OK so I finally went down to a junkyard and harvested an entire tail light socket assembly, two actually, from an unfortunate junked 1988 XJ. They all looked complete, ground wires still attached and all, with the only wildcard being that a trailer wiring bundle was spliced onto the original wires in a few places. All that was removed and I replaced my hacked up socket assemblies with these new ones. I swapped on all my old bulbs, removed the panels and plugged it all in, etc.

Now here's what I have: both brake lights turn on as "running lights" like they're supposed to when the headlights are on and do NOT light up when I press the brake pedal. BEFORE I did the swap, the brake light on the left (which was not hacked out) at least lit up but now neither do when I press the brakes. I even put another set of brand new bulbs in just in case.

I electrical taped the gaps in the wiring insulation where the trailer wiring had been attached and on one wire there's still this metal THING spliced on (somewhere to attach a ground wire?) that I have not removed. Is any of this my problem? Why won't either of my brake lights light up?

 

Stop lamps are the light blue w/tracer wire. One end to the bulbs, other end to the brake pedal switch. There's a lot of extraneous wiring back there for trailer lights that can foul things up.
Perhaps this will help:

 

Thing is, all I swapped out was from the plug sitting near the back wheel wells to the lamps themselves. I was getting a brake light before the swap but not after.

 

Well, took off that metal splice bit that was still attached to one side thinking maybe it was causing a short and no dice. I am missing something simple with these but I don't know what it is.

So to refresh: There's no trailer wiring bundle on this anymore and the socket assembly I switched out worked, with the exception of the brake light that was hacked off by the OO. Brake lights light up when the headlights are on but not when stopping on either side now. Ideas?

 

The brake light and running light are separate filaments inside the same bulb. The running lights are powered by a blue wire. The brake lights are a light blue/tracer wire. Both share a common ground.
Do you have +12V on the light blue/tracer wire when the brakes are applied?

 

I probably need to borrow a voltmeter to see if I am, at this point I think I have no choice.

 

So Here's the wiring diagram from my Haynes Manual:



So I have power, according to my friend's test light, all the way to the socket assemblies so by all rights, I should have brake lights. We found the fuse had been burned out so it is possible the "bad" socket assembly I got burned something out. He also verified there's power coming to the pedal switch but he was not able to eyeball where the pink wire up there went, and I had forgotten to bring this book with me at the time.

My question is, that headlamp switch that the pink wire goes to from the fuse panel, and that the blue wire going to the brake light socket itself comes from? Where the hell is it? Damned if I could figure out where it is under there. My working theory here is that thing was either tripped or shorted out by whatever burned up the fuse.