Hi: I have a heater I removed from a 39 truck. It is not by Ford .Brand name is Hot Wave. It has no provision for defroster, just blows hot air into the cab.
I have not figured out how to do pictures on this site, E mail sdarr@mts.net then I can send some pics.
This heater has only one wire I assume just on or off. I have some later heaters with reversing motors and seperate fans for heat or defrost, they are larger and a little more efficient.
Stewart