Buick 2008 Lucerne Owner's Manual page 166

Sensors
The solar sensor, located in the defrost grille, in the
middle of the instrument panel, monitors the solar
radiation. Do not cover the solar sensor or the system
will not work properly.
There is also an interior temperature sensor located
next to the steering wheel that measures the
temperature of the air inside the vehicle.
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There is also an exterior temperature sensor located
behind the front grille. This sensor reads the outside air
temperature and helps maintain the temperature
inside the vehicle. Any cover on the front of the vehicle
could cause a false temperature reading to display.
In order to prevent false temperature readings at startup,
the displayed temperature will not change until the
following occurs:
•
Vehicle speed is above 10 mph (16 km/h) for
five minutes.
•
Vehicle speed is above 32 mph (51 km/h) for
two and a half minutes.
The climate control system uses the information from
these sensors to maintain your comfort setting by
adjusting the outlet temperature, fan speed, and the air
delivery mode. The system may also supply cooler
air to the side of the vehicle facing the sun. The
recirculation mode will also be used as needed to
maintain cool outlet temperatures.