Hi, I'm new to the forum and have a problem with my 83 F100 stepside, 302, 4 bbl, C6. I seem to be having the opposite problem of everyone else with a/c vent issues. I cannot get air routed to the defrost or floor. I have good vacuum and I can see/hear vacuum motors operating when I move the controls, but almost all the air still comes out of the dash vents. TIA

 

The vaccum equipment may be working, but the doors that open/close may be leaking or not moving.

 

if you look back behind the radio area I bet you will find that the "infamous blend door" is the culprit. There is plenty of help on here to tell you how to fix it, just some small hinges, etc. and you will be good as new. My 84 did the same thing and it holds true to form for these year models.....time consuming but not hard to fix...Good Luck !!