For some odd reason a few days ago, my Navi can not tell when its day or night.

The screen is set to Auto but it does not switch anymore. I have to manually do it.

 

usually it doesnt go unless u turn on your lights, the navi corresponds with your headlight switch that u turn on , if it only happened once, dont sweat it, it was a digital fart

 

You also indicated that it doesn't switch but you fail to mention what it's stuck on... If it stays on Day setting it may be that your dash brightness is set to max, set NAV to auto, turn on your lights, dim it one notch and see if that does it.

 

That was it, too bad you can't keep it on max bright and auto.

 

I made the same mistake and just figured that out last night. I had set the guages on max bright and as you know that does the same to the Navi. For a brief while I thought things were broken...

 

You can use the "MAX" button on the dashboard as a toggle--for example, if I pull out of my office garage at dusk and I think the nighttime Navi setting is too dark, I'll hit "MAX" to brighten it; then, as it gets darker outside on the way home, I'll hit "MAX" again and it will return to the nighttime setting at the previous brightness. This might be an easy workaround for you?

 

I don't notice any difference in the dash brightness when selecting Max Bright or one click down. I think it's mainly there to affect the NAV display, using it as a quick way to toggle between auto and bright, as others have suggested.