Wiper Pressure Control Motor: Description and Operation
Windscreen Wiper Pressure Control (ADV/ZKE):Functional Description:
The windscreen wiper pressure control system (ADV) is controlled by the general module (GM) of the central body electronics (ZKE). The relays are located in the ADV module. Installation location: Rear power distribution box.
Operating Principle:
The contact pressure of the windscreen wiper arm on the driver's side is varied by a DC motor depending upon the vehicle speed.
After a speed of 5 km/h has been reached, the contact pressure control (ADV) begins to raise the windscreen wiper arm (increase in contact pressure). As the vehicle speed increases, the contact pressure is increased in stages. The speed stages are: 100 km/h, 140 km/h, 180 km/h.
The windscreen wiper returns to its initial position after switching off the ignition (wiper arm released).
The "wash" function results in an increase in the contact pressure also when the vehicle is stationary. When driving, the "wash" function increases the
contact pressure by one stage.
Installed in the contact pressure control motor (ADV) is a microswitch which is actuated by a cam wheel. The switch signals to the general module (GM) when
the relevant increase in contact pressure has been reached. The switch switches ground to the general module for as long as the ADV motor is running. When the windscreen wiper pressure control (ADV) reaches the corresponding increase in contact pressure, a cam of the cam wheel interrupts the ground connection and the motor stops.
Function Monitoring:
The general module uses the signal from the microswitch in the contact pressure control motor (ADV) for function monitoring. If no signal is received or if a ground signal is applied at the general module for too long, this situation is evaluated as a defect and the ADV motor is switched off by an active block
guard.
The two ADV relays in the contact pressure control module (ADV) are monitored via a diagnostic link. If one of the relays sticks the second relay is also
switched on (potential balance) in order to stop the ADV motor. The balance is canceled when the vehicle drives faster than 5 km/h and the ADV relays are in working order once again.
Important!
The potential balance is activated when the ADV module is removed and installed.
The potential balance is also active when the ignition is switched off. This results in increased closed-circuit current consumption (approx. 300 mA).
Automatic cut-out only takes place when the vehicle is driving.
Remove and install the ADV module only with its fuse removed.
Anti-Blocking Function:
As soon as the general module of the windscreen wiper pressure control (ADV) system detects a fault, it activates an anti-blocking function which switches off the ADV motor. The anti-blocking function is canceled automatically when the vehicle drives at a speed above 5 km/h and the fault is no longer pending. When the vehicle is stationary, the anti-blocking function can be canceled only by disconnecting the battery.