Air Door: Description and Operation

When the air outlet is at VENT and air mix door is in full cold position, Bi-level door is fully opened. Accordingly cooling performance is improved and airflow noise from heater unit is reduced. Additionally, Bi-level door is fully closed when air mix door is in any position other than full cold position.
In B/L or B/L2 mode, auto amplifier automatically computes target vent air temperature in relation to set temperature, ambient temperature, compartment temperature and sunload. It then determines whether relationship between inlet temperature, air-mix door position and current bi-level door position on one hand and target vent air temperature on the other hand, is adequate, thus opening, closing or stopping bi-level door as required. A constant level of warm air will then be discharged to foot level and cold air to head level.




When the amount of sunload suddenly changes, the extra heat caused by sunload is counteracted by adjusting the air outlet temperature, but leaving the temperature around foot area as it is.
In FOOT mode, bi-level door is controlled according to blower operation. When blower is operating, auto amplifier automatically computes target DEF vent air temperature in relation to set temperature, ambient temperature, compartment temperature and sunload. It then determines whether relationship between inlet air temperature, air-mix door position and current bi-level door position on one hand, and target DEF vent air temperature on the other hand is adequate, thus opening, closing or stopping bi-level door as required. A moderate level (not too warm) of air temperature will then be discharged to head level. Bi-level door is held in fully closed position when air vents are set in F/D or DEF mode.