Sounds like you blend door actuator is hung up, or defective. The blend door diverts the airflow to the selected area. Check out this post, or search the forums for "blend door actuator"
i do agree that it could be your blend doors no working. but another good thing to check would be your controls. the controls on that model are all electronic so they have a tendency to go out. the one on my truck just went out about 3 weeks ago. the first thing that would be good to check would be that control and then if you are still getting no movement from the blend doors then check the motors on the blend doors.
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