Jim

I should have provided more information, I hadn't realised you couldn't see the flap.

You have seen the plenum in the area above the drivers knees, have you removed it completely? Once it is out look at the area on the side of the tunnel where it mated with the heating boxwork, you'll see an fairly large opening. That opening has a flap that shuts off the air preventing it from flowing to the above-the-knees chamber. Once I had removed the aforementioned above the knees thing it was a pretty quick investigation which revealed the blowing-freely-in-the-breeze door. Since the door swings shut from the inside the pressure of the air kept it closed, and my feet cold.

Good luck.

Kevin

__________________
'85 300SD