[davepl]

Uh oh. The shop is saying my heater controls are bad, so I need to sort out what they're actually supposed to do.

In the diagrams posted above, you can see there's a 2-port control head where the water valve is CLOSED with vacuum applied.

The next one shows that there's a 3-port control head, which is what the reproduction I'm using has, and that the matching water valve is OPEN with vacuum applied.

I never noticed this difference until today. Since I would have ordered a 1970, and the Classic Industries catalog for 1969 shows a different unit, I expect I have the 1970 unit. It's the one pictured at the top of the thread.

Does anyone know, or have the time to check, where vacuum is present on the 2 ports of the 3-port control when its in the various settings (heat, ac freshair, ac recirc)? Then I could check to make sure it's working.

Does anyone also know if the pictured one is a "open with vacuum" or "closed with vacuum" design?