Cadillac CTS - Manual (Page 183)

Sensors
There is a solar sensor located on the instrument
panel, near the windshield.
There is also an interior
temperature sensor
located to the right of
the steering wheel
on the instrument panel.
These sensors monitor the solar radiation and the
air inside your vehicle, they use the information
to maintain the selected temperature by adjusting
to the temperature, the fan speed, and the air
delivery system. The system may also supply
cooler air to the side of the vehicle facing the sun.
The recirculation mode will also be activated,
as necessary. Do not cover the sensors or
the automatic climate control system will not
work properly.
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