Trailer Wiring and Light Replacement Demonstration
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Trailer Wiring Demonstration
Today we're going to be replacing the wiring on this trailer. We'll be replacing a 4 pole flat, as you can tell this one is pretty beat up and worn, so it has to be replaced. We're going to cut this wire off and we're going to replace this brown wire also. We're going to cut this loose and pull the rest of our wire through, on this trailer here it's pretty open so we can reach the wiring. Just in case though, if your wiring was run in conduit and you're replacing it, don't pull all of this out yet. We'll actually tie on the new wires and use these wires to pull them through. We're going to cut off all of this old wire here, and we're going to take off this old light too. I would like to point something out on this 4 pole flat, you'll notice there's actually 5 wires coming out of it. What's happening is on the inside of this pin, which is for the running lights, has two wires coming out.
The reason for that is we can split the running light circuit to both sides of the trailer. Mainly that's used on boat trailers and other light duty ones. What's nice about that if you have a running light on the side, chances are your running wire right next to it. You can tap into your wiring without having to make a wire go all the way across. It basically provides a short cut. This case we're going to run it all the way on one side and jump over since we have a small trailer and no running lights. Now we're going to tape our new wires to the old ones and pull it through the frame. It doesn't take much, just enough to make it smooth so it doesn't snag anywhere. Now we simply pull the wire through. Before we pull everything through, we're going to make sure we have enough leader to hang out. This unit comes with a pre-wired ground wire so we're going to leave it at its maximum length and this is where we're going to ground it at and we'll have a good idea of how much slack we need to leave. At this point it's a good idea to tape up all the wires together that way it will keep them from getting tangled with anything else. Since we have our ground here we're going to ground it but before that we're going to take this loop off for a smaller one. Since we have an existing ground that works pretty good, we'll use a smaller screw. Always give it a twist when you crimp it down it will make a nice tight fit. We'll re-install our screw but first we'll put a pit of dielectric grease on there to help protect it a little bit, electricity still flows on the ground and the less rust the better. Now we can pull the rest of our slack out.
We have our lights pulled over to the left hand side, we're using the yellow and the brown, yellow for left turn. We need to cut this wire to length about 1/2 to 3/8 inch. The wires then get stuck inside here there's a little strip in here that pulls against it and when you pull it back it catches so it can't come out and makes electrical contact. You bottom out the plastic and give it a little bit of a pull back and it catches. Same thing with the left turn signal. If you notice there's two holes side by side here. You could actually jump another wire from this hole here to another light, so it acts like a miniature junction box. This little channel here hides the wire so when you push it up against your frame it won't get mashed. Your light gets installed just like that. Before we bolt on our light we're going to clean this area out where the holes are that way it makes a good metal to metal contact with no rust and corrosion. You can use a file or scrape it if you're in a hurry but if you can use something more abrasive. You don't have to get these super tight, just snug them down and they'll be fine. Again we're going to use the old wire to pull the new wire through. Now we're back on the right side of the trailer and we'll do the same thing, we'll run the wires and install a new light. Now we'll install our wiring, green for the right turn and brown for the running light. One more final touch will be to run some loom clamps to the wire to keep it up closest to the bed. It doesn't touch anything, but it's better to keep it out of the way. At this point we'll reassemble our trailer and test out the lighting. We have our trailer wired up, lets give it a test run. Notice we didn't connect our truck to the trailer so we can make sure our ground wire is working. It's not a good idea to ground through the ball because it can be intermittent from bouncing around going down the road. First we'll test the running lights then the turn signals, then the brake lights. We'll do this for both sides. There you have it for our install of our trailer wiring harness. We used part # 475550, 440-L, and 440.
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