Mercedes-Benz C-Class Operator's Manual page 146

Air vents
144
Setting the air vents
Example
: Side window defroster vent
Side air vent, left
;
Control for left side air vent
=
To open or close: turn thumbwheel = to the
X
left or right as far as it will go.
To adjust the air direction: hold side air
X
vent ; by thumbwheel = and move it up or
down or to the left or right.