Circuit Description
WARNING: This page is about a different car, the 2002 Toyota Prius. However, it is still accessible from the selected car via links, so may be relevant.
The blower motor is operated by signals from the A/C amplifier.
Blower motor speed signals are transmitted by changes in the Duty Ratio.
Duty Ratio is the ratio of the period of continuity in one cycle. For example, if A is the period of continuity in one cycle, and B is the period of non-continuity.