OVERVIEW
The 1999 Model Year E38 and E39 vehicles are equipped with a new Center Console Switch Center (SZM).
The SZM directly controls
- Front Seat Heating
- Rear Window Roller Blind
The SZM provides a diagnostic interface with the DIS/MoDiC via the K BUS for the seat heating and Rear Roller Blind systems.
Identifying Center Console Switch Center (SZM). Scheme 239
SZM also provides a unitized switching center for Park Distance Control (PDC), Dynamic Stability Control (DSC III) and Electronic Damper Control (EDC).
The switch signal output for these systems is a direct output signal. All diagnosis functions are carried out through their respective control systems.
SEAT HEATING OPERATION
The front seat heaters are adjustable through three ranges of heating output temperature.
Pressing the respective seat heater button once provides stage 1. All three LEDs illuminate and the heating elements are provided regulated output current producing a seat temperature of 111°F.
Pressing the button a second time provides stage 2. The top LED switches off and the heating elements are regulated to an output temperature of 102°F. Pressing the button a third time provides stage 3. The top and middle LEDs are off and the heating elements are regulated to an output temperature of 95°F.
The SZM monitors the seat heating element temperature via an NTC feedback signal to regulate the output current which maintains the seat temperature.
Seat heating is switched off by pressing the button a fourth time, pressing and holding the button for more than 1 second or when the ignition is switched off.
REAR WINDOW ROLLER SUNBLIND OPERATION
The roller sunblind is activated by momentarily pressing and releasing (one touch) the sunblind rocker switch in the SZM. The SZM activates the motor in the appropriate direction. The SZM switches the motor off when the motor amperage increases indicating the blind has reached the end of its intended travel.