Recirc stuck on open position

My ac/heat unit has a recirc button on it to either use air from outside of the car or recirculate the inside air. Problem is.........it only works on outside air mode. When i press the button it illuminates telling me that its not the button. Is there a door under the dash "accuator" that is stuck in which i can fix mysellf? Or maybe a vacuum leak?

Does anyone have any knowledge of this?