Mercedes-Benz GL Operator's Manual page 119

Driver's and front-passenger seat
Rear seats
The three red indicator lamps in the button
indicate the heating level you have selected.
The system automatically switches down
from level 3 to level 2 after approximately
eight minutes.
The system automatically switches down
from level 2 to level 1 after approximately ten
minutes.
The system automatically switches off
approximately 35 minutes after it is set to
level 1.
Make sure that the SmartKey is in position
X
1 or 2 in the ignition lock.
To switch on: press button : repeatedly
X
until the desired heating level is set.
To switch off: press button : repeatedly
X
until all the indicator lamps go out.
i
If the battery voltage is too low, the seat
heating may switch off.
Seats
117
Z