Defroster Valves and Heater Problems

[grey beard]

Defroster Duct Valve

Pilothouse truck heaters tended to be sort of minimal. The deluxe heaters had a panel under the dash to the left side of the steering column. On it were four knobs - Heaer, Air, Temp and Defrost. The air knob opened and closed a fresh air duct at the firewall and the Temp knob operated the hot water valve at the rear of the cylinder head. The heater knob was the fan switch. Some trucks had only the fan and defroster knobs. Mine had only a fan switch and a manual defrost door down on the side of the heater box that could be opened or closed by hand. The cable operated defroster valve is sort of rare, while the deluxe group is seldom seen. I found a defroster valve on one of my son’s parts trucks in Montana. I’ve only seen two of these in all my Dodge truck travels

The arm that was attached to the defroster cable and valve flap was snapped off on my valve. When I removed it from the heater box shroud I discovered why this happened. This valve fits over an opening in the shroud. When screwed into position, the shroud interfered with the flapper valve. Continual pulling and pushing on the cable to get the valve working snapped the arm off of the flapper.

I robbed a choke cable arm off of an old carburetor and attempted to mig the steel choke arm to the defroster flap valve – and immediately blew a pin hole in the shaft. Closer inspection revealed that the entire defrost valve flap and its shaft are made from white metal. These parts look exactly like steel but are not. The complete flap and shaft are made of one piece and can be removed by snapping out two small spring leaves. I will probably take this valve out and fabricate a new flap and shaft from sheet metal that can then be welded.

Lesson learned – If you find one of these defroster valves, handle it gently. Where it screws onto the main heater shroud box it must be carefully fit or the flap will interfere with the box sheet metal and something will break. The parts are tender because they are made of white metal, so handle them carefully. There aren’t a lot of these pieces around any more.

Lots of luck with your Pilohouse heater.

[Young Ed]

Dave I think I have one of those defroster valves laying on my bench at home Got a picture?