The Bradley GT II Electric was equipped with a defroster but not a heater. The defroster unit was positioned under the dashboard in a fiberglass plenum that was integral with the firewall and molded into the body of the car. Fresh air was drawn by a fan thru a hole in the forward face of the plenum (the car’s firewall), was warmed by a set of three resistance coils and was ducted to a pair of outlets on the top of the car’s glare shield. One relay controlled power to the blower motor and a second relay controlled power to the heating coils. Switches on the instrument panel controlled the relays.
When I received my car, several modifications had been made to the system. The air inlet hole in the firewall had been blocked off with, of all things, a round amber lens from a school bus’ turn signal. Hey — it was the right size! A smaller inlet hole was drilled into the plenum on the passenger-side of the firewall, reducing the fresh air feed from outside the car. Two trapezoidal holes were cut into the plenum cover. You can see these in the photos above. Adding these holes had the effect of recirculating cabin air thru the defroster. Presumably, the cabin air would have been warmer, making the defroster more effective. There were no valves or dampers in the system, so the relative amounts of recirculated and fresh air were determined simply by the sizes of the holes thru which the air flowed.
The outlet side of the system was also altered. One of the outlets in the plenum chamber cover was ducted to both defroster outlets with hoses and a tee fitting. The other outlet in the plenum chamber cover had a small louvre. This had the effect of directing some of the air from the defroster down towards the driver’s feet. Again, there were no dampers in the system but by closing the defroster vents, all of the air would have been directed towards the floor of the car under the instrument panel. The modifications were really quite clever and probably aided in improving the comfort of the occuppants.
The photos show how the whole thing was assembled. I’m toying with the idea of adding a few further modifications. I’d like to put dampers on the trapezoidal holes. I’d also like to re-open the original hole thru the firewall and add a damper there. Finally, the smaller hole thru the firewall — the one added by a previous builder — would be sealed off. This would have the effect of controlling the relative mix of inside and outside air — similar to what you find in most production cars. I don’t know if I can do this, but I’m going to start thinking about it.