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Demco 4-Diode Universal Towed Vehicle Wiring Kit Installation - 2015 GMC Sierra 2500

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How to Install the Demco 4-Diode Universal Towed Vehicle Wiring Kit on a 2015 GMC Sierra 2500


Hey everybody, how's it going Today we're going to be going over and showing you how to install the Demco Diode Wiring Kit here on a 2015 GMC Sierra 2500. So this is what our diode wiring kit is going to look like installed. As you can see here we don't have any wires running over our vehicle here or any additional lights. The diode kit is actually going to use the same factory bolts here as well as the same factory taillights. Therefore, everything is integrated into one, this seamless package that we have from the factory. Now, there are a couple of different taillight wiring systems on the market.

We mentioned the ones that have the magnetic base. They sit on top of the body somewhere and we obviously have to droop some wires down our truck. Definitely not ideal. There's also other kits that require drilling into the taillights. We're not going to have to worry about either of those things with our diodes here, because again we're going to be using the factory bulbs and the factory tail lights.

So what our diode wiring kit is going to do, it's going to be designed for when we're daily towing our vehicle, and simply put it's going to transfer these signals from our motor home to our towed vehicle. That way we can let others around us know what's going on and what signals we're going to be making. It'll transfer the most basic signals such as the stop and turn signals as well as the running light circuit. So keep in mind, we do have to splice into a few of the factory wires in order to get this kit installed. However, because of the integrated diodes, we don't have to worry about any issues with the motor home transpiring over and affecting our vehicle's lights.

Everything is going to be isolated due to the diodes preventing the back feed of electricity. So one of he other reasons I really like this kit is going to be in regards to the umbilical, which is simply the part that bridges the motor home to the towed vehicle. So the reason I like this is the durability of our umbilical. It also has a coiled design. So with this coil design it's going to help keep things nice and tight to the bottom of our tow bar.

Therefore, we don't have to worry about it dragging the ground and becoming damaged. Furthermore, it's also a seven way to six way adaptor. So most of the time, you really only need a four way to transmit the actual signals but there are certain cases where you may want to run a charge line through the umbilical cord. And this option allows for that. It will simply plug into the seven way we have on our motor home. And then we'll wire up a six-way to the diodes on the towed vehicle. And then everything is plug and play from there. So in regards to installation, this one is not bad at all. It really shouldn't take you that much time or effort to do. Everything's pretty straightforward. We're going to mount a trailer connector up at the front of the vehicle. We're going to run a wire from the front of the vehicle to the rear, and then we need to make a couple splices into the factory taillight circuit but that's pretty much it. Let's go ahead and walk you through that process now. So to start our installation here, we want to find a good place to go ahead and mount our trailer connector. So for our particular base plate kit here, it actually came with an additional trailer connector bracket. A lot of the base plate kits do have this. We're using the Demco one. So if this is the one you're going to be using you're going to have this bracket. We can show you exactly how to install it. If you have a different base plate kit with a different trailer connector bracket, these next couple of steps could vary a little bit but most of them are fairly similar. So you should be able to use this to help you out. So what we did for our trailer connector bracket, for the Demco one, there's going to be two holes on each side, we went ahead and just cut off the rear holes to flush up the bracket. And we mounted it directly to the bottom, sort of the flange to the license plate into this plastic air dam. So we just ran two self-tapping screws up through those holes and then into a metal support underneath the bumper there, you can see it's nice and solid. But once we have that mounted, we're going to go ahead and cut off the four-way that comes on our umbilical cord. And then we're going to route that to the rear of the vehicle. So this doesn't come in your kit but you can pick some up separately. We just have some wire loom here that we've placed over this first couple of feet of the wire here just to help protect it in the engine Bay. But we have it ran over here, lift up along, over the top of the frame. So depending on what braking system you're using, some of them require you to splice into the taillight wiring circuits. If that's the case then you're probably going to want to run the taillight wires up into the engine bay and make a loop up there, tie it off, and then bring it back down. If your braking system doesn't require this then you don't have to worry about that. But right about here is where we came out, where we made our loop. And then we're actually going to go into the frame. We can show you that on the other side here. And then we basically just ran the wire from this point in the frame all the way to the other end. So here you can see our wire entering in the frame, we're directly above our sway bar here. So there's going to be several of these little access points throughout the frame. Basically, you're going to have to use these to get the wire all the way back to the rear. And you're not just going to be able to push it through there all the way back. You'll have to take a piece of a little bit sturdier material such as an airline tubing, you'll tie one into your wire and then you'll push the airline tubing down the frame until you can get it to come out one of the access holes. And you'll simply just repeat that same process all the way down. So now we're over here at the rear of our truck. You can see that we have the remaining of our bonded four-pole hanging down. So there's going to be a large circular access hole directly behind the bumper, above the leaf springs on the outside of the frame rail. And that's where we pulled our wire out. Now, what we're going to do next is we're going to remove our taillights and then we can fish our wire up in the taillight housing pocket. So we're going to start first by removing the driver's side taillight. We're going to need a 15 millimeter Torx bit. And we're going to have two Torx screws here. We're going to take those both out now. Once we have both of those screws out we should be able to pull the taillight out and away from the vehicle, just like that. So now that we have the taillight pulled back and away. what we're going to do is we're going to remove each of these bulbs here. We'll just simply turn those. There's a little diagram here that shows you which way to turn it to remove it and then just pull it straight out. We have one more. And now we'll go ahead and set this aside and we can repeat this same process on the other side now or we can do it a little bit later when we ran our wire over there. So now all I did was I went underneath and I grabbed that bonded four pole. And it's super easy. You got a straight shot up into a nice open pocket here that we can use to run our wires up behind the taillight here. And what I'll do next is I'm going to take a zip tie. And I'm going to tie it to our wiring harness here. So I don't have to worry about the bundle of wires falling back down. So now that we have our four wires pulled up here behind the taillight pocket what we're going to do next is, there's going to be a piece of electrical tape here holding it on at this connection. We're going to remove that. And we're just going to simply remove some of the loom because we have our three wires here. So we've already tested these four. You put the brown wire, is going to be for the taillights and the green wire is going to be from the stop slash turn. So since we're over on the driver's side here we'll be attaching the yellow wire to the green wire, the brown wire to the brown wire. We're going to ground the white wire. And then we're going to run the green wire along with a jumper wire for our running lights over to the other side of the vehicle. So now let's go ahead and make a couple of these connections so we can show you how. I want to make sure I give myself plenty of extra to work with. We'll clip off the excess. And we'll strip some of the jacket back. And then we have two terminals that come in our kit here, two size spade terminals. For these larger diameter wires we're going to be using the blue ones, for the smaller diameter factory wires, we're going to be using the purple ones. So I'll just go ahead and crimp one of those on now. Now we're going to take the stop slash turn signal wire which is this green one. I'm going to cut it at a good point here. I'm going to splice on a spade terminal, the purple one, onto each side. Now we're going to take one of our diodes here. So the outside is going to go to the bulb. Just slide that on, the one on the inside is going to go to the factory wire that we removed previously. And then the other one will go to the wire from our diode system, just like that. Now we're going to repeat the same process for the brown wire, which is for the running lights. But as we said earlier, we actually need to install a jumper and run that over to the other side. So we'll splice on our two purple spade terminals and then we'll hold off for this one because we'll show you how to get the jumper wire for that. So in order to run our jumper wire from one side to the other, for the running light circuit, we're going to take the extra wire that we cut off from here. We're going to go ahead and strip off some of the ends of it. And we're going to tie it back into the circuit, just like, so, and then we're going to attach one of our blue spade terminals. Then we can go ahead and attach our last diode over here. So again, the output side goes to the bulb and then it doesn't matter which of these goes where. Now what I'm going to do next is I'm going to take our green wire and our brown wire. I'm going to drop it back down on the pocket here because we're going to be running it to the other side of the vehicle. And then we have one more connection that we need to make over here before we button everything up. So our white wire here, remaining over on this side, is going to be for a ground. So what we're going to do is, I'm going to clip the XX off, and then I'm going to crimp on the ring terminal that comes in our kit. We get a self tapping screw as well. Just going to splice that into a bare metal surface here, behind the taillight pocket. Just like that. So now I'm going to reinstall our taillight here and we can jump on over to the other side. So here we are on the other side of the vehicle here, we have our brown and our green wires ran over here. We're going to attach the brown wire from our diodes to the brown wire from the vehicles wiring and then our green wire from the diodes to the green wire from the vehicle's wiring. So we're basically just repeating the same process on the other side of the vehicle here. And now that we have all our connections we're going to go ahead and reinstall our taillight. So now we're ready to attach our six pole connector here. So we left ourselves plenty of extra wire from before. But what we're going to do now is we're going to trim mode down because we don't need all that. So we can just cut these all at once. It shouldn't matter. And then we're actually gonna slide on the boot here, push that back through there. And now we're going to begin stripping each of these wires so we can attach it properly to the back of our connector. So the green wire, we know that's going to be for the right hand, for the right side stop slash turn signal circuit. So we're going to take a look at the back of our connector here and look for the RT. So the RT terminal is that one there. So we're going to take a Phillips head screwdriver. You're going to need a smaller one. We're just going to back that bolt out a little bit, or screw rather, and then we can attach it like so. You wanna make sure that your wire doesn't fray like it just did there. You don't want any of these signals jumping circuits. And we'll just tighten that down to secure the wire in place. And now we'll just go ahead and repeat that for our remaining circuits. Now before we seal everything up, let's go ahead and test out our lights here to make sure everything's working correctly. You have our taillights here. We have our left turn, our brake lights. Now let's jump over to the other side to make sure that's working as well. So here over on the passenger side, we have taillights, brake lights, and then right turn signal. So before I secure the trailer connector to the bracket, I'm going to be taking some silicone here. I'm just going to be filling in all these connections here. That way we don't have to worry about any water getting in there. From my experience, if you don't do this, chances are, water is going to get in there, corrode your terminals and give you problems with your lights. So this is definitely a worthwhile step, something I recommend. So we'll go ahead and close that on there now. And now we'll just take some hardware to attach it to our bracket and that's going to do it today for our look at installation of the Demco Diode Wiring Kit here on our 2015 GMC Sierra 2500..


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