Photo of original heater control valve install?

[davepl]

BTW, anyone care to venture a guess as to why my 1970 had a 2-port head when I got it? I thought they were all 3-port 1970 and later.

The water control valve was gone from the truck, so maybe someone swapped a 2-port in and it wasn't compatible with the 1970 water valve, so they had to remove it?

[ryanv70c10]

Originally Posted by 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?

Bump...

I have a 3 port vacuum switch on my AC controls, I purchased a new "4 Seasons" heater valve which is "closed with vacuum applied". This appears to be incorrect with the 3 port switch as I need a "open with vacuum applied" Anybody have a correct part number?

Thanks!