Hyundai sonata Owner's Manual page 264

Convenient Features
Fan speed control
The fan speed can be set to the desired
speed by using the fan speed control
toggle switch.
More air is delivered with higher fan
speeds.
Pressing the OFF button turns off the fan.
Information
For better sound quality, fan speed may
automatically slow down for a couple
of minutes when you activate voice
recognition or hands free.
NOTICE
Operating the fan when the ignition
switch is in the ON position could cause
the battery to discharge. Operate the
fan when the engine is running.
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Air conditioning
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Push the A/C button to manually turn
the air conditioning system on (indicator
light will illuminate).
Push the button again to turn the air
conditioning system off.
OFF mode
Push the OFF button of the front to
turn off the air climate control system.
However, you can still operate the mode
and air intake buttons as long as the
ignition switch is in the ON position.
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