[0311Chevy8152]

Originally Posted by SS Tim

All trucks have a direct manual operation driver's inet air vent.
On non-A/C trucks there is a matching direct manual operation passenger inlet air vent.
However on A/C trucks like yours, was, this became the air recirculation door. It is vacuum motor operated to allow interior air to be sucked into the A/C inlet plenum when the outside/fresh air door (also vacuum motor operated) is closed.

Might be best to review the factory service manual on the A/C system if the picture does not clear this up for you.


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Thank you very much. I didn't realize the a/c systems were that advanced back then. Make sense.