[wazzz]

Originally Posted by leadrsa729

So there’s an inner flap somewhere? Where is this located?

Thanks for the help here!

If you look closely at the pics on this page, you can see the flapper inside. It is perpendicular to the outside diaphragm shutters and moves on the shutter axle. When the diaphragm is fully open, it closes entirely the flow to the cabin. Hence the heat is diverted towards outside air through the diaphragm.