[idmetro]

Chantz;

On my 86 the air for the heater/defroster pulls from the louvered area at the base of the windshield. When it's full of snow I can also blow some into the cab but as the truck warms up that goes away. I'd suggest clearing that area out as best as you can to lessen the problem.

I don't know if the defrost deflector in your heater case is vacuum actuated (mine is) but you might check to make sure you don't have a leak in the vacuum hose to the actuator and/or if your's is cable actuated make sure the cable housing hasn't come loose from the clamp.

In addition there is a foam gasket between the heater housing and the duct that goes to the defrost vent. Yours might have degraded or fallen out.

As for running the wire to the back of the truck; why not run it inside the frame rail until you get to the back of the truck and then bring it through the floor? You'll probably have to drill a hole to do so but you could position it under the seat out of harms way.