Unless you remove the underhood plastic cowling as I did you can not see whether the flap is set to outside/fresh or recirculating air. Once you do that you will understand how it works. Again when the car is started the system defaults to recirculating for 30 minutes, that fact is in the owners manual. The simplest way to manually control it is to put a switch as I did. If you have no cabin odor then you have no need for it. If you do then this is a solution.