Windshield wiper system, function

D82.30-0050-79

Windshield wiper system, general

The windshield wiper system actuates the windshield wipe and wash function.

Windshield wiper, function

The windshield wiper system actuates the windshield wipe and wash function.

Function requirements, general

 Circuit 15R ON

 The status of circuit 15 is sent by the electronic ignition lock control unit (EZS) (N73/8) over the interior CAN (CAN B) to the SAM control unit (N10).

Wiping windshield, general

 The windshield wiping function keeps the windshield free of water or snow, for example.

The windshield wiper function is comprised of the following subfunctions:

 Intermittent wipe function sequence

 Wiper start suppression function sequence

 Function sequence of wiping at specified speed

 Single wipe function sequence

 Function sequence for interrupting wiping during engine start

 Function sequence for automatic speed reduction

 Function sequence for wipe stop

Intermittent wipe function sequence

The intermittent wipe function is activated by turning the combination switch (S4) to position "1" (rain sensor (B38/2b1) with low sensitivity) or to position "2" (rain sensor with high sensitivity).

 When changing the switch position of the combination switch from switch position "0" to "1" or "2" or when changing from switch position "1" to "2", a wipe cycle ("reaction wipe") is activated.

The steering column tube module (MRM) control unit (N80) reads in the switch position of the combination switch directly and send this over the suspension FlexRay (Flex E), EZS control unit and the interior CAN to the SAM control unit.

The SAM control unit sends the switch position of the combination switch over the rain and light sensor LIN (LIN B16) to the rain sensor in the rain and light sensor (B38/2).

Based on the position of the combination switch and the degree of wetness on the windshield, the rain sensor calculates the frequency of the required wiping cycles and sends the corresponding request over the rain and light sensor LIN back to the SAM control unit.

The SAM control unit then actuates the wiper motor (M6/1) accordingly.

The intermittent wipe function is interrupted under the following conditions:

 Activating wipe/stop function

 Activating wash function

 Activating single wipe function

 Activation of extended wiping function

 Activating wiper startup suppression function

 Turning combination switch to position "0", "3" or "4"

 Blocking wiper motor

 Missing or faulty rain sensor data

Additional function requirements for wiper start suppression

 Vehicle speed v < 3 km/h

 Combination switch in position "1" or "2"

Wiper start suppression function sequence

The wiper start suppression is intended to prevent the driver or front passenger from being sprayed with water from the windshield when getting in or out of the vehicle as the result of an initiated wipe operation. The windshield wipers remain in the park position despite a wipe request triggered manually or automatically. If a door is opened during a wipe procedure, the SAM control unit interrupts the actuation of the wiper motor.

To do this, the following variables are taken into account:

 Vehicle speed

 Switch position of the combination switch

 Status of doors

Vehicle speed:

The instrument cluster (A1) sends the vehicle speed over the user interface CAN (CAN HMI), EZS control unit and the interior CAN to the SAM control unit.

Switch position of the combination switch:

The steering column tube module (MRM) control unit reads in the switch position of the combination switch directly and sends this over the suspension FlexRay, EZS control unit and the interior CAN to the SAM control unit.

Status of doors:

The status of the driver's door is sent by the driver's door control unit (N69/1) over the interior CAN to the SAM control unit. The status of the front passenger door is sent by the front passenger door control unit (N69/2) over the interior CAN to the SAM control unit.

The SAM control unit reads in all relevant information, evaluates it and interrupts actuation of the wiper motor. A wiping procedure that has already started is not interrupted immediately. The wipers continue to move to the park position.

The wiper start suppression is deactivated under the following circumstances:

 Vehicle speed: v  3 km/h

 Combination switch in position "3" or "4"

 Single wipe or wash function activated

 Driver and front passenger door closed and gear range "D" or "R" engaged

 No information is sent from the fully integrated transmission control (VGS) electric controller unit (on model 907) or the electronic transmission control (EGS) control unit (on model 910) about the current drive range with "circuit 15R ON" over the drive CAN (CAN C), powertrain control unit (N127), suspension FlexRay, EZS control unit and the interior CAN to the SAM control unit. Instead, "Gear range N" is constantly sent. The current drive range is not available until "circuit 15 ON". The wiper startup suppression function is not canceled by "circuit15R ON" through the status of the gear range.

Function sequence of wiping at specified speed

The wipe function with predefined speed is activated by turning the multifunction switch to position "3" (continuous wipe at low speed) or position "4" (continuous wipe at high speed).

The steering column tube module (MRM) control unit reads in the switch position of the combination switch directly and sends this over the suspension FlexRay, EZS control unit and the interior CAN to the SAM control unit. The SAM control unit then actuates the wiper motor accordingly.

The wash function with predefined speed is interrupted under the following conditions:

 Activating wipe/stop function

 Activating wash function

 Activation of extended wiping function

 Activation of the speed reduction function

 Turning the combination switch to position "0", "1", or "2"

 Blocking wiper motor

Single wipe function sequence

The single wipe function can only be activated if the combination switch is set to position "0", "1" or "2". If the windshield wiper is not located in the rest position, the request of the combination switch is ignored.

The single wipe function is activated by pressing the combination switch up to the detent point.

Wipe once:

To wipe once, briefly push the combination switch axially to the detent point.

Repeated wiping:

If the combination switch is pressed for longer, wiping takes place in accordance with the duration for which it is pressed, but only for a maximum of t = 30 s.

The steering column tube module (MRM) control unit reads in the switch position of the combination switch directly and sends this over the suspension FlexRay, EZS control unit and the interior CAN to the SAM control unit.

The SAM control unit then actuates the wiper motor over the rain and light sensor LIN accordingly.

 If the combination switch is held in switch position “0” for longer than t = 30 s, a “stuck combination switch” is assumed and the single wipe function is interrupted despite the current request.

The speed at which the windshield wiper is moved during single wipe corresponds to the wiping speed in position "3" (continuous wipe at low speed).

The single wipe function is interrupted under the following conditions:

 Activating wash function

 Activation of extended wiping function

 Activating wipe interruption during engine start function

 Blocking wiper motor

Function sequence for interrupting wiping during engine start

During engine start, the SAM control inhibits actuation of the wiper motor. Any wiping procedure already started is terminated. The engine start is recognized by the transmission of the status of circuit 50. The status of circuit 50 is sent by the EZS control unit over the interior CAN to the SAM control unit.

Additional function requirements for automatic speed reduction

 Combination switch in position "3" or "4"

 Vehicle speed reduction from v > 6 km/h to v < 3 km/h

Function sequence for automatic speed reduction

It is assumed that the windshield does not become as wet at slow speeds.

For this reason, the SAM control unit reduces the wiper speed as soon as vehicle deceleration from v > 6 km/h to v < 3 km/h is detected.

The steering column tube module (MRM) control unit reads in the switch position of the combination switch directly and sends this over the suspension FlexRay, EZS control unit and the interior CAN to the SAM control unit.

The instrument cluster sends the vehicle speed over the user interface CAN, EZS control unit and the interior CAN to the SAM control unit.

The SAM control unit reads in all relevant information and switches the wiping speed of the wiper motor down by one stage.

The automatic speed reduction function of the windshield wiper system is interrupted under the following conditions:

 Activating single wipe function

 Activating wash function

Additional function requirements for wipe stop

 Wipe or wash function activated

Function sequence for wipe stop

The wipe stop function prevents the wiper motor from being actuated by the SAM control unit when the engine hood is open and thus causing damage to the vehicle. If the engine hood is opened at a speed of v < 3 km/h, the SAM control unit immediately stops actuation of the wiper motor. At a speed of v > 6 km/h, the wiper stop function is deactivated, i. e. the wiper motor is actuated again from this speed onwards.

The status of the engine hood is monitored by the following components that are read in directly by the SAM control unit:

 Engine hood switch (S62/51)

The steering column tube module (MRM) control unit reads in the switch position of the combination switch directly and sends this over the suspension FlexRay, EZS control unit and the interior CAN to the SAM control unit.

The instrument cluster sends the vehicle speed over the user interface CAN, EZS control unit and the interior CAN to the SAM control unit.

The SAM control unit reads in all relevant information, evaluates it and interrupts actuation of the wiper motor.

Windshield washer, function

The windshield wiper system actuates the windshield wipe and wash function.

Function requirements, general

 Circuit 15R ON

 The EZS control unit sends the status of "circuit 15" over the interior CAN to the SAM control unit.

Washing windshield, general

The washer fluid is pumped through the hoses to the wiper blades and sprayed directly in front of the wiper blades in accordance with the direction in which the wiper arms are moving. In other words, when the wiper arms move upwards, only the top part of the wiper blades is supplied with washer fluid.

In other words, when the wiper arms move downwards, only the lower part of the wiper blades is supplied with washer fluid. With its low washer fluid consumption, this optimizes the windshield cleaning process while also reducing the level of wiper blade wear.

P82.35-2673-75

The windshield wash function is comprised of the following subfunctions:

 Washing function sequence

 Extended wiping function sequence

 Function sequence for interrupting washing during engine start

 Function sequence for wash stop

Washing function sequence

The washing function is activated by pressing the combination switch in axial direction beyond the detent point.

The steering column tube module (MRM) control unit reads in the switch position of the combination switch directly and sends this over the suspension FlexRay, EZS control unit and the interior CAN to the SAM control unit.

The SAM control unit receives the request and actuates the windshield washer system pump (M5/1) directly as well as the wiper motor directly.

Depending on the direction in which the wiper arms are moving, only the upper or the lower side of each wiper blade is supplied with washer fluid. This is implemented by reversing the polarity on the windshield washer system pump.

During washing, wiping takes place with the wiper speed set on the combination switch or in stage "3".

The washing function is interrupted under the following conditions or aborted after t = 15 s:

 Activation of the washer interruption function when the engine starts

 Activating wipe/stop function

 "Combination switch stuck" detection

Extended wiping function sequence

The extended wiping function is activated as soon as the combination switch is no longer activated.

The number of extended wiping cycles depends on the combination switch actuation time.

 Actuation time t < 200 ms: Extended wiping does not take place.

 Actuation time t < 1 s: Extended wiping occurs once.

 Actuation time t > 1 s: Three extended wipes occur.

The SAM control unit sends the "extended wiping active" status over the rain and light sensor LIN to the rain sensor in the rain and light sensor. Wiping requests from the rain sensor during extended wiping are ignored.

Extended wiping takes place with the wiper speed set on the combination switch. When the combination switch is in the rest position, extended wiping takes place with speed "3".

The extended wiping function is interrupted or aborted under the following conditions:

 Activation of the washer interruption function when the engine starts

 Wiper motor blockage detection

 Activating wash function

 Activating wipe/stop function

Function sequence for interrupting washing during engine start

When the engine starts, the SAM control unit blocks the actuation of the windshield washer system pump.

Any wiping procedure that has already started is terminated.

The engine start is recognized by the sending of the "circuit 50" status. The status of "circuit 50" is sent by the EZS control unit over the interior CAN to the SAM control unit.

Function sequence for wash stop

The wash stop function prevents the windshield washer system pump from being actuated when the engine hood is open.

The status of the engine hood is monitored by the following component that is read in directly by the SAM control unit:

 Engine hood switch

If an open engine hood is recognized, the SAM control unit interrupts the windshield washer system pump actuation.

If the engine hood is closed, the windshield washer system pump can be actuated again.

This is also possible if the engine hood is open and the vehicle speed exceeds v = 6 km/h.

The instrument cluster sends the vehicle speed over the user interface CAN, EZS control unit and the interior CAN to the SAM control unit.