Sorry for being late to this thread, but I finally got around to fixing my rear A/C which has been out for months. Btw - great input and photos from all contributors. It made fixing my A/C pretty easy.
Since I was having the same problem, I opted to skip the $75 dealer part cost. Instead, I found a similar actuator (in a Lincoln Mountaineer) at the junk yard and used it for parts. All the gears inside my old actuator had teeth missing. So I replaced the gear with the new ones. Here's the kicker...I noticed that no matter which position I have the selector on (ceiling or floor vents), the motor in the actuator is always turning. So there is constant pressure exerted against the gears. This seems odd. But when I re-assembled the actuator and put it all together, everything works great. However, I'm thinking it's only a matter of time until that continuous pressure on the gear teeth is going to cause one/some to break off. Considering how many people have had this problem, maybe it's a design flaw...where the motor never actually cuts-out, and this is causing the problems. Or does my system have another problem somewhere else? NOTE: The only way (I know) to tell if your actuator is doing the same thing as mine is to take it apart and plug it in with the top off. This allows the motor and gears to "pop" (not click or grind) letting you know if the motor is constantly engaged.