On the pass. inner fender theres a ac heater hose valve connected to vacuum. They made a few different versions according to AIM but it looks like only one version is repo'd. I have a non repo original that I cleaned up. My question is, what is the purpose of this valve that goes between the heater hose. Its usually rivited on. Mine has holes on the flapper part that moves back and forth to close off the flow when you put the a/c on ( I think). I dont know if its missing a rubber part inside or if its ok. It works as far as the vac goes but I dont know if its supposed to completely close off the coolant flow or what so I dont know If I should buy a new one ( repo) Mine would not completely close off the flow due to the original holes in the round flapper. There was a lot of crud in there so I dont know if the garbage in there used to be a rubber part or not.

ALL heater control valves are designed to fail in the “defroster still works” mode. Which means for your ac to work, the heater contol valve has to shut off the flow of hot water.

Not sure about the guts of them, but the valve is too shut off flow of hot water to the heating system so it can cool properly. When you activate the dash switch to a/c , the vacuum is sent to that valve to shut off water flow, hence the system cools better now. :)