The Stovebolt Site Forums The Shop Area Engine Shop Could a heater shut off valve overheat head?

I could be wrong on this - but wouldn't be the first time.
I believe the heater shut off valve was used with heaters that did not have a heater control valve. The temperature was controlled by opening or closing the outlet door.
My 55 Grumman is that way and so is the 59 Bus. I realize both are "commercial" vehicles, but both operate in this manner. The only way to change the temperature is to increase/decrease fan speed and/or open or close the door.
Consequently, in order to stop hot water flowing through your heater on a hot summer day, is to use your shut off valve.