A mechanism for opening and closing a damper valve of a diffuser mechanism is provided. Embodiments of the invention include a damper construction that selectively alters the amount of air flow through a diffuser grille using a three-plate damper valve. The three-plate damper valve includes a manual plate, a fixed plate, and a motorized plate. The manual plate is manually rotatable around a central axis, while the motorized plate is mechanically rotatable about the same axis. The motorized plate is mechanically and/or remotely controlled using a stepper motor coupled to the motorized plate. Further, the diffuser mechanism includes a sensor for determining the location of the motorized plate with respect to a starting position. As such, multiple configurations of the manual plate and the motorized plate may be used to alter the air flow through the resulting channels of the damper mechanism.