Windshield Washing and Wet Arm Heating

Windshield Washing And Wet Arm Heating

In the case of windshield washing, water is sprayed onto the windshield glass and then wiped away by the wiper.

The washer jets are integrated directly in the wiper arm so that also at high vehicle speeds the windshield glass is provided with sufficient water.

To ensure that the wash system also functions reliably at low outside temperatures, a heating wire is integrated in the water hose in the wiper arms (wet arm heating).

Brief description of components
Wiper module
The wiper module contains the electronics for controlling the wiper, the washer pump and the wet arm heating. It is connected to the K-CAN SYSTEM data bus. The wiper module is securely connected to the wiper motor.

Steering column switch center (SZL)
The steering column switch center registers the signals of the switches and sensors installed in the steering wheel. It also controls all the components located on the steering wheel and the steering column. Information is received and sent via the data bus BYTEFLIGHT.

The wiper switch is connected to the steering column switch center.

Wiper switch
The wiper stages intermittent wipe, stage 1 and stage 2 are selected with this switch. The washer pump is activated by pulling back the wiper switch.

The switch positions of the wiper switch are transferred from the steering column switch center via the data buses BYTEFLIGHT and K-CAN SYSTEM to the wiper module.

Washer pump
The washer pump pumps the water from the washer reservoir to the washer nozzles in the wiper arms. It is activated directly by the wiper module.

Wet arm heating
The wet arm heating consists of a heating wire integrated in the washer hose in the wiper arm. The heating wire is supplied with current by the wiper module.

Central Gateway Module (ZGM)
The central gateway module links the data buses
- BYTEFLIGHT
- K-CAN SYSTEM
- PT-CAN
- Diagnostic bus

Main functions

Windshield washer
Operating the wiper switch in the position "windshield wash" causes the wiper module to activate the washer pump and spray water through the washer nozzles in the wiper arms onto the windshield. Depending on the country, two different washing programs can be coded in the wiper module:

- Washing program 1
When the switch is operated, the washer pump is only activated when the wipers are moving upwards. The washer pump is disabled during the downwards movement of the wiper arms.

- Washing program 2
When the switch is operated, the washer pump is activated with full power when the wipers are moving upwards. For the downwards movement of the wiper, the power of the washer pump is reduced, so that only a little water is sprayed onto the windshield.

If the switch was operated for longer than one second, when it is released 3 more wiper cycles are carried out and the windshield is wiped dry (after-wipe program).

If the switch was operated for less than a second, there is no wiping dry.

Time monitoring
A higher level time monitor protects the washer pump against thermal overload.

If the washer reservoir is full, the washer pump is switched off after a maximum of 2 minutes by the time monitor.

If the level switch in the washer reservoir detects that the washer reservoir is almost empty, the washer pump is switched off after 15 seconds.

Wet arm heating
Depending on the outside temperature and battery voltage, as of terminal R On the wet arm heating is activated by the wiper module. When the wet arm heating is active, current flows through the heating wires in the water hose of the wiper arm. The heating wires warm up and thus warm the water in the water hose.

The heating wires are supplied with current by means of a pulse-width-modulated signal (PWM signal). This enables control of the heat output.

Service functions

Cleaning the washer jets
The function "Clean washer jets" is used to clean as well as check the washer nozzles. Following repair work, the function can be used to check the spray angle.

The cleaning function is triggered as follows:
- Switch off terminal R in the vehicle
- Within 1 minute, push the wiper switch upwards into the wash position and hold it in this position for 3 seconds.
- The washer pump is activated as long as the switch is pressed, but for a maximum of 30 seconds
- The activation of the washer pump is in cycles (2 seconds on, 1 second off), so that the water consumption is not too high.

If the switch is released, the activation can be repeated if the switch is again operated for at least 3 seconds the 'wash' position.