Trailer lights

My trailer is original from 76',and the frame is boxed in, so it makes it pretty tough to rewire, as far as tracing anything, but I need to, so I was hoping someone could shed some light on the basics. My plug (that attaches to the truck)has four wires attached, green,yellow,brown, and white, but it is connected to 2 red wires, and 2 black wires ? Where they go I have no clue! I got under the trailer and all I could see is where the grounds are connected to the trailer. To make it even more confusing, when I pulled off the ten lbs. of electrical tape the last guy used on his custom instal I found the white wire from the plug(that goes to the truck) not connected to anything, and the two black wires coming out of the trailer attached to the brown wire from the plug that goes to the truck. Any help or diagram would be greatl. Thanks

Buy a new wire harness(about $20) then use a fish tape to pull the wires through. You might need to drill a bigger hole on the bottom at the rear of the trailer to feed the wires to the end of the fish line. Im assuming you only have rear lights and no side markers. although If you do, use the same method. I did mine with side markers. It wasn't that hard. If you dont have a fish tape you can always call your electrician friend. If you dont have one, figure about $60 at Home Depot.
As far as your original wiring... the yellow, green and brown go to the rear lights. The white is a ground and those red ones could be for the side markers. Im not positive on that without seeing. I would use a tester to find that out.
heres a fish tape.
http://thumbs.ebaystatic.com/pict/7588821037_2.jpg

Yep, white-ground, brown-running lights, green-r turn/brake, yellow-l turn/brake.

Thanks for the reply, ya I figured that my only option was using a fish tape, but I dont think I painted the picture well enough with the current wiring situation. So.... the common plug that you can buy for $10 is (yellow,brown,green,white) which plugs into the back of the truck.That plug is then connected to the trailer wiring that comes out of the front of the trailer(original wiring) is four wires, 2 black and 2 red. The white wire that comes from the plug, that you were referring to as the ground was not even connected ?? Currently, this is how its been and I have running lights, and when I step on the brake sometimes the rear lights turn off. When I turn the blinkers on, the trailer becomes a x-mas tree, and every light flashes. Is my trailer being grounded with my truck, instead of that white wire ? I have two side lights on each side of the trailer and four brake lights on the rear frame.

Sounds like a redneck wire harness. lol!!
Pictures of the trailer would help me figure it out more for you. The white wire should come from your plug and be grounded to the trailer. Im the kinda guy that likes stuff done the right way. I would just rip it all out and replace it all.
See if this helps you.
http://www.accessconnect.com/images/...y%20wiring.jpg
As you can see those red wires are constant power used to run your side markers and rear markers. Those lights should never be interrupted when applying the brake or turn signals. If the are they were spliced with the wrong wire. The best wire to splice that with is the license plate lights.

My trailer lost its running lights and I only had one brake light, but the turn signals worked great. I made the change to LEDs. I went to a trailer supply place, Hitch Depot in Monrovia, they're not the cheapest, but they've got it all. I bought 35' of 4-element wire and a new 4 pin round plug. I got some LED lights at another source, but found the same clearance lights at Walmart for $6.00, the brake lights I got at Extreme Engineering in Riverside. I wanted a nice ID bar light (the 3 lights at the bottom), but could only find one at Auto Zone, (you can't tell how cheezy it looks at night).
After getting the lights, connectors, wire for pigtails, shrink wrap, drill bits, stainless screws, electrical tape, band-aids, and a day, it cost me about $175.00. Not the $640 my boat mechainc wanted just to rewire the trailer not including the lights.
If you have a tube steel trailer, in lieu of using a fish tape, you could just tape the new wires to the old wires and pull them through. I ran my wires from one side, across the back and up the other side to the clearance light. I ended up with only 6" of wire left over. It's a bitch, but you'll feel good when it's all done.
Good luck!

Dumbandyoung, you pretty much nailed it on the head ! This trailers wiring is a joke. That diagram is exactly what I needed,I think I'll just make my own harness, and completely rewire so I know its done right.Thanks alot. 76miller.

Anytime brotha!
Goneboating has a great idea with using the old wires to pull the new ones through. And you'll feel great when its done knowing you will no longer have to worry about it. Just make sure you use stranded wire not solid when making your harness.
Good luck, be sure to let us know how it worked out.