I picked up some white LEDs today to do the LED dome light mod, and im pretty much done it, but theres a problem. I took the original bulb assembly apart and stripped it all down to the wires. There is a green one, which is the power, and a black (or something very dark) which im assuming is the ground. I wired up the power leads from the LEDs to the factory power wire and the LED's ground wire to the factory ground wire but nothing happens. They turn on if i attach the LED ground wire to the bare body metal, but if i do that, they wont turn off. Does anyone know whats going on here?

 

sounds like a body mount ground. when you unscrewed your domelight from the ceiling, you probably took out 3 screws. one connected to the power wire within the domelight housing, one connected to the ground wire in the domelight housing, and the third screw grounds to the bare body metal in the threads that catch it. if you make only one or two connections, you'll see your dome light doing some goofy stuff. make that third connection, and youre golden.

 

Your truck came with either a dome/map light or dome only light.

The green/orange is hot with the ignition on and hot for a few minutes after it's off. If you have power locks, it also may go hot for a while after the doors are unlocked. This wire is for the map lights and if your modded lamp doesn't have map lights, it will not be used.

The other hot wire is black/blue. It operates almost the same as the green/orange EXCEPT it will also be turned off when both door ajar switches show the doors as closed and it will wake up for a while when either of the doors are opened. The black/blue is for the dome light.

If you try to use the black/blue as ground for the green/orange or vice versa, nothing will happen. As Kris said, the ground path for most Ford dome lights is through one of the mounting screws. You need to arrange the wiring for your LED to use that ground.

So, if you are doing dome light only, the short answer is black/blue for hot and chassis for ground.

 

im trying to hook up a dome light from autozone. I have a 2000 ranger I have the black/blue wire and green/orange wire my green wire is alway hot the black/blue wire is not hot at all I have my dome light mounted and its grounded but I can't seem to make that black/blue wire do anything. I assumed it was to be turned on when the door was opened. but even with open doors it does nothing.