Oh come on, we're lucky that a heater was standard equipment, aren't we?
The switch for the fan speed was the only control (air movement over the "radiator") on the standard heater. For us southerners (I'm from VA), there were aftermarket heater flow valves that could be installed at the engine side of inlet water hoses. This way, in summer you could turn off all the water flow to the heater. "Chevs of the 40s" use to sell these valves. Being cheap, I use to disconnect the hoses to the heater during the summer (took off one hose altogether and ran the other hose from heater inlet-to-outlet on the engine side).
Tim
