I have a Glasstite cap for my Ranger and it has four wires (black, white, yellow, green), and no interior dome light. My truck also has a four wire trailer connector (brown, white, yellow, green) near the bumper. What would be the best way to wire the 3rd brake light on the cap, and is it possible to wire the cap using the trailer connector? I've never done electrical car work before. thanks

 

Does your cap have a harness end on it like the 4 way flat plug for your trailer connector? Mine has one, but it's only 3 wires, so that's what I'm going to plug into and then wire it in behind the tail light.

You can probably google, or better yet, call the manufacturer directly and ask what each color wire will do, or look at each source of power.

Obviously one will be ground, one is power for your overhead light probably... the other one is gonna be for a 3rd brake light.. not sure what the fourth would be.

Buy some wire taps and tap into your wiring behind the tail light. Not sure if your brake light wire on the tail light also is the same wire that works your turn signal.. if so then you might need to run a dedicated brake light wire from your truck's 3rd brake light wire (can tap into it on cab floor under driver's side seat), that way you don't have your cap's 3rd brake light flashing when you use your turn signal.

 

No, the four wires coming from the cap are bare (no connector), and there's no interior overhead light in the cap. The truck brake light and turn signals are separate (amber brake light). I'll see about contacting the manufacturer, but I don't think they exist anymore. Is it possible to use the trailer wiring connector to connect the cap brake light, since that would be much easier?

 

Is it possible, yes. But just because the wire colors are the same doesn't always mean they do the same thing. When I did mine, I ditched the light that came with it and made my own with 3 lights on each side. They work independently as turn signals and together as a brake light. Works much better than factory and I have gotten a lot of compliments because of it.

 

If you know which wire on your trailer harness controls the brake lights, then yes, you could tap into it.. just as easy to tap into your brake light wire behind the tail light housing, and it's going to be a lot more obvious which one is your brake light wire that way.