Windows: Description and Operation
Glass, Frames and Mechanisms
COMPONENT LOCATION
OVERVIEW
Electric windows are installed in all 4 doors. The front windows are controlled by their respective door modules integrated into the window switch packs. The rear windows are controlled by the GEM (generic electronic module). The GEM (generic electronic module) and the door modules communicate with each other on the P bus.
Window operating features are market dependent and include one-shot opening and closing, convenience opening and closing, and anti-trap. Market options for window operation are set centrally in the GEM (generic electronic module).
Individual window switches are installed in each of the 3 passenger doors. Window switches for all of the windows, and a child lock switch to isolate the rear windows, are installed in the driver's door.
All of the window switches have 2 switching positions in each direction. The first switching position operates the window in the inching mode, where the window moves until the switch is released or until it reaches the fully open or closed position. The second switching position operates the window in the one-shot mode.
WINDSHIELD
NOTE:
A heated windshield is not available on vehicles fitted with infra-red reflecting glass.
The laminated windshield is bonded, and sealed, to the body aperture using PU sealant. Heat bonded to the inner surface of the windshield is the optical unit for the rain/light sensor.
Tinted green, with an anti-glare strip, and infra-red reflecting glass available as an optional extra, the windshield has 2 separate heating systems.
Vertical fine-wire multi-strand elements are fitted between the glass laminations to de-ice and de-mist the windshield. At the bottom of the screen 6 horizontal heating elements bonded to the interior glass surface prevent the wiper blades freezing to the windshield during adverse weather conditions. For additional information, refer to Control Components
The windshield is supplied with the heating element flat foil connectors fitted to a molded sealed terminal block. This terminal block is wired to a connector for connecting to the vehicle harness.
The following should be noted when replacing the windshield:
- Ensure that the windshield is electrically disconnected
- Before and during fitting the windshield ensure that the heater elements foil connectors are taped back to avoid damage to the connectors
- Avoid excessive use of sealant. When correctly fitted the sealant bed should not exceed 5 mm in thickness.
REAR SCREEN
The rear screen is made from green tinted, tempered glass and is bonded to the upper tail door frame using PU sealant. Fitted to the inner surface of the rear screen are the heating elements and antenna for the audio system and central locking systems.
The heating element is connected by 2 lucar terminals while the antenna is connected to the vehicle by a 2-pin connector at the top of the screen.
The following should be noted when replacing the rear screen:
- Ensure that the screen is electrically disconnected.
- Avoid excessive use of sealant. When correctly fitted the sealant bed should not exceed 5 mm in thickness.
SIDE WINDOWS
Front Door Window Regulator
Rear Door Window Regulator
Cable operated window regulators powered by an electric motor are installed in each of the doors.
Anti-trap Sensors
An anti-trap sensor is installed along the top of each window aperture, just outside the travel path of the window glass. Each anti-trap sensor consists of a rubber covered contact strip connected to ground and to a power supply from the door modules(front windows) or GEM (generic electronic module) (rear windows). When the anti-trap sensor is pressed the resistance across the contact strip is reduced. If a window is being closed and the door module/GEM (generic electronic module) detects a drop in resistance across the associated anti-trap sensor, it immediately (in less than 20 milliseconds) reverses the window.
CONTROL DIAGRAM
NOTE:
A = Hardwired; B = K bus; C = Diagnostic DS2 bus; M = P bus
PRINCIPLES OF OPERATION
Electric window operation using the window switches is enabled while the ignition switch is in positions I and II, and for 16 minutes after switching from position I to position 0. Window operation is immediately disabled when a front door is opened.
When the switches in the driver's door are used to operate the passenger windows or the child lock, the DDM (driver door module) outputs a related message on the P bus. The passenger door module or the GEM (generic electronic module) respond to the message by operating the appropriate window or the child lock function. While the child lock is engaged, the GEM (generic electronic module) ignores inputs from the rear window switches, and the driver door module illuminates a LED (light emitting diode) in the child lock switch.
End of Travel Shut Off
End of travel shut off for the window motors is determined by monitoring the current draw of the motors. Each time it switches on a window motor, the door module or GEM (generic electronic module) measures the window motor current for 22 milliseconds, in 2 milliseconds intervals. The maximum value measured within that time is stored as the switch-on current, which must be 5 A minimum. When the window motor current next exceeds the switch-on current minus 2 A, the door module/GEM (generic electronic module) assumes the window has reached the end of its travel and, after 0.5 second, switches off the power supply to the window motor, even if a window switch is still being activated.
Measuring the switch-on current for each switching operation automatically compensates for changes of load with varying ambient conditions etc.
To protect the window motors from overheating if the end of travel shut off function fails, window motor activation in both directions is limited to 8 seconds.
Anti-trap
The anti-trap function is enabled for window closing in both the inching and one-shot modes. If an anti-trap sensor is activated while a window is closing, the window motor is reversed. The reversing time is proportionate to the preceding closing time and varies between 0.5 and 2.0 seconds.
In an emergency, for example if the anti-trap sensor is faulty, the anti-trap function can be overridden by holding the window switch in the one-shot closed position.
Convenience Opening and Closing
Convenience opening and closing is enabled provided the ignition switch is not in position I or above. The windows and roof opening panel (where fitted) can be opened and closed in sequence, while unlocking and locking the vehicle, using the driver's door lock or the remote handset.
Convenience closing begins after a time delay of 1.5 seconds when the door lock is held in the lock position or the remote handset lock button is pressed and held. The anti-trap function is enabled during convenience closing. The closing operation also stops immediately the door lock is released from the lock position or the remote handset lock button is released. The window motors are switched in pairs, with the rear ones switched first followed 1 second later by the front ones. The roof opening panel begins closing when all of the windows are closed or 3.5 seconds after convenience closing started, whichever occurs first.
North American Specification (NAS) vehicles leave the factory with convenience closing configured 'OFF'. This feature can be configured 'ON' using the customer personalization feature.
Convenience opening begins after a time delay of 2.5 seconds when the door lock is held in the unlock position or the remote handset unlock button is pressed and held. The opening operation stops immediately the door lock is released from the unlock position or the remote handset unlock button is released. The window motors are switched in pairs, with the front ones switched first followed 1 second later by the rear ones. The roof opening panel begins opening 3.5 seconds after convenience opening started.
Operating the windows and roof opening panel in sequence allows a degree of selective operation, e.g. the windows can be closed and the roof opening panel left open when locking the vehicle and using convenience closing.
Repetition Blocking
To prevent the window motors from overheating, the door modules and the GEM (generic electronic module) record the run time for each motor they control. The run time, in seconds, is added to a counter on completion of each activation, and 1 second is deducted from the counter for every 3 seconds the window motor is inactive. If the counter exceeds 60 seconds, no new activation for the window motor is accepted until the counter is below 60 seconds again. The only exception is a reversing operation triggered by the anti-trap function, which is always accepted regardless of the counter value.