Automatic Air Flow Control

WARNING: This page is about a different car, the 2011 Nissan Leaf. However, it is still accessible from the selected car via links, so may be relevant.

A/C auto amp. decides target air flow according to target air mix door opening angle.
A/C auto amp. changes voltage to power transistor gate and controls air flow in a continuous range (no steps) so that target air flow is achieved. At this time, the voltage applied to the blower fan motor is changed at the rate of 1.0 Volt per second in order to prevent any sudden changes in air flow.
When air outlet is VENT or B/L, the minimum air flow is changed depending on sunload.

Fig 1: Blower Motor Voltage Versus Target Air Mix Door Angle Graph
Courtesy of NISSAN MOTOR CO., U.S.A.