Wired up a relay box last night, finished everything today. I had done this in my XJ and really liked the idea and neatness with it. I had read about the idea on NAXJA from a member named FitchVA, and he named it his "fitchbox" So I give him all the credit for this idea.
First off, the only lights I have on my Jeep currently are my two bumper lights. I plan on adding two windshield mounted lights, and two more on the rear bumper. With this box, I am able to mount a fuse block and three 30A relays in it, and pre-wire everything.
Started with a project box from Radio Shack, cost about $6 or so. Drilled two holes, one for my 4GA power and one for my switches/accessories:
Went and mounted the fuse block and three relays. I jumped a ground for all three, and a tail coming out of the box to ground to my tub, for the relays. Then I went ahead and jumped my power for all three. I used a piece of 16/4 (16 gauge, 4 conductor) wire I had laying around. The red is used as a power for the switches and the black, green, and white are my signal wires going between my three switches and relays. So those three went on the ACC terminal of each switch, and the red was jumped between the three switches and went back to my fuse block. This is nice because all of the wires are in cased in a single run, and the switches, even though it is just an LED on them, are fused.
Mounted the three switches in the three blank spots I had on my center bezel. There is a bunch of plastic behind them, so I just took a needle nose and broke it all out to fit the switches. grounded them right to the tub, behind my center console. Wire tied the 16/4 under the dash and ran it into the engine compartment with the main harness.
Under the clutch fluid filler, is a nice area where I had mounted my relay box. I can't say every TJ will have this spot because it looks like something should be there. But you can mount the box anywhere.
Ran a piece of 4GA copper from the main fuse block to my relay box, crimped both ends and terminated. I had this laying around, so I used it, even though it may be over kill.
So now that everything is all mounted up and wired, it makes things alot easier when I go to install my other lights. It's as simple as grounding the lights and running a single wire to the relay that corresponds with the switch in the cab (empty terminal on the remaining two relays).
Wired up the lights on the bumper, wire-loomed and flipped them on.