Chevrolet 2007 Silverado 1500 Pickup Owner's Manual page 239

Sensors
The solar sensor, located in the defrost grille, that
is 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 an interior temperature sensor located
next to the steering wheel that measures the
temperature of the air inside your vehicle.
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