[71CHEVYSHORTBED402]

Originally Posted by Andy4639

Here is a better clearer picture. The cowl vent will close only as good as the seal is and how strong the diagfram is. This stops outside air from coming into the cab. The kick panel side on the passenger side should be open.

Yes...........

Old thread but a good one. I'm working on a 1971 with a three port control valve, which I really scratched my head over #3 running to the water valve. After checking my water valve(s) today it's because it doesn't work

#3 opens vacuum when the controller is set to outside defrost (de-ice) which closes the A/C water valves I've used since? doing the opposite what it's supposed to do.

My guess is factory was using up old stock and plugged #3. Can't swear to it, I chucked the old F/W grommet, the hoses were mostly gone, though I'm 99/1 the water valve is correct.

So yeah, the above diagram for the old three port / water valves opens the valve, it's counter-intuitive, at least to me, but maybe that's why they changed them