Yes.
Opens and allows hot water into the heater core inside the car when you select heat.
Should close and stop hot water flow when AC is selected.
Actuated by vacume.
(Mode doors also move under dashboard to allow hot air from the core or cold air from the ac evaporator to circulate in the car).
Exacto, and I could never figure why they were not used on ALL cars. The heater core radiates quite a bit of heat on non AC cars even though there is no/ little airflow