2003 Ford Ranger AC problem no pressure through vents only

My ac was working fine then one day I only got air pushed from the vent through the windshield defroster vents. My friend saw a plug under the glove compartment and reconnected it and now I got air going through all the vents, but the problem has reappeared and I don't get air pressure through any of the vents except the defrost vents just below the windshield. What could it be. Thank you very much for your help I will do my best to give good points for good answer, and I will try anything you tell me. Have a great day. No make it a great day. Bless