01 Windstar air issue

So I have an 01 Windstar with an air something issue.

When I select cold or warm I hear a knocking in the dash board, kind of behind the center unit area.

Does anyone know what that could be?

Also if its related or not, No matter where i select my cold/warm to blow it doesnt change. Like it always seems to blow from the window defrost ports as opposed to the dash air vents or even the floor.

For what I gather the rear stuff works ok.

Any help would be greatly appreciated
Thanks
TK