Abstract: An air-handling system for a heating, ventilation, and air conditioning system comprises a main housing, one or more selectively positionable doors, and a control mechanism. At least one of the doors is disposed in a mixing and conditioning section of the main housing to control a temperature of a flow of air to a delivery section of the main housing. Additionally, at least one of the doors is disposed in the delivery section of the main housing to control a flow of conditioned air through a plurality of conduits. The control mechanism includes one or more cam gears configured to selectively control each of the doors to provide temperature control for various modes of operation of the air-handling system. One of the cam gears includes a cam track having one or more radially inward and/or radially outward segments to mitigate mechanical hysteresis of the doors.