HVAC Air Distribution and Flaps
HVAC air distribution is the part of the climate system that moves air through the vehicle and sends it to selected cabin locations. The blower, ducts, internal doors or flaps, and visible outlets have related but different jobs.
The airflow path
- The blower creates airflow through the HVAC unit.
- Ducts carry that air toward the windscreen, dashboard, footwell, rear cabin, or other destinations.
- Blend doors or temperature flaps change how air passes through or around heating and cooling sections so the system can adjust delivered-air temperature.
- Mode doors or distribution flaps select the destination path, such as windscreen, face-level, or foot-level outlets.
- An outlet or vent is the final cabin opening. Its louvres may aim, spread, or restrict the emerging air.
Names are not perfectly standardized. An owner’s manual may call several internal components “flaps”, while a supplier may use “doors”, “mixing actuators”, or “distribution actuators”. The useful distinction is the function: mixing temperature paths is different from choosing a delivery location, and both are different from aiming the air after it reaches the visible vent.
How flaps are moved
Internal flaps can be linked directly to a control, moved through a cable or linkage, or positioned by an electric actuator. Valeo describes cable-operated flaps in manual air-conditioning systems and motor-driven mixing actuators in automatic systems; this illustrates two implementations rather than a rule for every vehicle. Valeo Service: car air-conditioning actuators
Automatic climate control can coordinate blower speed, temperature mixing, and distribution without exposing each movement to the occupant. A manual selection on a screen can also command an actuator. The type of user interface therefore does not, by itself, identify the mechanical layout behind the dashboard.
For the wider relationship between cabin heating, cooling, humidity control, and airflow, see Climate systems in electric vehicles.