so my screen is very bright on my D3 until i turn on my lights.....i have messed with the settings and have the brightness all of the way up... any suggestions? i do not think it matters but my headlights are HID's

It is supposed to dim when you turn on the headlights. Because you don't need the screen to be as bright at night time as you do during the day time.

But anyway, you can change the settings for the screen (brightness, contrast, and dimming) for both modes, day and night. While in nav. mode, hit MENU > SYSTEM > V.AJUST

Brightness and contrast are adjustable between +24 and -24, +24 being the brightest.

Dimmer is adjustable between +1 and +48, +48 being the brightest.

Turn your headlights off, and adjust the settings to what you want for daytime driving. Turn on your headlights, and adjust the screen for how you would like it for night driving.

It's all in your manual on page 127 if you'd care to take a look.

do daytime running lights affect the brightness at all? i've noticed that mine doesn't switch at all.

I don't know, I guess that would depend on the type of car and how they have it set up. IIRC there's a topic or two dealing with a workaround for that.

EDIT: http://www.avic411.com/forum/viewtopic.php?t=9466

Only takes a couple of seconds to do a search

I would think that Day running light would effect the dimming function of the unit as the ILL (orange) wire on the harness only needs to see the 12VDC power to it in order to dim the unit. If your lights are on at all times, Maybe the installer didn't hook up that wire and if so then the unit stays bright at all times.