Heater Setting Step 2 - Once the engine has run long enough to warm up, the heated coolant is transferred into the heater core which is located inside the passenger compartment.
Heater Hoses Step 3 - The heater and air conditioner evaporator core are housed in the same unit called a heater box or plenum. This unit is where several air deflection doors and ducts are located which divert air to various vents.
Air Deflection Door (plenum removed) Step 5 - These air control doors are actuated by cable, vacuum or electrical servo motors which can be controlled using a manual lever, or automatically from a computer.
Vacuum Control Lines