Woody:
I saw the lever on the fan housing that diverts the air flow to floor or defrost....whats the purpose of the tall skinny flap door if not to draw cab air back in....it's drawing air on the back side of the squirrel cage. I'm Just guessing .
Jimmi

1954 Chevy 3100 5-Window
In the Stovebolt Gallery
More pix on Photobucket

"True victory is victory over one's self."
Krav Maga isn't pretty ... but it works just fine.

Jimmi V.