Mercedes-Benz 2013 GLS Class - Manual (Page 111)

Driver's and front-passenger seat
The three red indicator lamps in the button
indicate the heating level you have selected.
The system automatically switches 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 20 minutes after it is set to
level
1.
X Turn the key to position 1 or 2 in the ignition
lock ( Y page 157).
X To switch on: press button : repeatedly
until the desired heating level is set.
X To switch off: press button : repeatedly
until all the indicator lamps go out.
i If the battery voltage is too low, the seat
heating may switch off.
Seats
109
Seats, steering wheel and mirrors
Z