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For 1990-2009 cars only

Automatic Day-Night Mirror System Components

The automatic day-night mirror system consist of the following components:

    • Inside rearview mirror
    • Driver outside rearview mirror

Automatic Day-Night Mirror System Operation

With the ignition switch in the ON position, ignition 1 voltage is supplied through the IGN 1 fuse to the inside rearview mirror. The inside rearview mirror uses 2 photocell sensors in order to determine light conditions in the front and the back of the vehicle. At night, with automatic day-night feature enable, the mirror automatically darkens to reduce the glare from the headlamps from behind. In the daytime, the mirror is in a normal state. With the gear selector lever in the REVERSE position, backup lamp supply voltage is supplied as an input to the inside rearview mirror. The automatic day-night mirror will gradually change to a normal state as a result of the backup lamp supply voltage input. Ground for the inside rearview mirror is provided by G203.

The inside rearview mirror will also darken the driver outside rearview mirror. The inside rearview mirror supplies a low reference circuit and a signal circuit to the driver outside rearview mirror. Refer to Outside Mirror Description and Operation in Doors for further description and operation of the driver outside rearview mirror.

Temperature Display

The inside rearview mirror supplies a 5 volt signal circuit and low reference circuit to the ambient air temperature sensor. The inside rearview mirror monitors and records the voltage on the signal circuit of the ambient air temperature sensor. The inside rearview mirror uses this recorded voltage to display the temperature on the temperature display portion of the compass/temperature display. The temperature display will show "ICE" when the ignition is first turned on and the current temperature is 3°C (37°F) or below. The display will toggle between "ICE" and the actual outside temperature for approximately 4 minutes.

The mirror will display "OC" if the mirror senses a temperature of less than -40°C (-40°F).

the mirror will display a "SC" if the mirror senses a temperature of greater than 112°C (143°F).

Temperature Display Update Process

The inside rearview mirror has a temperature program that takes in account the fact that the radiator will heat the ambient air temperature sensor if the radiator is warm and the vehicle is not moving. If the vehicle has been off for more than 2 hours, the mirror temperature program assumes that the radiator has cooled and that the temperature supplied by the ambient air temperature sensor is accurate. Because of this, if the vehicle has been off for more than 2 hours, the mirror displays the temperature as reported by the ambient air temperature sensor. When the ambient air temperature sensor reports a new temperature to the mirror, one of the following cases will apply:

    • Ignition is off for more than 2 hours, then is turned on for more than 3 minutes. The outside temperature is greater than the last temperature recorded by the mirror for 2 minutes. The mirror will increase the last temperature reading by one degree every 2 minutes for 8 consecutive times. If the outside temperature is not matched after the 8th update, the mirror will then display the current outside temperature.
    • Ignition is off for more than 2 hours, then is turned on for less than 3 minutes. The mirror will update the temperature display every 2 seconds.
    • Ignition is off for more than 2 hours, then is turned on for more than 3 minutes. The outside temperature is less than the last temperature recorded by the mirror. The mirror will then display the current outside temperature.
    • Ignition has been off for less than 2 hours. The outside temperature is greater than the last temperature recorded by the mirror for 2 minutes. The mirror will increase the last temperature reading by one degree every 2 minutes for the 8 consecutive times. If the outside temperature is not matched after the 8th update, the mirror will then display the current outside temperature.
    • Ignition has been off for less than 2 hours. The outside temperature is greater than the last temperature recorded by the mirror, but the ignition is cycled from on to off within 2 minutes. The mirror will display the old temperature.
    • Ignition has been off for less than 2 hours. The outside temperature is less than the last temperature recorded by the mirror. The mirror will then display the current outside temperature.

Compass

The electronic compass includes a magnetic field sensor and a microprocessor. The microprocessor receives inputs from the sensor, processes these inputs, and provides a heading on the compass/temperature display.

Automatic Day-Night Mirror Switches (w/o OnStar®)

The automatic day-night mirror has 2 switches that perform the following functions:

    • The TEMP switch is used to enable or disable the temperature display and the automatic day-night feature of the mirror. With the ignition in the ON position, depress the TEMP switch to enable the temperature display. Depress the TEMP switch again to disable the temperature display. The TEMP switch can be held for 3 seconds in order to change the display from Fahrenheit (°F) to Celsius (°C), or from Celsius (°C) to Fahrenheit (°F). Depress the TEMP switch for 15 seconds to enable the automatic day-night feature of the mirror. A green indicator will illuminate on the mirror when the automatic day-night feature is enabled. To disable the automatic day-night feature of the mirror, depress the TEMP switch for 15 seconds.
    • The COMP switch is used to turn the compass on and off. With the ignition in the ON position, depress the COMP switch to turn the compass on. Depress the COMP switch again to turn the compass off. The COMP switch is also used to place the compass into a calibration or zone mode. For more information, refer to Compass Calibration and Magnetic Variance .

Automatic Day-Night Mirror Switch (w/ OnStar®)


Object Number: 671554  Size: SH

This is the on/off switch for the automatic day-night mirror. The on/off switch is used to perform the following functions:

    • To enable or disable the automatic day-night feature of the mirror. With the ignition in the ON position, depress and hold the on/off switch for 6 seconds to enable the automatic day-night feature of the mirror. A green indicator will illuminate on the mirror when the automatic day-night feature is enabled. To disable the automatic day-night feature of the mirror, depress and hold the on/off switch for 6 seconds.
    • To turn the compass/temperature display on and off. With the ignition in the ON position, depress the on/off switch to turn the compass/temperature display on. Depress the on/off switch again to turn the compass/temperature display off. The on/off switch can be held for 4 seconds in order to change the display from Fahrenheit (°F) to Celsius (°C), or from Celsius (°C) to Fahrenheit (°F). The on/off switch is also used to place the compass into a calibration or zone mode. For more information, refer to Compass Calibration and Magnetic Variance .