I have a 2004 Expediton NBX. (was told NBX means Sport Edition) Well the rear HVAC control wont let me switch between the over head vents to the floor vents. Right now the vent is stuck on the over head vents. the temp controls work fine and along with the speed of the air coming out. i just cant get the button to switch from over head to floor. I searched for all I could with no help. maybe im not using the right terms. anyone got any ideas that can help?