SaabCentral Forums banner

interior light sensor?

7K views 12 replies 8 participants last post by  idontknow 
#1 ·
I was just wondering if our cars have a light sensor that changes the back-lighting of the instruments and screens depending on how light out it is. I've noticed that in dim-light that the nav and SID screens will dim occasionally and then return to full brightness, and was wondering if it was because of a sensor of this type. Thanks SC!
 
#3 ·
At night turn on your interior lights and watch the display brighten then dim when you turn off the interior lights.
 
#4 ·
so its that black half-circle that the alarm light is around on the windshield side of the SID? I couldnt find it in the haynes manual, and i just want to make sure that the lights dimming and brightening is normal. I noticed it dimming and brightening intermittently when i was driving around dusk with the lights on.

EDIT: didnt see the pic the first time. thanks a lot!
 
#8 ·
Although that is the solar sensor pictured on top of the dash, I believe it's function is to provide feedback to the ACC. The light sensor for the display lighting is on the face of the radio. If you look at the Select knob on the face of the radio, you'll see a small circle maybe 1/8" in diameter at approx. the 11 o'clock position relative to the select switch. Try shining a flashlight at that spot and you'll see what I mean. Note that only the led display screens are adjusted; not the actual i/p backlighting.
 
#9 · (Edited)
WIS says:
Instrument lighting:

ICM controls the instrument and button illumination with the help of:

• Brightness control buttons (rheostat function) on SIDC.

• Light sensor on rear of SID that measures the ambient light from the front.


ICM uses these values when calculating a suitable brightness for the instrument and button illumination. ICM transmits the bus message "Instrument illumination, rheostat value" with a value between 0-100% on the I-bus.

The brightness control comprises a +/- switch that provides ICM with information on the driver's choice of instrument illumination. SIDC transmits the current button press to ICM, which increases or decreases the rheostat value accordingly.

A PWM signal from SIDC on pin 4 to ICM pin 14 indicates the button (+/-) that has been pressed. This signal is a 5V 960Hz square wave with pulse ratio 40% for the up button (+) and 60% for the down button (-). See the SID control panel table.

The light sensor that measures brightness from the front is fitted to the back of SID together with the alarm LED.
The light sensors have a measuring range between 0 and 40000 Lux.

I'll test it tommorow by covering the solar sensor :)
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top