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I looked for about 30 minutes trying to find directions for adjustment, but nothing is provided. Here is what I can tell you. The air flow direction dial in the panel is attached to a cable. This cable is what changes a flap's directions and allows air to flow to different locations. Based on your description, I suspect the cable is loose and is no longer moving the flap fully to the position it needs to get the air flow into the vehicle.
Carefully remove the trim panel on the bottom right so you can gain access to where the cables connect to the heater control box. Check to see if one is loose. There should be two, one for temperature and the other for air flow direction. Place the mode dial all the way to defrost and check the cable and then do the same when you have it directed below the dash.
Let me know what you find or if you have other questions.
Monday, October 7th, 2019 AT 8:30 PM