorough cleaning in the future...
Also bought a 86 cab that did catch on fire from debris.

 

More on the dash fire.... pulled the resistor coils out today, then got a piece of hose attached to the vac to get in there to try and remove as many leaves as possible. Very pleased with the result, though appalled by the amount of leaves in there (the pile in the photo are just those that wouldn't go up the hose). Now waiting for an electronic speed controller for the fan - 'cos I'm not using those coils again!!
...and a video of the inside of the vent when I started and then when I'd nearly finished -

 

I have mine completely torn down right now for resto and have been thinking about putting some kind of screen in there to avoid that.
Could you post more info on the electronic controller? That might be a better option.

 

Sure, I'll let you know how I get on - just waiting for delivery. I ordered one of these: 12-50V 480W-2000W MAX 40A DC Motor Speed Control PWM HHO RC Controller New | eBay
...and I'm hoping to use the red/black wire as the input 12v, and route the output to the black/yellow. If it works, the only issue will be the location of the switch, as I don't think the cable is very long. We'll see