Air door part question

[hdff]

Originally Posted by BrianG

Can someone explain where this is located? Is it an ac only thing maybe? I have a non ac truck and the only fresh air flap doors that I know of are in the heater box then there are one on each side that open and close with the pull/push rod in the kick panel. If there is some other door/flap I want to be sure to check it out before finishing up the restore. Also how does it open and close?

I think these are only on ac cab trucks the door is under the cowl and the vacuum actuator is on the fire wall near the blower fan. You can see the vacuum actuator in this pic