Blend Door Actuator (Flap Motor)

Most cars have several actuators: temperature blend, air distribution (face, feet, windscreen) and fresh air or recirculation. Dual-zone and multi-zone systems have separate temperature flaps for each zone. Many actuators have a position sensor so the climate unit knows where the flap is and can calibrate its end stops.

The climate control unit drives the motor until the feedback signal reaches the target position for the requested temperature or vent.

A clicking or knocking noise behind the dashboard after switching on the ignition often points to an actuator with broken gear teeth. After replacing an actuator or disconnecting the battery, many systems need a recalibration routine, either automatic or via a scan tool.