2004 Sienna XLE Ltd Clicking Sound in Dash

[Attempt6]

For the last couple of days, I've been getting a clicking sound intermittently from under the dash. It happens as soon as I start the van. Sounded almost like the turn signals clicking. Without tearing the dashboard apart, I was able to see that the sound was coming from a white plastic arm with attached gear in the vicinity of the driver's right leg (within the central area that houses the hvac/radio controls). The arm was moving back and forth creating the clicking sound.

If I turn off the hvac, the arm still cycles back and forth. I tried selecting the recirculate air button and I could hear the door open/close yet the arm still cycled, so it does not seem to be the recirculate door.

The hvac system seems to be working OK, but I'm concerned that whatever's failing will soon fail catastrophically, but I can't afford to pay a couple hundred bucks just to have it diagnosed.

Anybody have an idea what this could be?

[Attempt6]

In my old age I'm getting forgetful, but I believe that a local deal told me it was a servo motor on a blend door. Cost of repair estimated at about $350.