BMW 7 Series: Front Seat Heating

The seat heating is standard as part of the comfort seats. The seat module is functionally responsible for seat heating.

The seat heating can only be activated from terminal 15 ON. The status of terminal 15 ON is issued by the Car Access System 4 via the K-CAN2. The junction box electronics thus know the status of terminal 15.

The central gateway module transfers the signal to the K-CAN. The seat module is connected to the K-CAN and receives the status of terminal 15.

The button for the seat heating is located in the IHKA/audio control panel. The control panel is connected to the control unit of the integrated automatic heating and air conditioning system.

Pressing the seat heating button, selects the heating stage as shown in the following list.

SEAT HEATING BUTTON

3 - High
2 - Medium
1 - Low
0 - Off

If the button is pressed for longer than 1.2 seconds with the seat heating activated, the seat heating will be switched off.

If, after terminal 15 OFF, the junction box electronics receive the status terminal 15 ON within 15 minutes, then the last selected function that was activated will come into operation.

The indicator for the selected heating stage is controlled by the seat module. The signal must be sent via several bus systems.

The seat heating module is connected to terminal 30B for the seat-heating load current.

Fig. 100: Identifying IHKA/Audio Control Panel With Buttons For F01/F02 Seat Heating

COMPONENTS DESCRIPTION CHART

1. Seat-heating button, driver's seat
2. Seat-heating button, front passenger's seat

Seat Heating with Seat Module

When the vehicle wakes up, the junction box electronics determine whether a seat module is installed in the vehicle. It sends a corresponding query via the K-CAN2 for this purpose. The central gateway module transfers the signal to the K-CAN. This allows the seat module to receive the request, respond to it via the K-CAN and take control of the seat heating function.

The seat module has sole responsibility for the seat heating function. The integrated automatic heating and air conditioning system evaluates the button status and sends the button status via the K-CAN to the seat module.

The seat module evaluates the requests for the desired heating stage, as well as controls and monitors the seat heating functions. The seat-heating pads are connected to the seat module. A NTC resistor in the seat-heating pad is monitored to control the temperature.

Depending on the heating stage, the seat module sends the request for the function to be indicated in the button LEDs to the integrated automatic heating and air conditioning system.

The seat module is connected to terminal 30B for the seat-heating load current.

A fault in the seat-heating system results in a corresponding entry in the fault memory of the driver's seat module.

Power reduction of seat heating

The energy management system in the vehicle can activate the seat heating at a reduced power level corresponding to the vehicle's energy balance. The energy management is located in the digital engine-control system.

The digital engine control sends the request to reduce power via the PT-CAN. The central gateway transfers the information to the KCAN. This allows the seat module to receive the request to reduce power.

The reduction stages are:

• Operation of seat heating in Stage 2
• Operation of seat heating in Stage 2 at only 50%
• Seat heating OFF.

NOTE: In the event of a power reduction, the LEDs in the seat-heating buttons are not switched off.

During a starting cycle (terminal 50 ON) or when the seat adjustment switch is operated, the seat module prevents the seat heating from functioning. The LED indicator for the activated seat heating remains lit.

Heating Circuit for the Seat Heating

The F01/F02 seats are equipped with a two-circuit seat heating system.

Two-circuit seat heating system

A seat-heating pad is located in the surface of the backrest. Two seat-heating pads are integrated into the seat surface. Both seat-heating pads are supplied with power by the seat module.

There is a NTC resistor in each seat-heating pad in the backrest and seat surfaces. This serves as a temperature control.

Fig. 101: Schematic Diagram Of Two-Circuit Seat Heating System

COMPONENTS DESCRIPTION CHART

1. NTC resistor in the backrest-surface seat heating pad
2. NTC resistor in the seat-surface seat heating pad

The customer can adjust the seat heating air stratification individually. Select the menu item "Settings" using the controller in the Central Information Display.

Settings

• Air conditioning
  • Seat heating distribution
    • Driver
      • Front passenger

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