The doors that controll where the air comes out are operated by vacumne, which means you NEED vacumne for them to operate. When you have no vacumne the default is to have the defroster vent open. so you need to check your source of vacumne and fix it
Othertonka
2004 Southwind 32VS 8.1 Workhorse chassis
2002 CRV Toad
U. S. Gear Unified brake system
Retired Fire Captain, SFD