Roller Sun Blind, Function - GF68.50-P-0004FG

Model 213.0/1 

up to model year 2021 

with code 540 (Electric roller blind for rear window) 

Courtesy of MERCEDES-BENZ USA

Function requirements, general 

• Circuit 15R ON
• No overvoltage or undervoltage
• Overheating protection not activated
• Minimum temperature present (outside temperature higher than value set by diagnosis or interior temperature above 1°C)

The electronic ignition lock control unit sends the status of circuit 15 over the interior CAN to the rear SAM control unit.

The instrument cluster sends displayed outside temperature via user interface CAN, electronic ignition lock control unit and interior CAN to the rear SAM control unit.

The climate control unit sends the current value of the interior temperature to the rear SAM control unit over the interior CAN.

Roller sun blind, general 

The roller sun blind is located in front of the rear window and can be extended and retracted vertically. By actuating the rear window roller sun blind button or rear window roller sun blind switch (model 213.1 with code 297 (Roller sun blinds in rear doors)), the roller sun blind can be extended or retracted manually. Depending on the status of the reverse gear, the roller sun blind is automatically extended or retracted.

The extended roller sun blind offers the following comfort for the passenger in the rear:

• Sightproofing
• Protection against excessive thermal radiation

The roller sun blind is driven by the rear window roller sun blind motor. Two Hall sensors are integrated into the rear window roller sun blind motors for position sensing.

The function includes a soft start-up and delaying of the roller sun blind in a defined range in front of the corresponding mechanical stop to reduce wear to the roller sun blind mechanism as well as noise development. This function is called "Soft stop".

Overheating protection:

Every time the rear window roller sun blind motor is actuated, it is counted in the rear SAM control unit. If a defined threshold value is exceeded within a fixed time, the rear SAM control unit switches off the rear window roller sun blind motor to prevent overheating. New actuation is only possible after a cooling phase stored in the rear SAM control unit. The rear SAM control unit additionally evaluates the inside temperature. The climate control unit sends the current value of the interior temperature to the rear SAM control unit over the interior CAN.

The roller sun blind function comprises the following partial functions:

• Function sequence for normalization 
• Function sequence for extending and retracting roller sun blind 
• Function sequence for lockup recognition 

Function sequence for normalization 

Normalization is the basis for the assignment of the current position to the position of the sun roller blind recorded by the rear SAM control unit. Normalization must be performed at the time the car is put into service and in the denormalized state. When normalizing the roller sun blind, the upper and lower mechanical end stop of the roller sun blind is actuated and the corresponding position of the rear SAM control unit is stored.

By actuating the rear window roller sun blind switch (model 213.1 with code 297 (Roller sun blinds in rear doors)) or rear window roller sun blind button for longer than 15 s, the roller sun blind is denormalized. This function can be deactivated via the diagnosis tester.

Denormalization is started by pressing and holding down the rear window roller sun blind switch (model 213.1 with code 297 (Roller sun blinds in rear doors)) or rear window roller sun blind button. The roller sun blind is extended or retracted and switched off at reduced speed until the mechanical stop is reached. The location counter of other limit stop is set to zero. The normalization process is triggered when the function is activated again.

During the subsequent actuation of the rear window roller sun blind motor, the rear SAM control unit defines the adjustment range of the roller sun blind by counting the Hall sensor signals. Another blockage detection takes place at the mechanical end stop of the target position.

The maximum adjustment range is stored in the corresponding location counter in the rear SAM control unit. Normalization is terminated.

The roller sun blind is normalized automatically after moving 100 times in normal operation or after lockup.

Function sequence for extending and retracting roller sun blind 

The roller sun blind can be extended and retracted manually or automatically.

Manual extension or retraction 

• By operating the rear window roller sun blind button:
  • Vehicles with transmission 716 or transmission 725 and except engine 177, 256, 276:

    The audio/COMMAND control panel (except code 446 (Touchpad only)) or touchpad (with code 446 (Touchpad only)) reads in the status of the rear window roller sun blind button via UBF-LIN and transmits it via telematic-CAN, head unit, user interface CAN, electronic ignition lock control unit and interior CAN to the rear SAM control unit. The rear SAM control unit actuates the rear window roller sun blind motor and directly reads in the signals from the Hall sensors. The roller sun blind is then extended and retracted.

  • Vehicles with engine 177, 256, 276:

    The front SAM control unit reads in the status of the rear window roller sun blind button over the instrument panel LIN and sends it over the interior CAN to the rear SAM control unit.

    The rear SAM control unit actuates the rear window roller sun blind motor and directly reads in the signals from the Hall sensors. The roller sun blind is then extended and retracted.

• By actuating the rear window roller sun blind switch (model 213.1 with code 297 (Roller sun blinds in rear doors)):

  The rear door control unit reads in the status of the rear window roller sun blind switch via the rear door LIN and transmits it to the rear SAM control unit via the interior CAN. The rear SAM control unit actuates the rear window roller sun blind motor and directly reads in the signals from the Hall sensors. The roller sun blind is then extended and retracted.

Automatic extension or retraction 

Depending on the status of the reverse gear, the roller sun blind is automatically extended or retracted. The request for retracting the roller sun blind is generated by engaging the reverse gear (transmission 716) or gear range "R" (transmission 725).

The reverse gear engaged status is defined as follows:

• Vehicles with transmission 716:

  The engaged reverse gear is recognized via the manual transmission main shifter shaft position sensor. The drivetrain control unit reads in the status of the manual transmission main shifter shaft position sensor directly and sends the signal "Reverse gear engaged" via chassis FlexRay to the electronic ignition lock control unit.

• Vehicles with transmission 725:

  The request to "Engage gear range R" is defined by the corresponding selector lever position. The fully integrated transmission control unit sends the transmission selector lever position to the electronic ignition lock control unit via drive train CAN, the powertrain control unit and the chassis FlexRay.

  The electronic ignition lock control unit uses the incoming information to generate the "Reverse gear engaged" status that is independent of the transmission variant and sends it via interior CAN to the rear SAM control unit. The rear SAM control unit then actuates the rear window roller sun blind motor in the retraction direction. The roller sun blind is retracted.

  After ending reverse travel, the roller sun blind is automatically extended, if it has been retracted automatically beforehand. Ending reverse travel is recognized if one of the following conditions are met:

• Reverse gear is recognized as "not engaged" for a specified time.
• Vehicle drives forward with a specified minimum speed.
• The engine is switched off.

  The instrument cluster sends the information on the vehicle speed via user interface CAN, electronic ignition lock control unit and interior CAN to the rear SAM control unit.

  The electronic ignition lock control unit sends the status of circuit 15 over the interior CAN to the rear SAM control unit.

  The rear SAM control unit then actuates the rear window roller sun blind motor in the direction of "extend". The roller sun blind is extended.

  The roller sun blind can be stopped during extending and retracting in each position for test purposes. For this purpose the actuation of the rear window roller sun blind motor can be interrupted manually or via diagnosis tester. To stop the roller sun blind manually, the rear window roller sun blind button must be pressed three times within 0.5 s. The rear SAM control unit then interrupts the actuation of the rear window roller sun blind motor. The roller sun blind remains in the current position.

Function sequence for lockup recognition 

Lockup is recognized, if the Hall sensor signals are missing for a preprogrammed time during extending and retracting.

The Hall sensor signals of the rear window roller sun blind motor are read in directly by the rear SAM control unit.

If blockage is detected, actuation of the rear window roller sun blind is stopped and then reversed.

	Electrical function schematic for roller sun blind		PE68.50-P-2052-97DBA
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