Here's another nice reference from [MENTION=20116]darkie3495[/MENTION] that I used to help in my wiring:
And another link I used alot:
Wiring Aftermarket Lights with Toyota FJ Cruiser Off Road Aux Switch - Toyota FJ Cruiser Forum
Here's what I did, it works, others may or may not agree with all of my moves, but I'm confident I won't have any electrical fires, my lights work, the dimmer works right, and I'll be able to troubleshoot the wiring if something fails, which is all that matters to me:
Cut the connector and ring terminal off of the wires on the end that does NOT plug into the FJ switch. These wires need to be wired to other things. You can cut them at the connector, or up closer to the FJ connector, whichever you prefer to your liking for cleanliness. (I like lots of extra wire in case I screw up, or need it in the future, so I cut in about the middle of the harness)
Take that red wire w/ blueish purple tracer (line) on the new harness (pin 1) and run it to one of the coil prongs for the relay you should be installing (typically labeled 86). Now take the red wire w/ green tracer (pin 4), and tap it into that same wire using one of these:
Now take the black wire (pins 2) and tap it into the ground on the DAC switch, which is a white and black wire.
Now take the brown or grey wire (the one next to the purple wire, pin 5) on the new harness, and tap that into the white wire the green tracer on the DAC switch. Notice, there are TWO OF THESE. I tapped into the one that was next to the green wire on the DAC switch, NOT the one right next to the white/black one you just tapped into above.
Now take the green wire with a redish purple tracer (pin 3) from the new harness, and send that to one of these:
or these
that you should be using on the 'lower right section 7.5A fuse' as mentioned in the above wiring diagram from [MENTION=20116]darkie3495[/MENTION].
Now take the last wire, should be the purple one (pin 6) and tap it into the green wire on the DAC switch. (this green wire should be right next to the white/green wire you tapped into previously).
This takes care of the FJ aux switch. You should be able to turn the key to ACC now and test that the switch lights up and dims the same as everything else in the car, and the little light should come on when you press it.
Now we go for the relay.
here's a diagram that may help, mind you the colors, amp ratings, etc. mean nothing, it's just for your reference of wires and where they are going:
You should have one wire on it already, it should be on one side of the coil, typically labeled 86. Now wire a ground to the other side of that coil, usually prong 85 (note that these prongs are not always exactly opposite each other. go by the numbers).
Now you're relay should click when you push the new FJ button (assuming the car is on). All that's left is the light.
Wire 12 volt source (Such as your + side of new fuse block, or + terminal on battery) to terminal 30 or 87 on the relay. Then wire the other terminal (87 or 30) to the + connector on your light. MAKE SURE YOU HAVE A PROPERLY SIZED FUSE BETWEEN THE + SOURCE AND THE LIGHT (whether it's between the source and the relay, or the relay and the light, just make sure its SOMEWHERE on that line). You can use one of these to get a fuse in there if you don't have a fuse block:
Then run the (-) connector on your light to ground. This can be the (-) terminal on the battery or typically a metal bolt/nut on the body.
Note: your relay may have 5 pins, in which case the 5th one should be left open and is probably labeled 87a.
2nd Note: I wired just slightly different from that reference I have above from darkie. Instead of wiring both pins 2 and 5 to ground, I wired 2 to ground and 5 to the DAC green/white wire. When I did both to ground I had no dimming capabilities on the button. That green/white wire on the DAC button (the one next to the green wire on the button) goes through a dimmer then to ground, and that's how I got my FJ buttons to dim properly.
3rd Note: Use proper wiring sizes.
I realize this is long, probably vague, and I haven't really revised it. Just tried to get something out fast to help you. If you have any questions, PM me and I can do what I can to sort you out.
Good luck!