Heater Mode Selector Not Working

[RBbonfire]

My heater won't change Modes.  Stuck on the middle vents and won't change to floor or defrost.  Anyone know what I am looking at in terms of repairs?

Thanks.

[RX400h]

This post may be relevant. Different vehicle but similar symptoms

 

[Edp1]

I have the same problem now with my sc430. All bottoms operate but the mode switch will not change the direction of airflow. It is stuck blowing on the window. Nothing changes when I send it to the floor or in my face.