Roller sun blind, function - GF68.50-P-0004RF

Model 205 with code 540 (Electric sunblind for rear window)

Fig 1: Roller Sun Blind Block Diagram

Courtesy of MERCEDES-BENZ USA

Function requirements, general

Circuit 15R ON
No overvoltage or undervoltage
Overheating protection not activated
The minimum temperature is available (outside temperature greater than value set via diagnosis or interior temperature T ≤ 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 operating the rear window roller sun blind button in the left lower control panel, 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 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".

The rear window roller sun blind motor is equipped with two Hall sensors. The signals from the Hall sensors are read in and evaluated by the rear SAM control unit.

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. It is necessary to normalize the roller sun blind before the first operation or in the following cases:

Replacement of the rear SAM control unit
Denormalization of the roller sun blind, e.g. due to limp-home mode or undervoltage)

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.

When the rear window roller sun blind button is pressed for longer than t = 15 s, the roller sun blind is denormalized. This function can be deactivated via the diagnosis tester.

In order to start normalization manually, the rear window roller sun blind button must be pressed and held until the end of the actuation. The rear window roller sun blind is actuated with reduced speed until the mechanical limit stop is reached and switched off by the blockage detection. 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 audio/COMAND control unit reads in the status of the rear window roller sun blind button via the LIN keypad and transmits this via the telematic CAN, head unit, user interface CAN, electronic ignition lock control and interior CAN to the rear SAM control unit. The rear SAM control unit actuates the rear window roller sun blind motor directly.

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 in the left lower control panel, the roller sun blind can be extended or retracted manually. The audio/COMAND control unit reads in the status of the rear window roller sun blind button via the LIN keypad and transmits this via the telematic CAN, head unit, user interface CAN, electronic ignition lock control and interior CAN to the rear SAM control unit. The rear SAM control unit actuates the rear window roller sun blind motor directly. 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 722, 724, 725).

Vehicles with transmission 716:

Engaging the reverse gear is recorded by the manual transmission main shifter shaft position sensor. The CDI control unit or the ME-SFI control unit reads in the signal of the manual transmission main shifter shaft position sensor directly and transmits the signal "Reverse gear engaged" to the electronic ignition lock control unit via the drive train CAN, the powertrain control unit and the chassis FlexRay.

Vehicles with transmission 722, 724, 725:

Gear range "R" is engaged through the fully integrated transmission control unit. The fully integrated transmission control unit then sends the status of the gear range via drive train CAN, powertrain control unit and the chassis FlexRay to the electronic ignition lock control unit.

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 t = 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-2052-97FBA
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