1990 F-150 300/6 5spd. My A/C compressor runs, stop and start. But inside the truck it only wants to blow out the defrost (no cold air), NOT thur the dash vents. What could be the problem? I don't want to shotgun a bunch of parts at it. Is there something the most common? Thanks
Lewis

 

Check for vacuum leaks!! The most notable one is the white vacuum line that runs across the top of the A/C box under the hood...

 

thank you I'll check ll the vaccuum connctions and lines.