Wiring truck cap 3rd brake light

[Basilius]

I have a 1998 Ford Ranger XLT 2.5L 4x2 and a Glasstite cap, and I'd like to wire the third brake light with quick release connectors. The cap has an interior dome light and four wires in total coming out of it (red, red, red/black, black), with two wires going to the dome light (red, black) and two wires going to the 3rd brake light (red, black). My truck has separate brake (red), reverse (white), and blinker (amber) lights and I bought a wiring kit with quick connectors, so I'm hoping the job won't be too difficult. I don't have any experience doing car electrical work, however I do know how to splice and solder wires, and I have heat shrink to protect the wires. I also bought a quick connect wiring kit (American Technologies C90-907) and have other connectors that might work (computer power supply extensions with male/female connectors).

What would be the best way to wire the truck cap third brake light? I attached some pictures and can take more if necessary. Thanks in advance

 

[4x4junkie]

Welcome to TRS.

I'm thinking it would be easy enough to simply remove the center high mount stop lamp (CHMSL) above your truck's back window and tap into the wiring behind there, then run the wires over to the side and down under the bed rail or to wherever they need to go.
You didn't make clear whether you also wanted to hook up the cap's dome light... If so, then you'll have the wire for the cargo light (if your truck has one) right there also which you can tap onto and run that out to your cap's dome light.

If the dome light part isn't important, it's only a matter of finding the brake circuit wire at the rear of the truck and tapping onto that (since your blinkers are separate there's no worry about needing any converters or adapters for it).

On my '94 the brake lamp circuit has a light green wire. I don't have '98 diagrams so unfortunately I can't confirm if '98 is the same color or not.

Hope that helps