I have a 51 F2 with the Firestone add on heater. Did they use any type of water temperature control valve? If so how was it controlled? There is nothing in the heater hoses so the hot water is constantly flowing to the heater. Does anybody have any diagrams or pictures of the control valve set up? Thanks for your help.

 

The recirculating heaters were either flowing or not, controlled only by a manual valve on the block. I added a later Ford control valve with a cable to control it. Honestly, I use it maybe twice a year, Spring and Fall. If the fan is off, not that much heat comes out of it.