Blower Motor Speed Control
WARNING: This page is about a different car, the 2013 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.
The HVAC module sends a PWM signal to the blower motor speed control to control the blower speed. The blower speed control provides variable ground feed for the blower motor to control the speed. A delay function provides a gradual increase or decrease in blower motor speed under all conditions.