Hummer H2. Manual - part 259

z

Use the urethane adhesive caulking kit for replacement of any urethane adhesive-installed window using 
the Full Cut Method. 

You may use an equivalent urethane adhesive system if the system meets GM Specification GM 3651M. 
Always follow the system manufacturer's instructions for application, handling, and curing. 

AUTOMATIC DAY-NIGHT MIRROR DESCRIPTION AND OPERATION 

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: 

z

Inside rearview mirror  

z

Ambient air temperature sensor  

Power and Ground of the Inside Rearview Mirror 

z

With the ignition ON, ignition voltage is supplied to the mirror from the IGN E fuse in the underhood 
fuse block.  

z

Ground for the mirror is provided by G302.  

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 face 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 rear of the mirror or windshield side. The ambient light sensor 
is used to determine the exterior light conditions. With a low exterior light condition detected, and a high light 
condition from behind of the car, 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 exterior 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. The mirror monitors this input to disable the automatic day-
night feature. This allows the driver to see objects in the mirror clearly when backing up, even during the night. 

Compass 

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 earths 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 

 

2004 Hummer H2 

2004 ACCESSORIES & EQUIPMENT Stationary Windows - Hummer H2

  

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: 

z

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.  

z

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.  

z

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.  

z

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.  

z

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: 

z

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.  

z

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: 

z

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.  

z

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: 

z

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 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.  

{

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 .  

z

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: 

z

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 

 

2004 Hummer H2 

2004 ACCESSORIES & EQUIPMENT Stationary Windows - Hummer H2

  

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 Variance Procedure .  

z

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