Seat heater, function - GF91.30-P-0003G

MODEL 463.306/336/346 with CODE (H10) Driver and front passenger heated seats with CODE (H11) Rear bench seat heater as of model year 2011/YoM 10 

MODEL 463.202/222/237/270/271/303/340/341 with CODE (H10) Driver and front passenger heated seats with CODE (H11) Rear bench seat heater as of model year 2009/YoM 08 

MODEL 463.236 with CODE (H10) Driver and front passenger heated seats with CODE (H11) Rear bench seat heater except CODE (ZS6) Special protection version FB6 except CODE (ZS7) Special protection version FB7 as of model year 2009/YoM 08 

MODEL 463.236 with CODE (ZS6) Special protection version FB6 with CODE (ZS7) Special protection version FB7 as of 

Model 2009/modification year 08 MODEL 463.247/248/249/254/270/271/303/340/341 up to 31.8.08 with CODE (H10) Driver and front passenger heated seats with CODE (H11) Rear bench seat heater as of model year 2007/YoM 08 

Function requirements, general 

• Circuit 15R ON or circuit 15 ON

The status of circuit 15 is transmitted by the EZS control unit via interior CAN.

Seat heater (SIH), general 

Using the SIH, it is possible to heat the seat cushions and the backrests of the front seats in three heating stages. In vehicles with code (H11) Rear bench seat heater or in model 463.236 with code (ZS6) Special protection version FB6 or code (ZS7) Special protection version FB7), the seat cushions and the backrests of the rear seats can additionally be heated in two heating stages.

The SIH comprises the following subfunctions:

• Function sequence for manual front SIH switch on/off 
• Function sequence for automatic front SIH switch off 
• Function sequence for manual rear SIH switch on/off 
• Function sequence for automatic rear SIH switch off 
• Function sequence for automatic SIH switch-off 

Function sequence for manual front SIH switch on/off 

The operation of the front SIH takes place via the left front SIH switch and the right front SIH switch in the upper control panel control unit. The signal of the left front SIH switch and the right front SIH switch is read in directly by the upper control panel control unit.

Depending on the request, the upper control panel control unit discretely actuates the following heating elements:

• Left front seat heated cushion
• Left front backrest heated cushion
• Right front seat heated cushion
• Right front backrest heated cushion

The heat output depends on the number of the times the relevant front SIH switch is pressed:

Press once: Heating stage 3 (100 % heat output)

Press two times: Heating stage 2 (70 % heat output)

Press three times: Heating stage 1 (40 % heat output) Press four times: Seat heater is switched off

The particular heating stage that is active is indicated via red LEDs in the corresponding front seat heater switch.

Function sequence for automatic front SIH switch off 

The timer control of the front SIH is implemented by the upper control panel control unit. The timer control of the front SIH following the operation of a front SIH switch is defined as follows:

• Heating stage 3 is active for t = 5 min The system then automatically switches over to heating stage 2.
• Heating stage 2 is active for t = 10 min The system then automatically switches over to heating stage 1.
• Heating stage 1 is active for t = 20 min The system then automatically switches the seat heater off.

Function sequence for manual rear SIH switch on/off 

The rear SIH is operated via the left rear SIH switch and right rear SIH switch, both of which are located in the B-pillars. The rear SIH switches are read in by the rear SIH control unit.

Depending on the request, the rear seat heater (SIH) control unit discretely actuates the following heating elements:

• Left rear seat heated cushion
• Left rear backrest heated cushion
• Right rear seat heated cushion
• Right rear backrest heated cushion

The heat output of the rear SIH depends on the actuation of the corresponding rear SIH switch:

Function sequence for automatic rear SIH switch off 

• Heat stage 1

  Press one time: Heating stage 1 (33% heat output)

  Press again: Heating stage 1 Off

• Heating stage 2

  Press one time: Heating stage 2 (100% heat output)

  Press again: Heating stage 2 Off

The particular heating stage that is active is indicated by a red LED in the corresponding rear seat heater switch.

The timer control of the rear seat heater is implemented by the rear seat heater (SIH) control unit. The following timer control of the rear seat heater is stored after actuating the left rear seat heater switch or the right rear seat heater switch:

• Heating stage 2 is active for t = 5 min

  The system then automatically switches over to heating stage 1.

• Heating stage 1 is active for t = 30 min

  The system then automatically switches the seat heater off.

Function sequence for automatic shutoff of the SIH 

When one of the following criteria is met, the SIH is switched off; they are:

• Switching off in the event of component defect
• Switching off in the event of component overtemperature
• Exceeding the interior temperature (front SIH)
• Switching off after circuit 15R OFF
• Switching off the front SIH in the event of undervoltage
• Switching off the rear SIH in the event of undervoltage
• Switching off in the event of overvoltage
• Switching off during starting procedure

The criteria are listed in the order of decreasing priority; i.e. if the SIH is switched off due to a criterion with a low priority and then another switch-off criterion with a higher priority occurs, this is treated as described for the criterion with the higher priority.

• Switching off in the event of component defect:

  To prevent the SIH from being able to be activated if a plug has become disconnected or a line has been sheared off, the resistance value present is checked with a cycle of t = 10 ms at the output. If the resistance value is above

  R = 2 kΩ, the operating switches are no longer queried. However, the measurement can only be carried out when the SIH is switched off. If the SIH is disconnected while it is switched on, this will not have any influence on the heating process. As long as one of the two heating stages is active, the switch query is still functioning. The respective SIH switch is not deactivated until the SIH of the particular side is switched off.

• Switching off in the event of component overtemperature:

  To prevent the electric components from overheating, their temperature is monitored. In the event of impending overheating, the SIH is switched off.

• Exceeding the interior temperature (front SIH):

  If the interior temperature (or the outside temperature if the interior temperature is not measured) is higher than the defined switch-off threshold, certain heating stages or the complete SIH cannot be switched on.

  • Heating stage 3 can no longer be activated if the interior temperature is T ≥42 °C. Heating stage 2 is switched on automatically.
  • Heating stage 2 can no longer be activated if the interior temperature is T ≥45 °C. Heating stage 1 is switched on automatically.
  • The SIH can no longer be activated if the interior temperature is T ≥55 °C.
• Switching off following circuit 15R Off:

  After switching off circuit 15R, the SIH is switched off as well (load output and function indicator). However, the internal timer control continues running for t = 5 minutes, while circuit 15C is ON. If circuit 15R or circuit 15 is switched on again, the SIH continues running as part of its programmed timer control.

• Shutoff of front SIH in the event of undervoltage:

  The voltage value (battery voltage) is transmitted by the EZS control unit via interior CAN and received by the upper control panel control unit. After switching on the SIH, the SIH is switched off for t = 4 min, when the values are falling below the undervoltage threshold of U ≤9.8 V for t ≥ 5 s. However, the timer control continues to run. Switching on again is only possible when a permissible voltage of U ≥ 10.6 V is present for t ≥5 s. After another t = 4 min, the switch-off threshold is raised to U = 10.8 V and the switch-on threshold is raised to U = 11.6 V. If an undervoltage shutoff is detected, the light-emitting diodes that are active in each case of the corresponding SIH switch are flashing with approx. f = 1.5 Hz and a brightness of 50%. The flashing frequency of the light-emitting diodes on both sides (left/right) occurs synchronously.

• Shutoff of the rear SIH in the event of undervoltage:

  The voltage value (battery voltage) is measured by the rear seat heater (SIH) control unit from the internal circuit 30. When values are falling below the undervoltage threshold of

  U ≤ 10.8 V for t ≥5 s, the rear SIH is switched off. Switching on again is only possible after a permissible voltage of U ≥5 V is present for t ≥ 11.6 s.

• Switching off during the starting procedure:

  During the starting procedure, the SIH (load only) is switched off. The timer control continues to run during the starting procedure. After the starting procedure has occurred, the SIH is switched on again with a delay of t = 2 s. The original status of the function illumination remains unchanged.

• Switching off in the event of overvoltage:

  When the overvoltage threshold is exceeded, the SIH (load only) is switched off. However, the timer control continues to run. The light-emitting diodes of the SIH switches go out. It is not possible to switch them on again until a permissible voltage is present again.

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	Seat heater (SIH), block diagram		GF91.30-P-0003-03G
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