I have owned an 1985 GT for about ten years and like to work on it and learn as things break and need to be fixed.  However my knowledge of the air condioning system needs help.  When I turn on the AC, it blows cold air, but the only place it blows from is out of the windshield defrost vents.  Like I said, I have only general knowledge of how the AC system works and any help in a specific direction would be appreciated.  Thanks, Matt  

Can't be real specific, but the AC/heater system uses vacuum hoses, vacuum motors and cables to move doors that direct and blend the air.  You'll be better off with a service manual that shows hose routing and system details.  That's if it's factory.  Your problem may be as simple as a cracked vacuum hose or some plastic part.  You could also just try taking a hard look at the selector switch, then tracing back hoses or cables from the various positions to the AC unit.  

If it's one of those dealer add-on things like was in our 84, good luck with that.  I had to tear the dashboard off the car to get at any of the parts.  

Yeah, I guess I planned on having to take off the dash to even take a look at how it works.  I can already tell that its quite a process to chase this one down.  Thanks for the info.