ebodell, when you say "I pulled the cowl panel" what part of the truck are you referring to? Sorry, I'm just unsure what "cowl" means. Others have used this term too and I want to be clear what that means.

 

Everything you need to get to is under the hood, just pull out the electric motor, I think there are
4 small bolts holding it in place.

Here is from a 1983+ (I think) without AC:

 

Hey Galendor,
The cowl is the panel behind the hood and in front of the windshield (the panel with the oblong holes in it). I had to pull the antenna and remove a bunch of fasteners under the hood along with the wipers and washer nozzles but I was able to get it removed so that I could vacuum it out.
I am not entirely sure that "cowl panel" is the proper term.

 

Ok, got it clear, thanks! I don't want to remove that.

 

So I pulled the fan and found a nice stash of leaves.



The photo only shows small portion of the pile that was up against the condenser and around the fan switch. It obviously was the cause of all the smoke as it had a burnt odor to it. I vacuumed out the heater box and buttoned it back up. Glad I found out about this problem.
Thanks Ctubutis!

 

Here is what happened to my '85 from leaves and straw that built up in the heater box.

 

Not hard I've done it 3-4 times now. Use a screw driver to pop the antenna plate, it should pull off the housing. Should be roughly 6-8 screw on the under hood side of the cowl near your hood seal, take those out. In the cowl itself (the vent holes) there should be about 6 screws, pull em. The tricky part is finding the right angle for the hood but once thats done the whole process is great.