When I turn my air on/off and even stop/go on the road I hear this flap shut loudly. It was never that loud before. I have not begun to take anything apart. Figured I'd ask before probing to see what it might be and if there is a possible fix?

Thanks-

 

One of the control gates is starting to fail, inside the dash, that controls air flow.

 

How complicated is it to repair? What has to be removed to get there?