Abstract: A lost motion drive assembly has a base mounting upper and lower levers which connect to the louvers of an air plenum, such as in an automobile's ventilation system. A user turns a knob between a plurality of selections, causing a gear-operated actuator to rotate. A clutch mechanism operable between the actuator and levers engages the lower lever to drive it one way in response to rotation of the knob. Upon continued rotation of the knob, a drive lug on the actuator engages the upper lever to drive it the same way while the clutch disengages from the actuator and holds the lower lever fixed. Reverse motion is obtained when the clutch engages the actuator and upper lever, after which it releases the actuator and a second drive lug engages the lower lever to return it to its starting position.