Well ya got that right Woody, This is the first winter that I've had the truck and all this time I thought that the purple knob just worked a valve. I can see now, partially, that it some how affects a diaphragm in the valve won't have it figured out till I get it removed in a few weeks.
Two reasons I was so confused is I didn't know that they had thermostatically controlled heat in the early 50's and the other is that the capillary tube is broken off or removed from mine. Now that I'm digging into it I can see a hole where the tubes clamp was screwed into the bulge in the dash pad. My 1950 Accessories Installation Manual shows the same thing on page 7, fig.2
Yes, I would agree, another timely thread!
It sounds like some of ya’ll have your heaters in a basket, here are a couple of pics of a 1950, 3604 factory installed Deluxe heater (minus the capillary tube);
http://rides.webshots.com/photo/2930706240098611668hUbRZA Denny Graham
Sandwich, IL
