Cadillac 2006 XLR Owner's Manual page 146

To adjust the HUD so you can see it properly, do the
following:
1. Adjust the seat to a comfortable driving position.
If you change your seat position later, you may
have to re-adjust your HUD.
2. Start your engine and press the top or bottom of the
HUD button to center the HUD image in your view.
The HUD image can only be adjusted up and down,
not side-to-side.
3. Press the DIMMER button until the DIC reads HUD
DIMMING. Then use the brightness button to adjust
the desired intensity.
The brightness of the HUD image is determined by the
light conditions in the direction your vehicle is facing
and where you have the HUD set. If you are facing a
dark object or a heavily shaded area, your HUD
may anticipate that you are entering a dark area and
may begin to dim.
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To turn off the HUD, press the brightness button down
until the image disappears.
Polarized sunglasses could make the HUD image
harder to see.
As light shines out from the HUD, it is possible for light
to shine back in. In rare occurrences, when the sun
is at a specific angle and position, the sun's rays can
shine back into the HUD. When this occurs, the display
device within the HUD will be temporarily illuminated.
The event will end when the vehicle's angle to the
sun changes.
Clean the inside of the windshield as needed to remove
any dirt or film that reduces the sharpness or clarity
of the HUD image.
To clean the HUD, spray household glass cleaner on a
soft, clean cloth. Wipe the HUD lens gently, then dry
it. Do not spray cleaner directly on the lens because the
cleaner could leak into the unit.