The cables run from the heater control to the blend door. Mine is kind of tight when I get to the hot side of center, but I couldn't see anything wrong with the cables when I had the dash apart.
The knob turns a gear which pushes/pulls on two cables that run to the blend door. If you pull the heater control screws out and pull it forward, you can see the back where the gear is. If you open the glove box, push in the tabs on the side, get the box to come out farther, then pull on the whole box, and it will come off its hinges. The cable should mount in the top right area behind the glove box,