This is a late response, which is not unusual for me, but I wanted to add some comments for anyone searching this subject in the future:
1. If you look through the peek hole behind the glovebox and operate the temperature control and the white control arm does not move, moves part way, or has erratic motion, the gear in your airmix actuator is cracked and the actuator needs replacement.
2. If you can stick a screwdriver in the hole and move the arm without using all your Herculean "strenth", the gear in your airmix actuator is cracked and the actuator needs replacement.
3. There are no user servicable parts inside the airmix actuator (i.e. you can't replace the gear) so there is no reason to take the old actuator apart other than just to see what'* in there. IIRC, the white arm is just pressed into the hollow shaft of the actuator, you just tap it out with a punch.
For reference, here'* a link that will help you change your airmix actuator: