Had my d3 intstalled profesionally but It dont dim at night and I dont think the vss is hooked up. I had two wire left in the box thats why I am thinking this. how can I tell and does the 2005 f250 have a vss> Is it worth the trouble to hook up?

yes that truck has a vss wire, and most have it in the radio harness, it is grey/black. the dimmer lead should be connected to the brown wire at the light switch (just across the dash). if you had two lengths of wire left over, i'm guess there was a pink (vss) and a purple/white (reverse). the pink lead should have been used and hooked up, the purple/white is usually used for back up camara but does not hurt to have it connected.

if you had the unit done by a shop, i would suggest going back and insisting they connect the speed pulse wire (vss) because it allows the avic unit to be more accurate. i would also have them hook up the dimmer lead so you don't have a spotlight in your eyes at night. these two connections, in my eyes, are a standard connection for ANY in dash nav unit, d3 included, and should never be omited.