GF91.29-P-2018GM Folding 3RD Seat Row, Function

GF91.29-P-2018GM Folding 3rd Seat Row, Function
- with CODE (845) 3rd seat row folding down electrically

General function requirements
^ Circuit 30
^ Vehicle speed ≤ 12 km/h
^ Rear-end door or right rear door open and
^ Folding backrest in park position switch detected

General function description of folding over 3rd seat row
By actuating the front switch for left folding backrest (S158/1), front switch for right folding backrest (S158/3), rear switch for left folding backrest (S158/2) or rear switch for right folding backrest (S158/4), the right or left folding backrest of the 3rd seat row in the rear can be electrically folded in or out, respectively.

Folding over the 3rd seat row makes the following subfunctions possible:
^ Folding in or out electrically
^ Locking monitoring
^ Blockage detection

Folding in or out electrically
Operation of the folding backrest switches is read in by the folding rear bench seat control unit (N32/26). The folding rear bench seat control unit checks whether the backrest is locked or unlocked. If the backrest is locked, the left backrest release unit (A93/1) or right backrest release unit (A93/2) is actuated.

If the backrest is unlocked, the left folding backrest motor (M53/10) or right folding backrest motor (M53/11) is actuated by the folding rear bench seat control unit.

If the folding backrest switches for the left and right seats are operated simultaneously, the right seat is actuated first. After the maximum actuation time (approx. 0.4 s) of the unlocking motor in the right seat backrest release unit, the left seat is actuated.

On vehicles up to production period 31.12.08, the corresponding switch for folding backrest must be held while the backrest is folded over. On vehicles as from production period 01.01.09, a brief operation (one-touch operation) of the switch for the folding backrest suffices and the backrest fold automatically to the end stop.

The release unit end position switches and the unlocking motors are integrated in the left backrest release unit and the right backrest release unit.

The end position of the folded seat is recorded by a limit position switch in the left backrest release unit and the right backrest release unit. This limit position switch can be used to record two possible positions: "seat raised" and "seat lowered".

Behavior with several switch operations
If the other switch is operated for the same seat after operating a folding backrest switch, the first function is aborted. The second adjusting function does not start. Adjustment does not continue until it has been detected that both switches are in the park position.

Stuck switch detection:
- Switch signal > 20 s

If a switch for the folding backrest is detected as being stuck, the corresponding channel is then blocked. Functions requested by the stuck switch will not be performed until the park position has been detected.

Abort conditions
The function is aborted or interrupted if:
- The respective switch for the folding backrest is released (only for vehicles up to 31.12.08) or
- the backrest is detected as locked (unlocking switch open) and the time difference between the opening of the unlocking switch and the end of backrest motor actuation is too great, or
- the maximum actuation time of the folding backrest motor has been reached (18 s), or
- blocking is detected or
- the other switch for the same seat is actuated.

Locking monitoring
The end position switches in the backrest release unit are used to monitor the backrests. If a backrest is detected as unlocked, the folding rear bench seat control unit transmits a message to the instrument cluster (A1). The following messages are displayed on the instrument cluster:
- LEFT BACKREST OF 3RD SEAT ROW NOT LOCKED"

or

- "RIGHT BACKREST OF 3RD SEAT ROW NOT LOCKED"

Lockup recognition
In order to prevent damage to the seat mechanism, the actuation time of the folding backrest motors is limited. This is done by evaluating the Hall sensor signal in the motor concerned. If the signal width is greater than the blocking detection time, blocked status is detected and the relevant folding backrest motor is shut off.

After blocking has been detected in a particular direction, motorized adjustment can take place again by actuating in the same direction. The folding backrest motors are also protected from overheating using a thermo switch.