Chrysler Repair: air vent chattering- 05 grand cherokee, jeep grand cherokee, air vent

Question
Hi Kevin, i have an 05 Jeep Grand Cherokee, the air vents have started too chatter upon start up of the vehicle. It usually starts in the passenger side under the dash, and chatters for about 20 seconds then stops most of the time, on occasion it will continue to the vent in the center of the dash. The chattering will stop until you make a change on the a/c controls (temp or fan). I am at a lost for here to start with this problem, any advice that you could give would be greatly appreciated.
Thanks Corey

Answer
I have seen this b4 but each time a different door  Thea gear is striped or broken for what ever is making the noise  Look under the dash pass side and look at the motors for each door  mode,vent,and blend see which one is making the noise  Vary possible haft to R and R dash to replace which ever is broken.