[V8] Fogging Windows

[Scott Baumann / PTS Power]

Hey gang,
    My 1990 V8Q has been sitting mostly idle since Thanksgiving, when I picked up a 2000 A8.
  I drove it a few times to keep the battery up, etc, and noticed that the windows were fogging up on me.
  It did not have this problem at all before this - except a few years back, when jumping the red switch in the lower front right of the radiator brought the A/C back into play...  My fresh air door (inside - pass. side upper footwell) stays closed - which I believe is proper - since it REALLY fogs up if I try and prop it open...
 Any thoughts on what I may be missing?

Thanks
Scott in WI
2003 Navigator
2000 A8
1990 V8Q