I did not install this unit and I'm pretty sure that the illumination wire is not connected based on my searches here. I have an 03 Tahoe. One of my questions is simply, should I notice a brightness difference when manually switching from daytime to nighttime? I'm not seeing any change when I do this. I have not tried adjusting the brightness of each mode either assuming they may be set identical by default. Is there an explanation in the User Manual of how to adjust? I don't remember seeing it. Also is there any way to dim with the dash dimmer functionality?

 

I'm going to be cracking my dash open tonight to find a connection.

The daytime/nighttime button only changes how the unit reacts when your lights are on. Obviously, if your ill wire isn't connected, it assumes your lights are off at all times, and will continue to give you full brightness/daytime mode.

 

IIRC, If you choose the "daytime" setting once your wire is connected, you can keep the bright daytime display at all times.

 

Regarding the brightness, you can adjust the brightness of the dimmer function, but it affects all screens at night. I.e. If you want it to dim the map display, it will also dim the AV screens. I find that the unit is too bright at night, but if you need your lights on during the day (i.e. rain), the screen can be too dim when it's still bright out.