[jdmccright]

You should be able to see the motor and the connecting actuator arms that direct the mode door and fresh/recirc door. Watch them carefully as you turn the mode knob. Do they not move at all? Do they move a little then stop? Is the movement you see a constant speed or does it slow down to a stop?

An uneven movement usually means something is sticking. It could be old grease, ingested dirt, pet hair (yes, I've seen it!), etc. I've even had the case on my own truck where the old rubber flap seals were so old they actually became sticky.

Normal movement that stops abruptly (or you can only see the motor/arms try to move) means there is something broken inside the motor. I've had the experience where a gear inside the fresh/recirc motor had a partially broken tooth that caused it to stop immediately when it rotated against the adjoining gear. In this case, since the door only rotated through 90°, I simply flipped the gear 180° so that the bad spot was never used (wish I had gotten a picture if this unique problem!)

Finally, no movement at all usually means a loss of power, bad ground, or an internal electrical break in the motor winding. A repair manual should be consulted to test the motor connectors and the wiring to it.

Hoipe this helps!