Air Control Door
WARNING: This page is about a different car, the 1995 Mazda B4000, 1995 Mazda B3000, and 1995 Mazda B2300. However, it is still accessible from the selected car via links, so may be relevant.
When 8 in. Hg or more is applied to vacuum motor, door should stay in appropriate position for as long as vacuum is applied. If vacuum bleeds off and door returns to rest position, replace vacuum motor.