Defroster Weirdness

[Mighty.Mighty_XJ]

My defroster doesn't blow on my windshield. My blend door seems to work fine as I can switch from feet to face & it even sounds like it switches to the upper vents. It does blow out the defroster vents for the side windows, but not the windshield. The sound is like there is a blockage, louder blowing as if there's something in the way of air flow.

I've never taken apart the dash in a post 96 XJ. Any ideas? Tips?