Mercedes-Benz 2008 M-Class Operator's Manual page 221

Controls in detail
3-zone automatic climate control*
220
1 Temperature control, left
2 Air distribution and air volume
(automatic, manual)
3 Air distribution, driver's side
4 Front defroster
5 Increasing air volume
6 Rear window defroster
7 Air distribution, passenger side
8 Rear automatic climate control
on/off
> USA only
™ Canada only
9 Temperature control, right
a Automatic climate control on/off
b Air distribution, passenger side
c Air distribution, passenger side
d AC cooling on/off
Residual heat/ventilation
e Display
f Decreasing air volume
g Air recirculation
h Air distribution, driver's side
j Air distribution, driver's side
k Interior temperature sensor
l Adopting driver's side settings for all
zones