Power Windows, Function - GF72.29-P-0001FR

Model 257, 290 

up to model year 2021 

Courtesy of MERCEDES-BENZ USA

Function requirements, general 

• No overvoltage or undervoltage
• Circuit 15R r circuit 15 ON o run-on time active

Run-on: 

If terminal 15R is switched off, the power windows can still be operated for 5 min. If, during the run-on time, the circuits status or the door status is changed, the run-on time starts again.

The electronic ignition lock control unit transmits the circuit status of circuit 15 to the front door control units and rear door control units via the interior CAN.

The front door control units sense the status of the front doors (open or closed).

Power windows, general 

The side windows of the vehicle can be opened and closed electrically.

Operation possibilities:

• Driver-side power window and outside mirror adjustment switch group
  • Left front power window switch
  • Right front power window switch
  • Left rear power window switch
  • Right rear power window switch
• Passenger-side power window switch
• Left rear power window switch
• Right rear power window switch

Press and hold down power window switch to perform a manual function. To start an automatic function it is sufficient to momentarily actuate beyond the catch point. Actuation takes place for as long (maximum 25 s) as the corresponding request is pending or until the side window reaches the lower or upper stop.

Operation via controls in the rear can be inhibited via the rear side window child safety lock switch.

The priority of possible functions depends on their requirement. A command with higher priority is performed if a function with lower priority is currently active. A lower priority function is interrupted first and is accomplished only after the second valid request. If a command with lower priority is still present after completion of an operation request with higher priority, the former command is ignored. It is first necessary for the controls to recognize non-actuation of the lower priority request before the corresponding function can be activated.

Priority sequence:

1. Driver-side power window and outside mirror adjustment switch group
2. Remaining power window switches
3. Actuation via diagnostic tester
4. Close side windows via PRE-SAFE®
5. Open side window with crash ventilation
6. Comfort opening/closing via central locking
7. Convenience opening/closing via recirculated air function

The power window functions comprise the following partial functions:

• Normalizing 
• Manual raising and lowering 
• Automatic raising and lowering 
• Short stroke 
• Actuation by PRE-SAFE® 
• Crash ventilation 
• Excess force limiter 
• Lock-up reverse 
• Overheating protection 
• Childproof locks 

Normalizing 

Normalization is the basis for assigning the momentary positions to the positions sensed by the corresponding front door control unit and rear door control unit of the side window. To this end, the relevant side window must be fully closed manually, and the power window switch must continue to be pressed for approx. 300 ms. When the power window switch is then released, the side window lowers approx. 20 mm. The side window must now be closed fully once more within 4 s and the power window switch held for another 300 ms.

The corresponding signal path is described in the chapter "Manual run-up/run-down".

The location counter in the relevant front door control unit or rear door control unit is set to 0 and normalization is completed. In order to define the position of the side windows, the front or rear door control unit evaluates the current ripple of the power window motor that occurs during the rotation The counter status is increased when opening and decreased when closing the side windows.

The ratio between counter status and armature rotations of the power window motor is 4: 1.

The power windows are denormalized under the following conditions:

• Position counter status greater than maximum adjustment range
• Position counter status going beyond zero point tolerance for stored zero point
• No change in position detectable despite activation

The reason for denormalization is stored in the corresponding front door control unit and rear door control unit. When the power windows are denormalized, only the manual raising and lowering functions are possible.

Normalization is a basic requirement to use the entire power window functions.

Additional function requirements for manual raising and lowering 

• Child safety lock switched off (for rear side window control points

Manual raising and lowering 

Actuate and hold down corresponding power window switch until the first catch point in the "Opening" or "Closing" direction. Actuation lasts as long (maximum 25 s) as the corresponding request is pending or until the lower or upper stop is reached.

Front driver side window 

The left front door control unit reads in the status of the left front power window switch in the power window switch group and driver-side outside mirror adjustment via the left door LIN. The left front door control unit then actuates the left front door power window motor.

Front passenger side window 

• The right front door control unit reads in the status of the passenger-side electrical power window switch directly. The right front door control unit then actuates the left front door power window motor.
• The left front door control unit reads in the status of the right front power window switch in the power window switch group and driver side outside mirror adjustment via the front left door LIN and transmits it to the right front door control unit via interior CAN. The right front door control unit then actuates the left front door power window motor.

Rear side window 

• The rear door control unit reads in the status of the relevant electrical power window switch directly. The corresponding front door control unit then actuates the rear door power window motor.
• The left front door control unit reads in the status of the electrical rear power window switch in the electrical power window and the driver-side outside mirror adjustment switch group via the left front door LIN and transmits it to the rear door control unit via the interior CAN. The corresponding front door control unit then actuates the rear door power window motor.

Additional function requirements for automatic raising and lowering 

• Power windows normalized
• Child safety lock switched off (for rear side window control points

Automatic raising and lowering 

The corresponding power window switch must be actuated just beyond the first catch point in the "opening" or "closing" direction and then released.

The remaining function sequence corresponds to that of manual raising and lowering.

Actuation of the power window motors is discontinued automatically upon reaching the bottom or top stop. The automatic reserving function is active during automatic raising.

additional function requirements for short stroke 

• Power windows normalized

Short stroke 

When a door is opened, the side window is lowered to the short stroke position (approx. 4 mm). After closing the door, the side window is closed again completely.

The front door and rear door control units record the status of their door, and activate the relevant power window motor directly.

Additional function requirements for actuation by PRE-SAFE® 

• Power windows normalized
• Side windows opened further than PRE-SAFE® position

Actuation by PRE-SAFE® 

If the Electronic Stability Program detects an unstable vehicle status (e.g. understeer or oversteer), the side windows are closed to a defined position (50 ± 4 mm before upper stop) to minimize the risk of injury.

The electronic stability program transmits the information for the PRE-SAFE® status and the request for PRE-SAFE® adjustment via chassis FlexRay, electronic ignition lock control unit and interior CAN to the front door control units and rear door control units. The corresponding front door control unit then actuates directly the front door power window motor. The corresponding front door control unit then actuates directly the rear door power window motor.

Actuation by PRE-SAFE® is interrupted in case of:

• Active automatic reversing function
• Blockage detection
• Request via corresponding power window switch

Additional function requirements for crash ventilation 

• Front power windows normalized
• Front side windows closed more than 50 ± 4mm before upper stop

Crash ventilation 

Smoke particles are produced in the vehicle interior when the pyrotechnical restraint equipment is triggered. To ensure that these smoke particles are removed quickly, the front side windows are automatically opened to a defined position (50 ± 4mm before upper stop) in event of an accident.

The supplemental restraint system control unit sends the crash signal over the user interface CAN, electronic ignition lock control unit and interior CAN to the front door control units. The front door control units then actuate the front door power window motors directly.

The crash ventilation is interrupted:

• Blockage detection
• Request via corresponding power window switch

The crash ventilation is inhibited when the PRE-SAFE® function is activated.

Additional function requirements for excess force limiter 

• Window position in the range from 3 to 230 mm (clear opening)
• Power windows normalized

Excess force limiter 

The excess force limiter function operates when the window is raised automatically or manually, however, at different sensitivity levels (escalation stages). The power consumption of the power window motor serves as a reference for excessive force.

The system is designed adaptively to prevent mechanical sluggishness being evaluated as pinching. This means that the system recognizes sluggishness by the increased power consumption of the respective power window motor, and calculates an additional force of 10 N for the next request. This ensures a constant speed when opening or closing the power windows even in the face of advanced wear or external influences such as moisture and ice.

Adaption is limited to a maximum value of 80 N. The individual escalation stages depend on the operating request and background and are shown in the table below.

Manual closing	1. Actuation (escalation stage 1)	2nd actuation (escalation stage 2)	3rd actuation (escalation stage 3)
Holding power window switches	Stop at 100 N (+15 N)	Stop at 130 N (+15 N)	Actuation remains active
Releasing power window switches	Reverse 20 mm (+5 mm)	Reverse 20 mm (+5 mm)	Actuation stopped
Automatic closing
Releasing power window switches	Stop at 60 N (-10 N); Reverse 125 mm (+5 mm)	Stop at 80 N (-10 N); Reverse 125 mm (+5 mm)	Only manual raising possible

If the power window switch is actuated again within 2 s after reversing is finished, the status changes. If the power window switch is actuated again after a time of 2 s, escalation stage 1 (1st actuation) is started. If pinching is recognized during automatic raising triggered by the comfort closing function via the air recirculation function, the corresponding front door control unit or rear door control unit starts with escalation stage 1 (1st actuation).

If pinching is recognized during automatic raising, actuated by the KEYLESS-GO function (with CODE 889 (Keyless-Go)) or the closing side window function by PRE-SAFE®, the corresponding front door control unit or rear door control unit starts with escalation stage 2 (2nd actuation).

If power windows are not normalized, the excessive force limiter is active starting at a pinching force of 100 N. The side window always reverses when it runs into the upper seal.

On power windows which have not been normalized, the excess force limiter is deactivated within a short time after two closing requests. This allows normalization at the upper stop.

Mechanical vibrations caused by bad road conditions are not recognized as pinching and do not lead to reversal of the corresponding power window. The "bad road recognition" required for this purpose is therefore activated starting at a speed of 8 km/h.

Additional function requirements for lock-up reversing 

• Power windows normalized

Lock-up reverse 

If the respective front door control unit or rear door control unit does not detect any change in the position within 150 + 20 ms or detects a force increase of 160 N over the distance traveled, this is evaluated as a blockage. Closing is stopped immediately and the side window is opened 20 mm. The lock-up reversing function depends on the type of rolling up.

Escalation stages for excess force limiter function apply.

Overheating protection 

The protection of the power window motors is guaranteed by a thermal protection software in the corresponding front door control unit or rear door control unit. The software simulates temperature characteristics depending on the operating time. The parameters required for this were determined in tests and are stored in the associated front door control unit or rear door control unit.

The permissible ambient temperature range of the power window motors is: -40°Cto+85°C.

Childproof locks 

When the child safety lock is switched on, the rear side windows cannot be opened and closed by actuating the rear power window switch. Actuations already activated are interrupted immediately by the rear power window motors. The child safety lock can be switched on and off via the rear side window child safety switch in the power window switch group and driver side outside mirror adjustment.

The left front door control unit reads in the status of the rear side window child safety lock switch via the left front door LIN and sends it via the interior CAN to the rear control unit.

The rear side window child safety lock switch signals the driver that the child safety lock is activated via an integrated LED. For this purpose, the left front door control unit transmits the request to actuate the LED to the rear side window child safety switch via the left front door LIN.

If the position of the rear side window child safety lock switch can no longer be read with certainty, the child safety lock function is regarded as permanently switched on.

	Function schematic for power windows		PE72.29-P-2050-97XBA
	Overview of system components for windows and sightproofing		GF67.00-P-9999FR