[EdT]

The light sensor in the SID controls the brightness of the SID display and the odometer only. The rest of your cluster illumination is totally controlled by the panel illumination knob down below the switches for headlight, fog light, etc.

When the car is first started, the SID and odometer are on full bright no matter what. Then, in a few seconds, the SID will dim if it's dark, to the level set by the rest of the cluster illumination (speedometer, tachometer, etc.)

What do you see at night? Is it only the SID that is dark, or everything else? Is the speedometer lit or dark? Do the gauge needles move? What happens when you move the dimmer wheel?

 

[EdT]

Are the gauge lights totally, completely off? At minimum brightness they can only be seen in full darkness. Also, your temp and tach gauges work okay? What happens when you press Black Panel?

What happens when you shine a bright light right into the sensor?

I am puzzled by what is happening, specifically that the dimmer setting does nothing when the SID is installed. Even in full daylight, on the NG900 the dimmer wheel varies the brighness of the gauges, and the illumination never goes out. And in full darkness, the SID and odometer illumination first is full brightness, then goes to the level set by the dimmer.

In other words, I don't see that a simply malfunctioning SID light detector would cause these problems.