I spoke to Steve earlier today and he said that the ECC display is not blinking. This leads me to believe that it'* not the air mix actuator. Every other actuator failure I've seen has been accompanied by a blinking display. Nevertheless, we want to view the actuator movement to make sure that it is working properly.
Remove the inner glovebox (black fuzzy part) be removing the six 7mm screws. Lift the flap on the bottom in order to pull out from the dash. You can inspect the movent of the actuator using a flashlight and looking through the left hole in the black steel section (left of the barcode sticker about 4" as pictured above)
Here you see the air mix door lever and rod. This is in the full cold position and basically points to the driver'* B pillar. When the ECC is adjusted to full hot, the rod and lever should move smothly aproximately 90* and point to the passenger'* B pillar. Adjust to full cold and hot a couple of times to make sure there is smooth and full movement