Block Diagram
CAN abbreviations
| B86 | Rain sensor | Y105 | Washer pump, windscreen and rear screen |
|---|---|---|---|
| M17 | Wiper motor, windscreen | Y106 | Washer pump, headlamps |
| M17RR | Wiper motor, rear screen |
Functional Description
The UEC is responsible for the following wiper functions:
- Windscreen wipers
- Windscreen washer system
- Headlamp washer system
- Rear screen washer system
- Washer fluid level
The switch position of the screen wash/wipe system lever registered by the CIM, is transmitted to the UEC via the LSCAN. The UEC then activates the screen wiper or screen washer system in accordance with the CAN request.
Screen Wiper Park Position
The windscreen wipers are provided with a screen wiper park position switch. This information is registered by the UEC and transmitted to the REC via the LSCAN. The purpose of the park position switch is to stop the windscreen wipers in the park position, when the wiper function is switched off. This happens, as soon as the ignition key is turned to the "(terminal W)" or "OFF" position in the case of active wash/wipe function. The UEC supplies the wiper relay with voltage until this is achieved. The screen wipers can also be driven into a service position. This is achieved by turning the ignition key to the "(terminal W)" or "OFF" position and actuating the screen wiper lever (approx. 10 seconds) in the "interval" position.
Wiper Speed
The screen wiper system features the following operating states: single wipe, slow wiper speed, fast wiper speed and interval wiping. This is dependent upon the driver request registered in the CIM. The wiper lever actuation is registered by the CIM and transmitted to the UEC via the LSCAN. The UEC evaluates this information and actuates the wiper motor accordingly. In the case of "interval wiping", the UEC also requires the position of the wiper interval potentiometer on the steering column switch. If a rain sensor is installed, the wiper interval potentiometer position is used to adjust the sensitivity of the rain sensor signal (the REC transmits the information to the UEC via the CAN bus).
Rain Sensor
The REC receives information on the current rain intensity from the rain sensor. The rain sensor calculates this using the sensitivity set by means of the wiper interval potentiometer. The result is transmitted from the REC to the UEC via the LSCAN and is used to control the wiper interval. The rain sensor must be reactivated after each "ignition OFF", by activating the wiper interval function.
Screen Washer System
The switch status of the windscreen washer system and rear screen washer system registered by the CIM, is transmitted to the UEC via the LSCAN. The UEC actuates the appropriate washer pump on the basis of this information. If the windscreen wipers are already operating in the slow or fast wiper speed mode, the wiper speed is maintained if the windscreen washer system is actuated. If another function is active or was switched off, the slow wiper speed mode is activated automatically. If low beam or parking lights are switched on, the headlamp washer system is also activated by the UEC. The pump switches off automatically if it is actuated for more than 20 seconds.
Washer Fluid Level Sensor
The fluid level registered by the washer fluid level sensor is evaluated by the UEC and transmitted to the DIS via the LSCAN. If the UEC detects that the washer fluid level is too low, the rear screen washer function and the headlamp washer system are deactivated.
Rear Screen Wiper
The rear screen wiper is activated under the following conditions
- The rear screen wiper lever on the steering column is activated. This condition is evaluated by the CIM and transmitted to the UEC via the LSCAN.
- The windscreen wipers are activated and engaged reverse gear is simultaneously recognised. On the basis of information "Windscreen wipers activated" received from the CIM and the driving stage evaluated by the UEC, the UEC decides whether the rear screen wiper should be activated. This information is transmitted to the REC. The REC actuates the rear screen wiper relay accordingly.
Dry Wiping
At vehicle speeds of less than 30 km/h, the windscreen wiper and rear screen wiper are actuated again for a single wipe, approx. 4 seconds after the last wiping cycle.