Hummer H2. Manual — part 729

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 mirrors
temperature range which 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:

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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.

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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.

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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.

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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.

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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 and Compass without OnStar(R)

The inside rearview mirror has 2 switches that perform the following functions:

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The MIRROR switch is used to enable or disable the automatic day-night feature of the mirror. With the
ignition in the ON position, depress the MIRROR switch 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 MIRROR switch.

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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 Variance Procedure .

2004 Hummer H2

2004 ACCESSORIES & EQUIPMENT Stationary Windows - Hummer H2

Switches of the Inside Rearview Mirror with the Automatic Day-Night Feature, Compass/Temperature Display without
OnStar(R)

The inside rearview mirror has 2 switches that perform the following functions:

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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.

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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
Variance Procedure .

Switches of the Inside Rearview Mirror with the Automatic Day-Night Feature with Compass and OnStar(R)

The inside rearview mirror has 4 switches that perform the following functions:

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The ON/OFF switch located at the left side of the mirror performs the following functions:

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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 4 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 4 seconds.

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To turn the compass ON and OFF - With the ignition in the ON position, depress the ON/OFF
switch to turn the compass ON. Depress the ON/OFF switch again to turn the compass OFF. 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 Variance Procedure .

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The 3 switches on the right side of the mirror are for OnStar(R) operation. For more information, refer to
OnStar Description and Operation in Cellular Communication.

Switches of the Inside Rearview Mirror with the Automatic Day-Night Feature, Compass/Temperature Display with
OnStar(R)

The inside rearview mirror has 4 switches that perform the following functions:

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The ON/OFF switch located at the left side of the mirror performs the following functions:

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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

2004 Hummer H2

2004 ACCESSORIES & EQUIPMENT Stationary Windows - Hummer H2

ON/OFF switch for 6 seconds.

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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 Variance Procedure .

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The 3 switches on the right side of the mirror are for OnStar(R) operation. For more information, refer to
OnStar Description and Operation in Cellular Communication.

COMPASS CALIBRATION AND VARIANCE PROCEDURE

Compass Calibration

Before calibrating the compass, drive the vehicle to an open area that is magnetically clean or free of large
metallic objects such as high tension power lines or large steel buildings. Verify there are no magnetized roof
antennas, magnets on or hanging from the mirror, or any other magnetized objects on the inside or outside of
the vehicle close to the mirror.

1. Start the engine.

2. Press and hold the switch for the compass, which may be depicted as COMP, COMPASS, or on/off

(w/UE1) depending on the type of mirror on the vehicle, until the letter "C" or "CAL" is displayed.

3. Drive the vehicle in circles at a speed of less than 8 km/h (5 mph) until the "C" or "CAL" is replaced by a

proper vehicle heading. The calibration procedure is now complete.

Compass Magnetic Variation Adjustment

Magnetic variation adjustments are required when the compass displays a constant error in heading. Variation is
the difference between magnetic north and true north due to geographical location.

IMPORTANT: Before calibrating the compass, make sure the mirror has the correct

zone number. Refer to Compass Magnetic Variation Adjustment.

2004 Hummer H2

2004 ACCESSORIES & EQUIPMENT Stationary Windows - Hummer H2

Fig. 45: World Magnetic Variation Map
Courtesy of GENERAL MOTORS CORP.

1. Locate your current geographic location on the World Magnetic Variation Map.

2. Turn ON the ignition, with the engine OFF.

3. Press and hold the switch for the compass, which may be depicted as COMP, COMPASS, or on/off

(w/UE1) depending on the type of mirror on the vehicle, until a zone number appears on the compass
display.

4. Depress the switch for the compass to select the desired zone number.

5. Wait 5 seconds. The display will return to a compass heading. The variance procedure is now complete.

6. Calibrate the compass. Refer to Compass Calibration mentioned above.

REAR WINDOW DEFOGGER DESCRIPTION AND OPERATION

Rear Window Defogger System Components

The rear window defogger system consist of the following components:

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HVAC control module

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Body control module (BCM)

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DEFOG relay

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Rear window defogger grid

Rear Window Defogger Operation

2004 Hummer H2

2004 ACCESSORIES & EQUIPMENT Stationary Windows - Hummer H2