The mirror uses 2 magnetic field sensors for compass direction. One sensor is for north and south, the other is for east and west. The mirror supplies a signal and low reference to each sensor. As the vehicle travels with or against the earth's magnetic pull, there will be a change in voltage on one or both sensors. As a result of the change in voltage, the mirror changes the heading on the compass display.

With the ignition ON, ignition voltage is supplied to the mirror from the IGN E fuse in the underhood fuse block. Ground for the mirror is provided by G302. The COMPASS switch is used to turn the compass on and off. With the ignition in the ON position, depress the COMPASS switch to turn the compass on. Depress the COMPASS switch again to turn the compass off. The COMPASS switch is also used to place the compass into a calibration or zone mode. For more information refer to Compass Calibration and Magnetic Variance.