The electronic control of the power windows is via the door modules and the Car Access System (CAS) control module.
The power window mechanism is driven by an electric motor. The electric motor is fitted with an integrated electronics unit. The electronics unit contains the load circuit for the electric motor and it controls the final shutdown and the anti-trapping protection of the power window mechanism.
The door modules register the signals of the switches and sensors installed in the doors and control the drives installed in the doors. Information is received and sent via the K-CAN PERIPHERALS data bus.
The electric motor of the power window mechanism is activated with pulse-width modulated signals. This makes it possible to operate the motor with different motor speeds and to reduce or increase the speed when raising or lowering or the windows.
The Car Access System (CAS) control module contains the functions of the radio remote control, the ignition and starting switch, the terminal control and the immobilizer. It is also the gateway module between the data buses K-CAN SYSTEM and K-CAN PERIPHERALS.
The Car Access System (CAS) enables and disables the window operations depending on the terminal status, the status of the door contacts and the coding data. The convenience operation of the power windows is also controlled by the Car Access System (CAS).
Operated from the switch block in the driver's door:
The switch block for the driver's door is connected to the driver's door module by a data line. All the switch information is transferred exclusively across this data line.
The passenger's door switch (BFT) only operates the power window of the passenger's door.
The power windows in the left and right rear doors are operated using the rear door switch.
The power window motor consists of a direct current motor with flanged-on reduction gears and an integrated electronics unit.
The electronics unit consists of electronic power switches, power supply and a Hall sensor unit.
The electric motor is activated across the power switches in the electronics unit. The motor speed and direction of rotation of the electric motor are determined by the pulse-width modulated control signals from the door module.
The power windows can be operated as of ignition lock position R (radio position).
After the ignition has been switched off, the power windows are deactivated:
Activation of the power window motor via PWM signals makes it possible to operate the electric motor at various speeds. Changing the motor speed influences the speed of movement of the windows. The windows are moved as follows:
All power window switches for the front windows have two switch positions in both operating directions. In the first switch position, the window is opened or closed as long as the switch is operated.
In the second switch position (switch pressed or pulled beyond engaging point), the front window is automatically opened or closed completely, also when the switch is released. This function is referred to as one touch opening and/or one touch closing. In one-touch operating mode, the power window mechanism runs at increased speed.
The automatic procedure is interrupted immediately when the power window switch is moved again in any direction.
One-touch operation can be partially disabled (only closing or opening) or fully disabled by coding. Statutory regulation mean that one-touch operation is not enabled in all country versions.
The Hall sensor unit integrated in the electronics unit (two Hall sensors and one magnetic disk) is used by the door module to register the direction of movement, the speed of movement and position of the window.
While the motor is running, the electronics unit measures the voltage on the electric motor. The voltage value is reported across a sensor wire to the door module. On the basis of the Hall sensor impulses and the voltage values, the door module can detect trapping when the window is closing or blocking in the drive system.
To enable the door module to determine the window positions and activate the anti-trapping protection, an initialization procedure is required (see service functions).
Convenience closing and convenience opening make it possible to open and close all windows, even from outside the vehicle. Convenience operation can be run using the remote control or the mechanical key.
Convenience closing is activated when after locking/securing the central locking system the key on the remote control remains pressed and/or the mechanical key is kept in the door lock in the position ”lock”.
In the same way, convenience opening is activated using the remote control key ”unlock” or door lock position ”unlock”.
The drives are activated after a brief waiting period.
The function is controlled in the Car Access System (CAS) control module. The Car Access System (CAS) issues the command for activation of convenience operation via CAN bus telegram to the four door modules. The convenience operation first activates the rear power windows and then the front power windows.
The anti-trapping protection does not protect against trapping between the window and door frame. However, this function limits the trapping force to a maximum permitted level.
When the power windows are operated for the first time, there is an initializing procedure (see service functions) whereby the end positions of the windows and the necessary closing power are determined by the door module. As the closing power continuously changes due to the influence of temperature and aging, continuous adjustment is required. To this end, even after initialization, the closing power is determined for every operation of the power windows and the anti-trapping protection is adapted to the changes.
The anti-trapping protection is activated when on closing the window the closing power exceeds a defined value. The closing operation is then interrupted immediately and the window is briefly moved towards 'open'.
The anti-trapping protection is always active when the is being closed. However, it can be overridden by the ”Emergency Close” function.
Note So that the anti-trapping protection functions reliably, the power windows must be reinitialized after every repair (see service functions).
This function is for deliberate closing of the windows without anti-trapping protection. It might be necessary to use this function, for example, in the event of an attack or if a window is frozen in place.
The control procedure of emergency closing is divided into two phases:
As of a vehicle speed of ≥ 16 km/h, emergency closing does not function.
If the child safety lock (KiSi) is switched on, Emergency Close can only be activated by the switch block in the driver's door.
Emergency Close can be disabled by coding. This means the anti-trapping protection is active in every button position.
In addition, the following functions can be set with coding:
The child safety lock (KiSi) is activated and deactivated with the KiSi button in the switch block on the driver's door. The status change is transferred to the Car Access System (CAS) control module, where the status remains stored also after the ignition has been switched off. By means of a bus telegram, the Car Access System (CAS) activates the red LED in the KiSi button. The current status of the child safety lock (KiSi) can be seen from the lit or unlit LED.
When the child safety lock is switched on, the following operations are no longer possible using the switches in the rear of car interior:
The child safety lock can only be disabled if the key is engaged in the ignition lock.
The soft stop and soft start functions optimize the closing and opening characteristics of the power windows and reduce the closing noise.
To prevent the power window motors from overheating, each electric motor features its motor protection circuit. The shutdown point for the electric motor is calculated from the motor running time depending on the ambient temperature.
If the power window motor is activated too frequently within a certain period, the power stage in the electronics unit is deactivated for a defined time. A movement that is running is not interrupted in this case.
To reduce the load on the vehicle electrical system battery, the power window functions are deactivated at terminal 50 (starting motor). Every running action, e.g. opening, is terminated immediately and the power windows are stopped. After the start operation, the power window functions can be used once again.
The supply voltage is monitored in the door modules. If the voltage supply is ≤ 9 V or ≥ 16V, the power window functions are blocked and all running actions are canceled.
Following replacement of a power window motor or a door module and following every repair to the power window mechanical system, an initialization must be carried out to adjust the anti-trapping protection to the power window system.
The sequence of initialization is subdivided into:
Standardization: In the case of standardization, the door module learns the mechanical limit stops of the power window.
Learning the characteristic curve: When learning the characteristic curve, the door module learns the mechanical closing forces in the power window.
Note: The initialization must always be run with the power window switch on each door!
Initialization procedure:
NB: The anti-trapping protection has no function during the entire initialization procedure.
If there is no valid characteristic curve, the one touch closing function is unavailable. If there is no standardization has been carried out, the Automatic Open function is also disabled. In this case, the window only moves around 2 cm in the desired direction with each press of the button.