Fogging Windshield

[hikelsey]

With great direction from a Forum contributor, I've diagnosed a problem. My windshield fogs considerably on the outside on humid days with the AC on. Switching from AC to Defogger produces no noticeable change in air velocity on the windshield. I'm told that the problem is a vacuum controlled air direction mechanism that is stuck open. Any advice available on fixing this problem?...........and maybe someday I'll gain enough experience to be able to offer help myself! Thanks folks!