Blowing out the defrost is probably a vacuum hose leak under the hood, mine was by the master cylinder. It was wrapped with some wires in a wire loom. Best of luck.........cC

 

Blower motor will run with a bad compressor. The ac system may have a low pressure switch that turns off the compressor. Seems like a good sign that it cooled with freon added. A good scenario would be to fix the leak and charge the system and not have to replace any big parts.

 

you have a freon leak.

 

Try this link. If it blows cold, then goes hot, you have a vacuum leak.

http://www.ford-trucks.com/forums/919562-heater-blowing-only-on-defrost-help-please-2.html

Try the 1997-2003 F150 section. many post there about your EXACT issue. Good luck.

 

Try this it doesn't cost anything and fixed mine twice. disconnect your battery cables and let it set overnight. resets the computer, sounds stupid but fixed mine for 4 years the first time.

 

My 2003 did that.I was a white vaccum hose coming out of the firewall by the blower motor just at the edge of the convaluted(sorry about the spelling)tubing.It got brittle and crumbled.It wouldn't hold the doors in the unit shut.I bought a piece of vaccum hose,skinned back the tubing to get to good hose,cut out the bad stuff,and slid the rubber hose over the ends.No clamps needed,and worked for another 3 or 4 years.Several guys at work had the same problem,and it was the same hose.I got to be the hero for figuring it out.

 

Could be the air gap on the compressor clutch. My old 04 f150 would blow cold then it would blow warm air as it was driven.