On my 2003 explorer the blend door actuator is located buried under the dash above and to the right of the gas pedal. The console has to come out to get to it plus part of the dash. It is about the size of a pack of cigarettes held in by two or three screws with an electrical connection, color black. The arm is not doing the clicking. It's the electrical actuator. It has a gear on it. It's made of plastic. One tooth breaks and it begins to click when it tries to move the arm. When two teeth break, the clicking will stop and it will not longer change the settings. There is a workaround for a 14 year old vehicle. Drilling a small hole in the side of the dash near the glovebox and attaching a wire to the arm. Once the engine is started you can pull the wire to move the door, it will stay in place. Once the engine is turn off, the position defaults back to it's normal location. I once saw a video on the net showing how the workaround was accomplished. Check for the video.
