Electric Power Sliding Roof, Function - GF77.20-P-0007RF

Model 205, 253 

with code 414 (Sliding sunroof) 

Courtesy of MERCEDES-BENZ USA

Function requirements, general 

• No overvoltage or undervoltage
• Consumer shutoff not active
• Transport mode not activated

Sliding roof, general 

The sliding roof function allows the sliding roof to be opened and closed. Operation occurs by means of the roof system switch in the overhead control panel control unit. The sliding roof is a combined sliding/tilting roof. The sliding roof function drops the sliding roof down and moves it backwards into the headliner; the power tilting roof function raises the sliding roof at the rear.

There are comfort functions for opening and closing the sliding sunroof, which enable the sliding sunroof and side windows to be opened and closed centrally from a control point.

Overheating protection:

The sliding roof system motor is not designed for continuous operation. A overheating switch integrated in the sliding roof motor protects the sliding roof motor against overload.

The sliding roof motor is switched off if the maximum permissible operating time is exceeded.

If the overheating protection function was triggered, actuation is disabled for the minimum cooling time. The overheating protection function does not operate during roof reversal (after a blockage is detected).

The sliding roof function comprises the following partial functions:

• Normalize sliding roof 
• Position monitoring and blockage detection 
• Open/close sliding roof 
• Automatic reserving function 
• Rain closing 

Additional function requirements for normalizing the sliding sunroof 

• Sliding roof denormalized
• Circuit 15R ON or run-on time active (up to 5 min after circuit 15R OFF, where front doors are closed)

The electronic ignition lock control unit sends the status of circuit 15 via interior CAN to the sliding roof control module.

The left front door control unit directly reads in the status of the left front door rotary tumbler switch and transmits it to the sliding roof control module via the interior CAN.

The right front door control unit directly reads in the status of the right front door rotary tumbler switch and transmits it to the sliding roof control module via the interior CAN.

Normalize sliding roof 

Normalizing is the basis for assigning the current position to the position of the sliding roof sensed by the sliding roof control module. For this purpose the sliding roof must be completely opened.

Completely open sliding roof using roof system switch until the mechanical end stop is reached. Then reactuate roof system switch for min. 1 s. The sliding sunroof control module detects the blockage by evaluating the signals of sliding sunroof Hall sensor 1 and sliding sunroof Hall sensor 2. The corresponding location counter is set to zero.

When normalized, the sliding roof system motor is switched off by the sliding roof module before the mechanical stop is reached during automatic opening and closing.

Denormalization is performed under the following conditions:

• If circuit 30 is OFF during actuation of sliding sunroof motor.
• If the sliding sunroof exceeds the defined movement range
• If one of two Hall sensors fails for 10 signal edges
• If both Hall sensors fail to supply signals for longer than 320 ms when reversing.
• If sliding roof is actuated in the event of undervoltage.

The position of the sliding roof cannot be determined in the denormalized condition. The function is then restricted to manual closing and opening in increments of 0.5 s each.

Additional function requirements for position monitoring and blockage detection 

• Active actuation of sliding roof

Position monitoring and blockage detection 

The sliding roof control module monitors the position of the sliding roof by evaluating the signals from the following sensors:

• Hall sensor 1, sliding roof
• Hall sensor 2, sliding roof

The Hall sensors are arranged offset by 90° on the axis of the sliding roof motor. The position of the sliding roof is determined by counting the Hall sensor pulses. The position "Sliding roof in tilt position" is defined as zero position. The zero position is set by normalization. Blockage is detected if no Hall sensor signals are detected during an adjustment for a period of 350 ms. If the blockage is recognized in the closing direction, the sliding roof motor is first stopped and then actuated in the opposite direction. If the blockage is recognized in the opening direction, the sliding roof motor is stopped and no longer actuated.

Additional function requirements for opening/closing sliding roof 

• Circuit 15R ON or run-on time active (up to t = 5 min after circuit 15R OFF, with front doors not yet open)

The electronic ignition lock control unit sends the status of circuit 15 via interior CAN to the sliding roof control module.

The left front door control unit directly reads in the status of the left front door rotary tumbler switch and transmits it to the sliding roof control module via the interior CAN.

The right front door control unit directly reads in the status of the right front door rotary tumbler switch and transmits it to the sliding roof control module via the interior CAN.

Open/close sliding roof 

The sliding roof can be opened and closed manually or automatically. The sliding roof is opened or closed manually for the time the request is active by actuating the roof system switch to the first catch.

The sliding roof is fully opened or closed automatically by actuating the roof system switch beyond the first catch.

Automatic adjustment is aborted if the roof system switch is actuated again. The automatic reversing function is active during closing.

The overhead control panel control unit directly reads in the status of the roof system switch. For vehicles up to model year 2019, the overhead control panel control unit transmits the status to the sliding sunroof control module via the roof LIN, front SAM control unit, and interior CAN. For vehicles as of model year 2019, the overhead control panel control unit transmits the status to the sliding sunroof control module via the interior CAN. The sliding roof control module actuates the sliding roof motor according to the selected actuation direction for the time the request is present.

When the sliding sunroof is denormalized, it can only be actuated in steps of 0.5 s each.

Recognition of switch signals:

The actuation of the roof system switch is only clearly detected after 40 ± 10 ms. The max. actuation time is 20 s. After 60 s, the system considers the roof system switched to be jammed. A new actuation (triggered via the roof system switch) can only be performed again after detecting that the roof system switch is in the rest position.

Additional function requirements for automatic reversing function 

• Sliding roof NORMALIZED
• Valid reference data present for automatic reversing function

Automatic reserving function 

The automatic reversing function is based on a comparison between the current power consumption of the sliding roof motor and the power consumption recorded during a teach-in run or adaptation. If this difference exceeds a certain limit value during a closing operation, this is detected as a pinching of the overhead control panel control unit.

Teach-in run:

During a learn-in run all of the sliding roof closing procedures are accomplished in the normalized condition. The sliding sunroof control module adapts a change in the power consumption of the sliding sunroof motor resulting from increased sluggishness (e.g. dirt in the mechanical system).

If a blockage is detected during an opening procedure, the sliding roof is stopped. During a closing procedure, the sliding roof is stopped and then reversed (moved in the opposite direction).

Special case, manual closing:

If the roof system switch is actuated again in the closing direction within 2 s after the roof is reversed, greater force is applied to close the roof. The next attempt deactivates the automatic reversing function.

Additional function requirements for rain closing 

• Circuit 15R OFF or vehicle locked
• Sliding roof open in slide position

The circuit 15 status and the central locking status are sent by the electronic ignition lock control unit over the interior CAN to the sliding roof control module.

Rain closing 

The sliding roof is moved to the tilt position when it starts to rain. Moistening the windshield is recognized by the rain/light sensor with additional functions. The rain/light sensor with additional functions reads in the signals from the rain sensor directly and evaluates them. Then, it transmits the "rain closing function" request to the sliding sunroof control module via the rain and light sensor LIN, front SAM control unit, and interior CAN. The sliding roof control module then actuates the sliding roof motor. The sliding roof is moved to the tilt position. Monitoring is then no longer performed.

The rain closing function is performed even if the run-on time (6 h) has expired or the voltage or temperature is no longer within the range of the rain sensor.

Model 205, 253

with code 414 (Sliding sunroof)

with code 882 (Interior motion sensor)

Alarm triggering by the interior protection is suppressed during rain closing to prevent unintentional triggering of the anti-theft alarm system.