In my experience, there is an actuator that mounts on the blower motor housing that had became stuck, or otherwise failing to switch the curved blower stator that directed the flow of air from the blower motor. Mine had failed bc of moisture from a leaking windshield/air cowl seal and had ultimately damaged the blower motor and actuator. I'm sorry if my description is lacking, but it's basically just a small rc car motor that engages when u select different fan outputs on the dash air controls. Hope it helps!