Cadillac 2003 CTS Owner's Manual page 226

Interior Temperature Sensor
While the climate control system is in AUTO, the
system uses both the interior temperature sensor and the
electronic solar sensor to automatically adjust the
temperature and airflow in the vehicle. See "Electronic
Solar Sensor" following for more information. Be sure
not to cover the sensor with anything. If you do, the
automatic climate control system will not work properly.
This sensor
monitors the interior
temperature of the
vehicle. It is located to
the right of the
steering wheel on the
instrument panel.
Electronic Solar Sensor
This sensor monitors the sun's solar radiation. It is located
on top of the instrument panel near the windshield.
While the climate control system is in AUTO, the system
uses the information collected by the electronic solar
sensor to automatically adjust the temperature and airflow
to maintain your comfort. The climate control system may
supply cooler air to one side of your vehicle, if that side is
facing the sun. Be sure not to cover the sensor on top of
the instrument panel. If you do, the automatic climate
control system will not work properly.
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