vacuum actuated heater shutoff help

[Custom 68]

well ok I hope that title makes sense. Anyway I have got my AC running but have seen a valve that shuts off the hot water to the heater core that uses vacuum to operate.
does anybody have a part number I know they had them on several vehicles?
And how does it work is it just kindof on or off working off the AC switch or does it regulate based off the hot to cold lever? I have my inside to outside vaccum doors working but never had one of these on my original AC truck.
Any help or thoughts if I need one or not would be great.

Thanks
Dave

[clay68c10]

Any of the vendors should have these available. Just tee in the vacuum line for your recirculating air flap on the cowl. I mounted my valve to the inner fender, close the hood hinge about 6-8 inches away from the heater core inlets.
It does help with the cooling when it's really hot outside since the heater core is on the passenger side of the firewall, not out under the hood.

[neonlarry]

I like the newer versions better. Like one from a 90's van.

[Custom 68]

I was wondering if there were different ones. What is different and is this something I can get at the local auto parts store? The air is cold but figured this is supposed to be there.
Dave

[neonlarry]

The newer valves have both heater lines going through them and when activated loop the coolant back to the engine through the other line. Instead of just trying to block one line, where any leakage in the valve lets hot water flow through the heater.
I'm sure local parts has them, I just don't remember exact year van I got it from (and can't take a pic right now because the kids took the digital on a trip and won't be back for a couple weeks).

[Custom 68]

great, that does sound better than blocking one line. I will do some digging should be able to find one. If anybody has a pn or other info that would be appreciated.
I guess it is either open or closed?

[neonlarry]

Yes, either open or closed. Its to keep hot coolant out of the heater core when the A\C is on.

[red71cheyenne]

Another thing you can do is make sure the flap that closes off the heater core when you are on the cold side is fully closing. I had my R-12 checked at Ricks there in Spfld, and he said my door wasn't fully closing, keeping the hot air coming in. I tore the evap box apart and cleaned all that out and it works much better now. You'd be surprised how much crap collects in there after 30 years.