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Seat heater (SIH), function - GF91.30-P-0003MCU

MODEL 451.3 /4 with CODE (S17) Seat heaters (FFO) 

Fig 1: Seat Heater (SIH) Function Diagram
G07077541Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

General information 

With the integrated seat heater, it is possible to heat the seat cushions and backrests in two heating stages. The heated cushions are heated until they reach the defined maximum temperature. The maximum energizing time depends on the interior temperature. At level 2, the energizing takes place with a higher heat output than at level 1. The maximum temperature is therefore reached more quickly at level 2.

The function status is indicated by two light-emitting diodes that are integrated in the heated seat switches.

Operating keys and switches 

Function requirements: 

Switch on seat heater (2nd stage) 

The 2nd stage of the seat heater is activated by a one-time actuation of the heated seat switch. At the same time, the heated seats control unit measures the interior temperature (once only) using an integrated temperature sensor.

The heated seats control unit energizes the respective heated cushion in heat-up mode at maximum output.

The duration of the actuation in heat-up mode depends on the measured interior temperature.

Then the heated cushion is actuated in continuous heating mode at 50 % of the maximum output.

Switch on seat heater (1st stage) 

The 1st stage of the seat heater is activated by actuating the heated seat switch twice.

At the same time, the heated seats control unit measures the interior temperature (once only) using an integrated temperature sensor.

The heated seats control unit energizes the respective heated cushion in heat-up mode at reduced output.

The duration of the actuation in heat-up mode depends on the measured interior temperature.

Then the heated cushion is actuated in continuous heating mode at 15 % of the maximum output.

IMPORTANT Because of the lower maximum output at level 1, the heated cushion is actuated for a longer period in heat-up mode compared to level 2.

Switch over seat heater 

The heating level can be changed during the following operating conditions by pressing the heated seat switch:

The change is from level 2 to level 1 or from level 1 to level 2 via seat heater "Off"

Changing the heating level during heat-up mode 

If the heated seat switch is pressed during heat-up mode the heated cushion is actuated by the heated seats control unit with the maximum heat output for the selected heating level. After the expiration of the heat-up period that was calculated before the heating level was changed, further actuation takes place in continuous heating mode using the selected heating level.

IMPORTANT The timer control is not interrupted when the heating level is changed.

Changing the heating stage during continuous heating mode 

Switching off manually 

Press heated seat switch repeatedly until the integrated light-emitting diodes go out.

IMPORTANT After circuit 15 off the seat heater is switched off and the status when it was switched off is not saved.

  Seat heater (SIH) location of components   GF91.30-P-0003-02MCU 
REFER TO SYSTEM WIRING DIAGRAMS Wiring diagram of seat heater (SIH)   PE91.30-P-2000MCU 
  Seat heater control unit, component description N25/5 GF91.30-P-5214MCC 
  Cockpit switch group, component description S6/1 GF54.25-P-4300MCU