Electrical seat adjustment (ESA) - GF91.29-P-0009FLA

MODEL 212 without CODE 275 (Electrically adjustable front seats memory package) 

Fig 1: Electrical Seat Adjustment Block Diagram - Model 212 Without Code 275

Courtesy of MERCEDES-BENZ USA

Function requirements, general 

• Circuit 15R ON or run-on active
• No overvoltage or undervoltage

Run-on:

If circuit 15R is switched off, electric seat adjustment is only possible for another t = 180 s. 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 sends the status of circuit 15 via the interior CAN to the rear SAM control unit.

The door status is detected by the front door rotary tumbler switch. Each front door control unit directly reads in the status of the corresponding front door rotary tumbler switch and sends it to the rear SAM control unit via interior CAN.

Electrical seat adjustment (ESA), general 

The ESA enables the electrical adjustment of the driver and front passenger seat. The driver and front passenger seat can be adjusted as follows:

• Seat height
• Backrest angle
• Seat inclination

The ESA function comprises the following subfunctions:

• Function sequence for manual seat adjustment 
• Function sequence for antilock device 

Function sequence for manual seat adjustment 

For manual seat adjustment, the following switches must be pressed and held until the required position is reached:

• Driver seat partially electric seat adjustment switch
• Front passenger seat partially electric seat adjustment switch

Following this, the corresponding seat adjustment motor is actuated:

• Seat adjustment motor for height adjustment, driver seat or front passenger seat
• Seat adjustment motor for inclination adjustment, driver seat or front passenger seat
• Seat adjustment motor for backrest inclination, driver seat or front passenger seat

The power for the seat adjustment motors is supplied by the rear SAM control unit directly via the respective seat adjustment switch.

Function sequence for antilock device 

Since the electric seat adjustment does not have a sensor system or its own control unit, the antilock device is actuated by means of a thermal fuse in the seat adjustment motors. As a result, if the respective seat adjustment motor is blocked, it is not switched off until it exceeds a certain temperature threshold.