Hot air out of defrost vents when moving.

[Rust-O-Matic]

Hi guys, I need to look through my manual a little closer, but thought I would get your opinions as well. My '66 has (what I believe to be) the deluxe heater and factory AC (compressor, etc. all missing). The heater levers are all broken off, and one on the right is stuck, but the others seem to still operate their cables. The AC knobs are all there, and appear to move their cables as well.

I recently got the truck licensed and noticed after driving a few miles it gets pretty warm in the cab. This weekend I played around with it a little bit, and noticed at highway speed there is hot air blowing out of the driver side defrost vent. It doesn't matter if the lever is set to floor or defrost, it still blasts out of the defrost vent. I tried pulling the "recirculate" AC knob, which sounds like it is opening and closing a door, but it doesn't seem to make any noticeable difference.

To clarify, the blower fan doesn't appear to be working at all. It's on my list of crap to troubleshoot soon, too. The heat is only coming out of the defrost vent when the truck is moving, which makes me think something is stuck open and allowing outside air through the heater core. I'm not exactly sure where to look though. Any ideas?