E92596
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Description
Item
Raindrop
1
LED
Comments:
(transmitter diode)
2
Lens
3
Photodiode
Comments:
(receiver diode)
4
Light loss due to deflection
5
The LED emits a beam of light with a known
intensity. The emitted beam emerges through the
lens and is then reflected by the windshield.
The reflected light beam enters back through the
lens and then reaches the photodiode. The
corresponding value taken without moisture on the
windshield is used as the reference value for
automatic calibration.
Subsequent deviations from this value cause the
windshield wipers to be switched on.
If precipitation falls on the windshield, part of the
light beam is deflected. This reduces the intensity
of the light reflected by the windshield. This loss
of intensity is registered by the photodiode and
reported via an LIN signal to the BCM (Body
Control Module).
When the automatic wipe function is switched on
(window wash/wipe lever set to intermittent wiping)
the wipers are only activated automatically if the
rain sensor registers water on the windshield.
The sensitivity of the rain sensor can be changed
by adjusting the window wiper rotary switch.
• Window wiper rotary switch at the top corner:
high sensitivity
– The wipers wipe even if only a small amount
of water has been measured on the
windshield.
• Window wiper rotary switch at the bottom
corner: low sensitivity
– The wipers only wipe if a large amount of
water has been measured on the windshield.
The rain sensor is self-calibrating.
The rain sensor supplies LIN signals with values
between 0 and 7 to the BCM (Body Control
Module).
Meaning of signals from rain sensor:
• Signal "0": window is dry.
• Signal "1-5": Windshield is damp. The BCM
activates normal wiping.
• Signal "6-7": Windshield is receiving severe
precipitation. The BCM activates the fast wipe
speed whenever the signal value is greater than
4.
Front windshield wiper motor
The front windshield wiper motor is a DC motor
with 3 brush type contacts. One brush type contact
is for ground and one is for normal wiping speed.
The third brush type contact is activated for high
wiping speed.
The integrated home switch is directly connected
to the BCM (Body Control Module). The home
switch contacts are open in all wiper motor
positions except the home position. When the
home switch contacts are open, the wiper motor
remains switched on even if a signal from the
steering wheel module requests that the wipers
stop. In home position, the home switch contacts
create a ground connection. The BCM recognizes
this ground connection and switches the wiper
motor off.
Rear wiper motor
The rear windshield wiper motor is a DC motor with
2 brush type contacts. It is controlled by a voltage
supply.
The integrated home switch is directly connected
to the BCM (Body Control Module). The home
switch contacts are closed in all wiper motor
positions except the home position. When the
G1079966en
501-16-
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Wipers and Washers
501-16-
8
DESCRIPTION AND OPERATION
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