I'm re-posting this from the other thread:
http://www.chevyequinoxforum.com/f4/2018-questions-1850/index2.html#post14364
BTW, ONE IMPORTANT PIECE OF INFORMATION:
THE DIMMER SWITCH IS A SPRING-LOADED PUSH-BUTTON.
It needs to be (gently) pushed in and it then pops out a little so it can be turned to adjust the lighting.
When done adjusting the IP (instrument panel) lights, either leave the button in the "out" position or push it back in to "lock" the setting in place.
This is what I posted on another thread:
http://www.chevyequinoxforum.com/f4/2018-questions-1850/#post14053
The dimmer knob to the left of the steering wheel on the lower dash has very little effect on the overall radio display, from what I've perceived by playing around with everything.
From memory, you'll need to select "Settings" on the touch screen Home Page, then select the sub-menu for either "Display" or "Vehicle". That contains a setting which will alter the display lighting. When you find the "Display" menu, select "Auto" so that the MyLink system will automatically adjust the lighting to what is best given the conditions it perceives.
When going into the "Settings" menu via the NAV display, for some settings and adjustments the engine may need to be running (or push start/stop ignition button to turn the accessories on - don't remember which).
Please keep us posted on whether you're able to solve this issue or need further assistance.
If that still doesn't adjust the lighting on the IP, then I'd suggest a trip to the dealer.