Instrument and display lighting: Notes

WARNING: This page is about a different car, the 2006 Saab 9-5. However, it is still accessible from the selected car via links, so may be relevant.

So that the main instrument unit gauges, lamps and information display will be easy to read in both daylight and at night, as well as to achieve optimum bulb life, the main instrument unit's control module regulates the lighting intensity of the display according to the brightness in the cabin and the rheostat setting selected by the driver.

The rheostat is connected to the SID control module and the cabin light sensor is mounted in the main instrument unit. The main instrument unit reads the light sensor value and transmits this on the I-bus. The SID control module processes this value together with the rheostat value and continuously sends information about the following lighting values on the bus:

Fig 1: Instrument And Display Lighting With Communication Diagram

Courtesy of SAAB-SCANIA OF AMERICA, INC.

Fig 2: Instrument And Lighting - Circuit Diagram

Courtesy of SAAB-SCANIA OF AMERICA, INC.

Rheostat value, unit %.
Rheostat value Night Panel (this value is not used by the main instrument unit).
Light intensity in the cabin, unit Lux.
Display lighting, unit %.