Principles of Operation

WARNING: This page is about a different car, the 2009 Mercury Sable, 2009 Ford Taurus X, and 2009 Ford Taurus. However, it is still accessible from the selected car via links, so may be relevant.

Steering Column Switches - The steering column switches include the ignition switch and the multifunction switch (high beam/low beam, flash-to-pass, turn signal and windshield wiper).

Ignition Switch - The ignition switch is controlled by the ignition lock cylinder with a key. When the ignition lock cylinder is turned using the key, a mechanical connection positions the ignition switch to the selected position and allows the ignition switch to send voltage to various components and systems. The ignition switch also contains a key-in ignition system that allows the Smart Junction Box (SJB) to detect when the key has been inserted into the ignition switch. The available ignition switch positions are:

OFF
ACC
RUN
START

Multifunction Switch - The multifunction switch controls the various components (high beam headlamps, flash-to-pass, turn signal and windshield wiper) by grounding certain SJB circuits and wiper motor circuits. When the SJB detects the specific ground, it sends a voltage to the appropriate component to activate it. The SJB controls the high beam headlamps, the flash-to-pass and the turn signals. The high beam headlamp and the turn signal portion are normally open switches that close when activated. The flash-to-pass switch is a momentary contact switch that grounds the SJB high beam headlamp circuit. The windshield wipe and wash functions are controlled directly by the multifunction switch, wiper and washer motor.

For multifunction switch concerns, refer to one of the following articles:

For exterior lighting, refer to EXTERIOR LIGHTING article.
For wipers and washers, refer to WIPERS AND WASHERS article.