So I actually installed this on Saturday the 12th before reading your most recent replies.
I had already ordered a relay off of Amazon for a few bucks, so I went ahead and installed it and it works perfectly. Here are some details if anyone else is interested:
- If you tuck your head under the back bumper, you will see the power supply to the plate lights pretty clearly. It helps if you drop the spare tire to the ground or it gets in your way. The leads to the individual lights connect on the right of the plate area as you are looking at it (driver side). They are wrapped in your typical ribbed automative wire cover.
- Just before they come together, the lead from the passenger side light is held by a little plastic clip to a small metal flange that hangs down vertically from the body work (as opposed to the bumper). Just after the junction, the single power supply that is coming from the driver side rear corner is also clipped to this same flange.
- If you pop out this plastic clip after the junction without breaking it, you've got two things. After clipping the plastic loop (kind of looks like a zip tie) that holds the wire to the clip with a side cutter, you've got a fastener you can reuse to mount the relay. You also have a nice spot to splice into the power supply to the lights.
- I pulled the two wires from out of the ribbed cover and picked one at random. It doesn't matter which one. Tuck one back in and cut the other. Strip some length from both sides and attach female spade connectors. These will connect to the male spades numbered 30 and 87a on a standard SPDT relay. It doesn't matter which side you connect to which spade. You will not use spade 87, so you can tape that off if you like (I prefer to put a female spade connector on it that isn't attached to anything).
- Next, pop off the driver side tail light assembly. There are two bolts holding it on that you can access with the rear door open, and then some snaps so you have to pop it off with some force. There should be a red wire in there, three green wires and a number of black wires. You want the red wire, but just to confirm in case your wires aren't colored correctly, you want the live wire going into the reverse light, which is the middle bulb.
- Splice a line into this red wire between the bulb and the junction. You will notice a small gap at the bottom of the body work behind the rear tail light between the body and the fender. Drop the splice down this gap and it will drop nicely behind the bumper/fender, and you can feed it over to where you are putting your relay together.
- Cut to length (but leave a reasonable amount of slack for changing rear tail light bulbs in the future - you need to be able to take the assembly off again without your splice snagging) and pop another female spade connector onto the end of your splice. You will probably also want to use this line to power your rear view camera, so keep that in mind too and leave some room to run another splice as well. You want to attach this to male spade 86 on your relay.
- The last thing you have to do is ground your relay. I drilled a small pilot hole in the metal flange mentioned earlier, and grounded to that with a self tapping machine screw and a ring connector on the end of a small length of wire. I also grounded my camera to this spot on a separate line directly to the screw. This ground needs to be connected to male spade 85 on your relay.
- The relay is now fully wired and ready to go. Most automotive relays will come with a rectangular metal piece for fastening. I fastened it to the pre-existing hole that the plate light power line was secured to with that plastic clip I saved from earlier.
- Now your rear plate lights will work just as they did before, except when you pop your vehicle in reverse, which will turn them off. Taking your vehicle out of reverse will turn them right back on (assuming your side lights or headlights are on of course).
