Principles of Operation
WARNING: This page is about a different car, the 2007 Mercury Mariner and 2007 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.
The instrument cluster sends a signal to the instrument panel dimmer switch. The instrument cluster provides a variable pulse width modulated (PWM) signal to the dimmable backlighting components in accordance with the position of the instrument panel dimmer switch.