A heating and air conditioning system for a motor vehicle including a housing having an air outlet, a heating heat exchanger disposed inside the housing with a warm air path to heat air flowing therethrough, a warm air duct having a warm air intake opening and a warm air duct discharge opening disposed downstream of the heating heat exchanger channeling a partial flow of warm air from the warm air path to the air outlet, and a mode control damper rotatable about a rotational axis and connected downstream of the warm air duct in terms of flow, wherein the air outlet may be selectively opened completely or partially, and in a closed state may be partially or completely closed. The mode control damper functions simultaneously as the control damper for controlling the volume of air exiting the warm air duct discharge opening.