Inside Rearview Mirror with the Automatic Day-Night Feature System Components
The inside rearview mirror with the automatic day-night feature system consists
of the following components:
| • | Ambient air temperature sensor |
Power and Ground of the Inside Rearview Mirror
| • | With the ignition ON, ignition voltage is supplied to the mirror from
the ISRV fuse in the underhood fuse block. |
| • | Ground for the mirror is provided by G304. |
Inside Rearview Mirror with the Automatic Day-Night Feature System Operation
The inside rearview mirror uses 2 photocell sensors. One sensor is
the headlight sensor, located on the rear side of the mirror. The headlight sensor
is used to determine light conditions present at the mirror face. The other sensor
is the ambient light sensor, located on the front of the mirror or windshield side.
The ambient light sensor is used to determine light conditions present at the mirror.
With automatic day-night feature enabled, the mirror uses ambient light sensor
to determine the exterior light condition. With a low light condition detected,
and a high light condition from behind at the headlight sensor, the inside rearview
mirror will automatically darken the face of the mirror.
In the daytime, the mirror is in a normal state because of the high light
condition that is indicated by the ambient light sensor. With the gear selector
lever in the REVERSE position, backup lamp supply voltage is supplied as an input
to the inside rearview mirror. In night time conditions only, the mirror monitors
this input to disable the automatic day-night feature which allows the face to
gradually change to a normal state. This allows the driver to see objects in the
mirror clearly when backing up.
Compass
The mirror uses two 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.
Temperature Display
The inside rearview mirror monitors the ambient air temperature sensor. As the
outside air temperature gets warmer, the ambient air temperature sensor will lower
resistance. The inside rearview mirror monitors this change and will show this as
a warmer temperature on the display. Temperatures exceeding 62°C (143°F) will
be out of the mirror's temperature range and SC will be shown on the temperature
display. In colder outside air temperatures, the ambient air temperature sensor will
raise in resistance. The inside rearview mirror will show a colder temperature on
the display. Temperatures lower than -40°C (-40°F) will be out of the mirror's
temperature range and OC will be shown on the temperature display. In cold temperatures
such as 3°C (37°F) or below, the temperature display will show ICE when the
ignition is first turned on. The display will toggle between ICE and the actual outside
temperature until the temperature update process is complete.
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, 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. |
Switches of the Inside Rearview Mirror with the Automatic Day-Night Feature,
Compass/Temperature Display without OnStar®
The inside rearview mirror has two switches that perform the following functions:
| • | The TEMP switch is used to turn the compass/temperature display on or
off, It is also used to enable or disable the automatic day-night feature of the
mirror. With the ignition in the ON position, depress the TEMP switch to enable
the compass/temperature display. Depress the TEMP switch again to disable the
compass/temperature display. The TEMP 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). Depress the TEMP switch
until the green indicator illuminates on the mirror. This indicates that the automatic
day-night feature is enabled. To disable the automatic day-night feature of the
mirror, depress the TEMP switch until the green indicator turns off. |
| • | The COMP switch is used to turn the compass/temperature display on or
off. With the ignition in the ON position, depress the COMP switch to turn the
compass/temperature display on. Depress the COMP switch again to turn the compass/temperature
display 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. |
Switches of the Inside Rearview Mirror with the Automatic Day-Night Feature,
Compass/Temperature Display with OnStar®
The inside rearview mirror has four switches that perform the following functions:
The On/Off switch located at the left side of the mirror performs 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. |
