Instrument and Display Lighting

The instrument lighting and the displays on the Saab Information Display (SID) unit and ACC are controlled by means of the rheostat when driving at night.

When driving in the daytime, the brightness of the display is regulated by means of a light sensor in the SID unit.

Light intensity in the cabin
The SID unit uses the light intensity as a basis for calculating the brightness of the display lighting. "Light intensity in the cabin" is measured by the light sensor in the SID unit and the reading obtained is also made available to other systems via pins 16 and 17.






Rheostat
The rheostat output is a PWM voltage which controls the clock and push-button lighting in the SID unit. It is also used for calculating the brightness of the display lighting.

The SID receives the rheostat signal on pin 22 and makes it available to other systems via pins 16 and 17.





Display lighting
Display lighting brightness is calculated on the basis of the rheostat output and the "light intensity in the cabin" reading.

The display lighting brightness reading controls the SID unit's own display.

The SID makes the display lighting brightness reading available to other systems via pins 16 and 17.