[Greg Stoddard]

Do you have the auto temp on? If so and it is trying to heat the car then the air is being redirected to the floor vents. The side vents work weither you are heating or cooling the vehicle.

 

[Greg Stoddard]

I would suspect if you can't get any air to come out of the upper center vents no matter what setting you put the airflow on then there is either a bad electical connection in the controll unit or there is a cable loose from the diverter in the airflow box. Either will require taking apart the center of the dash to see what's going on.