Mercedes-Benz 2011 GL-Class Operator's Manual page 130

Windshield wipers
128
X
For safety reasons, you should remove the
key from the ignition lock.
or
X
Switch off the engine using the Start/Stop
button and open the driver's door.
X
Remove the cause of the obstruction.
X
Switch the windshield wipers back on.
The windshield wipers are not working
The windshield wiper drive is malfunctioning.
X
Select another wiper speed on the
combination switch.
X
Have the windshield wipers checked at a
qualified specialist workshop.