So SyncroHead@aol.com says:
> 
> >stop it!  Any ideas?  It's going to be cold soon in Colorado...
> 
> This is not normal & could be caused by a broken or improperly adjusted air
> damper.  Just to make sure you're operating it properly, here's what the
> levers do:

Here's what I found on mine.  I was having the same problem and couldn't
keep hot air from coming in.  A real bitch on hot days when you really
need the AC to reach you from the back and hot air is blowin' on you
from the front!  I tracked down the control from the top lever that
Jim mentioned by removing the lever cover, the ashtray, and then the
glove box.  Removed the glove box and looked up to the left with a
flashlight.  You can see where the wire connects to the actuator arm
which controls the flap.  Move the lever to make it easier to distinguish.
The problem in 'The Beast' was that the actuator was actually coming
off the rod that holds the flap.  This was because the little pinch
holder on the actuator would not expand enough to hold it in.  So I
stuck a little piece of cardboard in between the pinch holder and the
actuator body.  This fixed it and I only change the cardboard about
once every couple of years.  

If the actuator isn't the problem and it's not the cable adjustment,
then you have my sympathies.....

Steven 
Sacramento, CA
sjohnson@pcocd2.intel.com