The rain sensor monitors the amount of water on the windshield and automatically starts the windshield wipers. Rain sensor sensitivity can be adjusted using the thumb wheel on the right-hand steering wheel lever.

Right-hand steering wheel lever.
 Rain sensor button
 Rain sensor button
 Thumb wheel, sensitivity/interval 
wiper speed
 Thumb wheel, sensitivity/interval 
wiper speed
When the rain sensor is activated, the
 rain sensor symbol will be displayed 
in the instrument panel.
 rain sensor symbol will be displayed 
in the instrument panel.
Activating the rain sensor
When the rain sensor is activated, the engine must be running or the ignition in mode I or II while the windshield wiper lever is in position 0 or in the single sweep position.
Activate the rain sensor by pressing the rain sensor button
 .
.
Move the lever downward for an extra wiper sweep.
Turn the thumb wheel upward for increased sensitivity and downward for decreased sensitivity. The wipers will make one extra sweep when the thumb wheel is turned upward.
Deactivate the rain sensor
Deactivate the rain sensor by pressing the
 rain sensor button or moving the lever 
upward to another wiper mode.
 rain sensor button or moving the lever 
upward to another wiper mode.
The rain sensor is automatically deactivated in ignition mode 0 or when the engine is switched off.
The rain sensor is also automatically deactivated when the wiper blades are put in the service position. The rain sensor will reactivate when service mode is switched off.
CAUTION
The windshield wipers may start inadvertently and be damaged in automatic car washes. Deactivate the rain sensor when the engine is running or when the ignition is in mode I or II. The symbol in the instrument panel will go out.
 Wiper blades and washer fluid. Using the windshield wipers
Wiper blades and washer fluid. Using the windshield wipers Activating and deactivating the rain sensor's memory function
Activating and deactivating the rain sensor's memory function