I have a 2003 Denali with auto headlights. I'm thinking this is affecting the nav screen. Its always on day and even if i manually switch the lights on nothing happens. Do i need a special part?

you need to hook up the illumination wire(orange) once that is connected and you turn your lights on the unit will dim

When this wire is connected and you select DAY or DAY/NIGHT the dimmer should be turned of right?

Installer hooked up the right wires. Still nothing though

This is like the same thread http://avic411.com/forum/viewtopic.php?t=8620

for the second time today

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i think for the right polarity on that truck u gotta go to the bcm.

if you pull the under dash off you can see like 5 plugs facing the drivers seat.

the wire you want is on the far right plug that only has like 5 wires in it

grey/black= illumination

the radio plug has an illumination but its not the right polarity so use this