The windshield wash/wipe system is controlled by the GEM. To do this, the GEM primarily uses the signal from the window wash/wipe switch.
Secondary signals include the signals from the combined rain sensor/light sensor and the reverse gear switch (vehicles with manual transmission) ortheTCM (vehicles with automatic transmission).
The front windshield wash/wipe system will only run if the ignition is switched on.
Four wipe functions are available:
The position of the window wash/wipe switch is transmitted to the GEM. The GEM then controls the wiper motor via relays and sets the wiper speed.
Normal wipe speed remains available in the event of failure of the GEM.
The wiping functions work as follows:
If short wipe is requested, the GEM activates a relay until the request is cancelled. The front windshield wiper wipes at normal speed.
See wiping function - "Normal speed".
If normal speed wiping is requested, the GEM activates a relay. This applies a voltage to the switching contacts of a second relay. This second relay controls normal and high-speed wiping. For normal speed the second relay remains switched off. The voltage is fed through the second relay to the window wiper motor brush contacts for normal speed.
If high speed wiping is requested, the GEM activates both relays. The activated first relay conducts the current to the switching contacts of the second relay. The activated second relay conducts the voltage to the window wiper motor brush contacts for high speed.
If intermittent wiping is requested, the GEM activates and deactivates the first relay at the required interval according to the rotary switch position. The second relay stays switched off.
Time interval at level 1 = 1 second
Time interval at level 2 = 3.5 seconds
Time interval at level 3 = 6 seconds
Time interval at level 4 = 9.5 seconds
Time interval at level 5 = 15.5 seconds
Time interval at level 6 = 22 seconds
With this wiping function, the GEM uses the LIN (local interconnect network) signals from the rain sensor. The rain sensor supplies LIN signals with values of between 0 and 7. Refer to the rain sensor component description for details.
If the GEM fails, normal speed and a wiping interval of 3.5 seconds are available.
When the front windshield washer system is operated, the GEM activates the front windshield washer system relay. The windshield washer pump is supplied with power. The ground connection for the washer pump is provided by the deactivated rear window washer system relay. Both relays are integrated into the GEM. The GEM delays wiper operation for 100 ms after operation of the window wash/wipe switch. If the window wash/wipe switch is not held in the "on" position for at least 100 ms, then the GEM does not switch on the wiper. The GEM activates the windshield wiper for as long as the windshield washer system switch is operated.
The windshield washer pump is switched off after 10 seconds. When the switch is released, the GEM allows the windshield wiper to wipe a further 2 or 3 times.
This additional wiping function allows the front wiper blades to wipe once for 4 seconds after the last wiping movement to remove any remaining water from the windshield.
The additional wiping function is activated if:
The controller for returning the windshield wipers to their home position is integrated into the front windshield wiper motor. This ensures that the windshield wiper motor is returned to its home position if the windshield wiper is switched off before completing a wiping movement.
The rear windshield wash/wipe system will only run if the ignition is switched on.
The front and rear windshield wash/wipe systems use a shared window washer pump and cannot be used simultaneously.
Depending on the wiper speed of the front wipers, the rear wipers run with a delay interval of 6 seconds, 10 seconds or continuously. The time interval is controlled by the GEM.
The rear windshield wiper is switched on if:
The GEM actuates the rear window wiper motor. The windshield wiper runs in intermittent mode.
The GEM switches on the rear window washer system. The windshield washer pump is supplied with power. Reversing the polarity of the pump enables the washing fluid to flow to the rear washer jets instead of the front washer jets. The GEM activates the windshield wiper for as long as the windshield washer system switch is operated. The window washer pump is switched off after a maximum of 10 seconds. When the switch is released, the GEM allows the windshield wiper to wipe a further 2 or 3 times.
The GEM actuates the rear wiper motor until the gear lever is moved to neutral.
The headlamp washer system is only active when the windshield washer system is operated, if the headlamps are on at the same time (dipped beam).
The dipped beam can be selected using the light switch or the "automatic driving light" function.
Electrical control is performed by the R9 relay. The relay is controlled by the GEM.
If the sensor for the window washer system fluid level reports that the fill level in the window washer reservoir is low, then the headlamp washer pump can no longer be activated until the washer reservoir has been topped up again. At the same time, "window washer fluid level low" is displayed on the instrument cluster.