Principles of Operation

WARNING: This page is about a different car, the 2010 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.

The steering column switches include the ignition switch and the multi-function 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 the battery junction box (BJB) and the central junction box (CJB). The available ignition switch positions are:

OFF
ACC
RUN
START

Multi-Function Switch

NOTE: For multi-function switch concerns, refer to one of the following articles:

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

The multi-function switch controls the various components (high beam headlamps, flash-to-pass, turn signal and windshield wiper) by grounding certain lighting control module (LCM) circuits and wiper motor circuits. When the LCM detects the specific ground, it sends a voltage to the appropriate component to activate it. The LCM controls the high beam headlamps and the flash-to-pass. The turn signals are controlled directly by the multi-function switch. 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 LCM high beam headlamp circuit. The windshield wipe and wash functions are controlled directly by the multi-function switch, wiper and washer motor.