Once upon a time (before swapping out the ACC for a manual system) I propped the flap open with a wine cork - cut a little "v" into it for the flap to have a kind of shelf to grab to; could still use the vent control to regulate the airflow. You can get in there by pulling the glove box and then peeling back the little rubber boot. Kinda tight to get your fingers in there but very do-able.