Upper arm controls the heater valve. In the extreme right position of the lever, the valve is fully open and the largest amount of coolant passes through the heater radiator; on the far left - the valve is completely closed and no liquid enters the heater radiator.
Middle lever controls the air intake hatch cover. In the extreme right position of the lever, the maximum amount of air enters the passenger compartment, and in the extreme left position, no air enters.
Lower arm controls the distribution of air flows to blow air onto the windshield (extreme right position) and front door glass (extreme left position).
The source is on the website: VAZBOOK.RU