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This Old Trailer: Finding and Fixing Wiring Shorts

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Written by:
Lindsey S

Edited By:
Leah B

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Finding and Fixing a Wiring Short Episode of This Old Trailer


Today on This Old Trailer, we are going to discuss electrical shorts on the trailer itself. Basically we are going to talk about if you plug up your trailer and you find out that you have a blown fuse and the tail light does not work, the running light does not work. We will go through this trailer we have here and try to find some problems with it and show you what to look for. Basically when you are dealing with a short you are going to look for physical evidence. And that means tracing the wire from the front all the way out back. So what is going to happen is basically we are going to start at the plug. Generally it is going to be somewhere down here that has a problem like it has extra extra long length here and it is going to be dragging on the ground so it gets some road rash in there.

Your running light and your ground wires could fray and touch each other causing a short that way. Just work your way on down and then a lot of times the wire lays against the steel of the trailer. Sometimes it is a vibration like this will cause that problem also. Or one of the wires, part of the wire will grind against the frame causing a short. There is nothing here so you just keep working your way down where the wire goes through the loop here or through the hole in the steel. If it is really tight it could vibrate and cause a short that way. Which is usually not much of a problem. Whenever there is wire lying on metal somewhere, always check there first for a short. And you can not really see it. Maybe just take your fingers and feel the wire. If you feel anything that is out of place, and we can feel there is something right here.

Let us pull it out and take a look. It looks like the gray wire has got a nick in it. It has been like that for a while too because it is a dark color it is not a shiny copper. All right we will go ahead and give this a quick fix. Basically we are just going split the brown wire away from the other two. And just pull it away just to get it started just like I did. Okay. And sometimes there is a small nick you can probably just get away with just cutting it in half and stripping the wires a little bit on each side. If you have got enough wire you can actually go ahead and just slice the butt connector right into place. If it was a little farther apart or a really big section like we are dealing with here you might want to go ahead and just put a small section of wiring and two new connections in there too. And this is right at the end so since these are kind of corroded up and your fresh wire is here, it is better to connect to that so let us go ahead and pull it out a little bit more and we will just put a new section in. Again, if there is just a one time deal then this is fine but if you are going to have like three or four of these places in your trailers, especially an older one, that has been sitting for a while, you might want to go ahead and just replace the entire harness because the more connection you have the more liability one of these coming loose. Start with fresh wire.03:27.

And actually this type of short is a perfect example of an intermittent short. Or sometimes you go down the road and you blow a fuse and then you put a new one in and it does not do it for a while, that is because these wires have been bouncing back and forth on the frame so when it hits the right bump, they will short out and you will not know what is going on. Okay, and we will just go ahead and just cover up our connection from the electric tape and we will give it a test. And this is only for our running light circuit. The short one that will not bother any other instances of left turn or right turn both have their own fuses on the vehicle. All right, once you have got your connection made, then it is a good time to go ahead and try it again. Now if this does not work again the chances are you might be dealing with another short somewhere else down the line. Chances are it is usually just one short causing the problem. We do not have our truck handy, we are just going to plug this into our own power supply. You could easily do this at home with a couple of wires coming off the back of your towing vehicle and just put the wires to the correct terminals temporarily testing it that way. All right, we have got our power supply on. We have got the running light circuit turned on. And so far it has not been shortened out but I think we are good with that circuit. It is always a good idea to inspect the rest of the wiring just in case. The same way we did before. 05:24



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This Old Trailer: Replace Wiring with a 7-Pole Cable

Today on This Old Trailer we are going to replace the wiring on this trailer. Right now, this trailer has a 5 pull socket here and the owner uses a patch cord in between here and his tow vehicle. What we are going to do is remove all this and add a 7-way cable that leads right to his tow vehicle. We will be using part number H20046. We will unbolt the connector here. Then we will go ahead and untape it and undo the screw right here, it should release the inside part where the pins are and the wires are connected. Tale that, push everything out. Simply disconnect our wires. 1:04



This Old Trailer: Wiring Trailer Tail Lights

In this edition of “This Old Trailer” we are going to wire up the lights on this trailer. Previously we had hooked up electric brakes and you can see, right now we have the junction box installed on there and we have wires ran for electric brakes. We have nothing for the actual tail lights themselves. That is what we are going to start on today. :30



This Old Trailer: Finding and Fixing a Broken Wire Part 2

Next we are going to go to less obvious stuff. Say for instance you have got your ground wire hooked back up to the frame and weird stuff happening out back. We will have to dig into the wire itself a little bit. In this case basically you want to check your wiring connection. You have a wiring connection right here that could be a potential problem right there. Chances are whatever fitting you used to put the wiring together might come loose. And also we have something kind of obvious too. The wire here has a little bit of road rash on it. You can see the bare wires on the inside. Even though it may still be making contact eventually this wire here will corrode up inside there and it will just lose contact so we are basically going to have a broken wire eventually. Lets go ahead and take this apart here we will see what we have got on the inside. 01:14



This Old Trailer: Troubleshooting the Full Ground Wire

We have demonstrated all of these fixes checking the ground on the trailer. The trailer itself is actually used as a ground obviously. Now there is some cases where you boat trailer guys and some small utility trailers out there, the ground is actually carried in a separate wire that lowers the trailer frame completely. The same tricks apply to check and make sure your light is working. Again the connection to the light could be bad or it could be actually a smashed wire underneath the frame of the trailer or also up front where you have got a little bit of road rash dragging the ground. We will go ahead and show you next an example of that type of wiring on a different trailer. 01:04



This Old Trailer: Troubleshooting the Ground Wire

The first thing you want to do when you first start working on electrical problems is you want to divide and conquer. You have two parts here, the truck and the trailer. You want to verify which one actually has the problem. Chances are it is going to be on the trailer, but then again you still want to check the truck too. So use a separate light tester, hook a ground not to the frame but to the 4-pull ground itself because this is what is going to carry the ground to the trailer. :52



This Old Trailer: Finding and Fixing Wiring Shorts Part 2

Now we will move on to another circuit. In this case it will be the right turn circuit. And we will just check the signal on that. On the right turn signal here again, the same principle applies. Start from the front and work you way back. What happens a lot is that on some of these lights here where the wire gets ran in behind it, there is a channel that these wires fit into. However a lot of times, even on brand new trailers. This wire actually does not fit in the channel, they miss when they put it together. The wire gets smashed between the light and the frame of the trailer. Eventually they wear down to a minuscule spec of wire that is visible but it will cause a short and all kinds of headaches.





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