I started having issues with my Toyota A/C blend door actuator making clicking sounds and not working in certain A/C modes. I found on the forums that there are 2 common failure points, 1 of which I was experiencing.
This actuator came off my 2007 4Runner, but is apparently used across various Toyota models like the Camry, Corolla, Sienna and Tacoma.
2 Common Failure points that I found:
1. The electric contacts over time start to lose their springiness, causing the connection from the contact to the back of the gear (black part) to not make a good connection, causing the module to lose track of what position the motor is in. Additionally, the grease hardens over time causing the contacts to not contact with the gear
2. Worm gear over time apparently gets brittle or doesn't have lubrication to spin freely. When the gear gets brittle, the gear breaks off the motor shaft and spins freely or (if you're lucky) just pops off the motor shaft. When there isn't enough lubrication, the whole system binds.