74 Duster heater valve vacuum or mechanical??

TylerW said

I'm pretty sure the original-style valve is extremely "no longer available", but you can use a generic valve in place of it. The only thing to remember is whether the valve is closed or open with vacuum applied. I don't recall which style it is supposed to have.

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I'm going through the same issue with a valve for my 69 Barracuda which has a 70 Dart A/C system in it. The original valve is essentially " unobtainium" unless you find one on EBay at some ridiculous price. The valve needs to be closed with vacuum applied and a Four Seasons 74612 from a 80's Dodge truck application looks like it will work. $7 and change from Rockauto in the 5/8" hose side.