Mercedes-Benz 2004 C-Class Wagon Operator's Manual page 174

Controls in detail
Audio system
Balance
Regardless of operating mode, press
the AUD key repeatedly until
appears on the display.
Press or key to shift sound accord-
L R
ingly to the left or right speakers.
or
Press both L and R keys simultaneously
to reset the Balance to its center level.
174
Returning audio functions to factory
settings
BALANCE
Regardless of operating mode, press
and hold AUD key longer than two
seconds. RESET
display.
All settings for bass, treble and balance
are returned to the center level and the
volume is set to a predefined level.
Audio system sound selection (EXT)*
Regardless of operating mode, press
the
The sound settings menu appears on
the display.
Press the
will appear on the
Press one of the function keys.
AUD key.
key.
EXT