i am not getting ac thru the main vents only through the floor or defrost i found a hose black with yellow not hooked to anything it has a connectorany one know where this goes and will that solve my problem its hot here in florida and i could use the help

I do not have a vacum diagram for a 85 GT but i'll try and give you some tips.
The hose you found, does it hiss when you select max a/c? If it does this hose probably fell off the vacuum pot to move the vent selection. All you have to do is reconnect it. Look under the dash and with the engine running in a/c mode, slowly move your mode selection lever and watch what happens to all of the vacuum pots. Different ones move for different positions. Like I said it should hiss if there is vacuum at that hose for the vent pot. Frank