The A/C in my 2003 F-150 Harley Davidson only blows cold air through the defrost vents?

The setting switches work fine but blow warm air. When I switch to "max ac" or "panel" mode, it immediately routes to the defroster. First the "max ac" went out, so i used the "panel" mode. "Panel" mode started going out slowly when i would go over 30mph...now, neither work. Could it be the PCV? Or is it a vacuum hose as others have suggested? How do I fix it and where are the locations of the affected parts? Or...should i just take it in? If i take it in, how much should it cost? Any help would be great...it was a little over 105 degress here in vegas today and no a/c is killing me!!