The electronic control of the power windows is via the door modules and the Car Access System (CAS) control module.
The power window motor contains an additional electronics unit with the load circuit for the electric motor as well as the final deactivation and antitrapping protection of the windows.
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 power windows are activated by means of a pulse-width modulated control signal that is evaluated by the electronics in the power window motor. This makes it possible that the power window can be operated with various motor speeds.
The Car Access System (CAS) control module contains the functions of the radio remote control, the ignition 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 CAS enables and disables the window operations depending on the terminal status, the status of the door contacts and the coding data. In addition, the convenience operation of the power windows is controlled by the CAS.
The switch block for the driver's door contains the switches and buttons for the following functions:
The switch block in the driver's door can be used for central operation of the windows of all doors. In addition, pressing the button for the child safety lock can disable operation of the rear power windows via the operating switches.
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 and rear power windows are operated by means of operating switches the passenger's doors, and these are connected to the relevant door module via two cables.
If roller sunblinds are fitted for the rear side and triangular windows, the rear doors contain switch blocks for operation of the windows and roller sunblinds instead of simple operating switches. A switch block is connected to the door module by a data line.
The power window motor consists of a direct current motor with reduction gears and an electronics unit.
The electronics unit consists of electronic power switches, power supply and a Hall sensor unit.
The electric motor is activated across the internal power switches in the electronics unit. The motor speed and direction of rotation are determined by the pulse-width modulated control signals from the door module.
The Hall sensor unit integrated in the electronics unit (two Hall sensors and one magnetic disc) is used by the door module to register the direction of rotation, the speed and position of the window. In addition, the voltage during motor operation is measured in the electronics unit and reported to the door module across a sensor wire. On the basis of the Hall sensor impulses and the voltage values, the door module can detect trapping or blocking in the system.
To enable the door module to determine the window positions and activate the antitrapping protection, an initialization procedure is required (see chapter on service functions in this functional description).
Activation of the power window motor via electronic power switches makes it possible to operate the motor in various speed stages.
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:
All power window switches 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 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.
Convenience closing and convenience opening make it possible to open and close all windows and the sliding sunroof, 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 CAS control module. The CAS issues the command for activation of convenience operation via CAN bus telegram to the four door modules and the sunroof module. With a time delay, the convenience operation is run in the following order:
The antitrapping protection does not protect against trapping between the window and door per se, but rather limits the maximum trapping force that can occur.
When the power windows are operated for the first time, there is an initializing procedure (see chapter on service functions) whereby the end positions of the windows and the necessary closing power are determined by the door module. As the mechanical forces continuously change due to the influence of temperature and aging, the changes in the closing power are also determined for each window operation after the initialization and thus the antitrapping protection is continuously adapted.
The antitrapping 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 antitrapping protection is always active when the is being closed. However, it can be overridden by the ”Emergency Close” function.
Note
So that the antitrapping protection functions reliably, the power windows must be reinitialized after every repair (see chapter on service functions).
This function is for deliberate closing of the windows without antitrapping 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 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 antitrapping protection is active in every button position.
In addition, coding can be used to set the following function familiar from the power window control used to date:
The child safety lock is enabled using the switch in the switch block of the driver's door and the signal is transferred to the CAS control module, where the status remains stored also after the ignition has been switched off. The CAS sends a bus telegram to activate the LED in the switch block so that the driver can see the current status of the child safety lock.
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.
Soft stop and soft start optimize the closing and opening characteristics of the power windows and reduce the closing noise.
To prevent overheat of the power window motors, each motor has its own motor protection calculated from the motor running time depending on the ambient temperature.
If the power window motor is operated too frequently within a certain time, it is disabled for a defined period. A movement that is running is not interrupted in this case.
To reduce the load on the battery, the power windows are not able to function at terminal 50 (starter motor). Every running action, e.g. opening, it terminated immediately and the power window is stopped. Following the startup operation, the windows have their full function when operated.
The voltage supply is monitored locally in the door modules. If the voltage supply is below 9 V or above 16 V, the power windows are disabled and any running action is aborted.
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. The initialization serves to adapt the antitrapping protection to the power window system. The initialization procedure is divided into the functions standardization and learning the characteristic curve.
In the case of standardization, the mechanical end stops of the power window are learned.
In the case of learning the characteristic curve, the mechanical closing forces in the power window are recorded.
The initialization must always by run with the power window switch on each door!
Control procedure for initialization:
Important!
It must be ensured that there is on-board supply voltage of at least 12 V during initialization, otherwise initialization of the power window is not possible.
The antitrapping 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, 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.