What's up guys. My wife's 08 Taco is driving me crazy. It started making a clicking noise around the passenger side and behind the glove box. I eliminated the filter, debris, and blower motor as the problem. I could actually visualize the air door actuator/servo causing the noise. FYI, I don't know the exact name of this part but I think it's referred to as the air door actuator or servo or air mix controller. It controls the air doors that close and open with the push of the A/C recirculation button. It appears that the servo keeps running and turning the interior gears when it should turn off. I removed the servo and opened it up to find the large white plastic gear missing a tooth. I replaced it with a Dorman replacement for $40 instead of paying over $100 for the OEM part which BTW was a PITA to find an aftermarket part since I couldn't really cross reference the toyota part and couldn't find it on any auto store websites. I replaced it and it worked fine for one day. Now I have the same problem. The servo keeps running when the doors close and the interior gears seem to keep turning which causes the clicking. I was going to open up the new Dorman part but I'm going to replace it instead. BTW, this part is found behind the glove box, above the blower motor and on the left side of the filter housing. A plastic white arm attaches to this part and opens and closes the recirc doors. I'm able to move the arm and doors without any resistance so I either got a defective part or whatever controls the actuator is malfunctioning and not turning it off. Has anyone had this problem and how did you fix it? I'm going to order an AC Delco part and see what happens. Does anyone know how the motor/servo works inside this thing as far as what tells it to turn off? Is it programmed to only turn 180* or does it turn off based on when the doors encounter resistance or does some other electronic module control it? Thanks for the help. BTW, I'll update as soon as I fix it.