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Roadmaster Tow Bar Wiring Kit Installation - 2018 GMC Sierra 1500

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How to Install the Roadmaster Tow Bar Wiring Kit on a 2018 GMC Sierra 1500


Hi there GMC owners, tenure 2018 GMC Sierra 1500. We're going to be taking a look at and showing you how to install Roadmaster's Diode Wiring Kit. These come in various configurations, depending on the cable that you want to use. You can get it with a straight cable, which is great. if you have tow bars with channel management for your cables. There are coily cables, which is great if you have a tow bar that doesn't have any type of cable management.

There's also a hybrid cable, which is what we're going to be showing off today. And that's great if you have a tow bar that has cable management, but might have a high, low adapter or something, that's extending the length further. So you need a small coily section to make sure you got enough length. You can also get this in a four flat or a four round configuration, just depending on what connectors you've got at the back of your motor home. And this is what our diode wiring looks like when it's installed.

That's right. You can't see any of it because it's hidden behind our taillight assemblies here. The diodes will allow you to take the motor home signals that you've got your lighting signals on your motor home. Transfer them to the lights back here to illuminate these lights. The diodes will let that current flow from the motor home to the light, but it prevents it from back feeding into any of the electrical systems on your vehicle.

So you don't have to worry about causing any potential electrical damage. This gives you all your necessary lighting signals, which includes your left turn signal, right turn signal, tail lamps, and brake lamps. And I went ahead and turned on the hazards just so you can see that both sides are working on the motorhome and they're mimicking exactly at the same time back here on the vehicle. Diode wiring is my personal favorite type of setup for getting lights here at the back of your vehicle. There are a couple of options.

You could also get a magnetic light kit, which is lights that you just stick on top of your vehicle, they just kind of stick right onto the roof there. The problem with those is that every time you, you have to get them out, you have to set it on the roof and then you got to run the wire up to the front, to plug into your motor home. They are kind of just a hassle to me. And then on the bottom of those, they do have a, a non-scratch pad on the bottom for the magnet on your roof. But I found over time that kind of wears out. And eventually you're going to start to get some swirly marks on top of your roof. So I really just don't particularly care for those. I think those are great for maybe if you you're like you tow vehicles or something easy to put some lights on there real fast, like one time, those are fantastic. But for some you're gonna flat to all the time, this is a much better solution. There are also bulb and socket kits, which will let you add an additional bulb inside your tail end assembly, to light those lights in here. That way you don't have to touch any of the wiring on your car, you're just running it to a bulb, but you have to drill a hole into the taillight assembly when you add that bulb. And that's just another potential chance for moisture to enter in your assembly later on down the road, which can get quite costly to replace taillight assemblies. In certain states, you can fail safety inspection because of it. I also don't like them just because it's a regular incandescent bulb. It's fairly large and there's just not enough room in a lot of your modern taillights for them. So the diodes really to me are just the most elegant solution that is to me just the best cause it's once it's installed, it's on there. You simply just plug into your motorhome and you're ready to go. So here we are at the front, you can see our coily cable that we're using from this kit here. It plugs into our seven way here. Then the straight portion here goes through the channel here. So this is that hybrid cable. And then it just plugs right in. You got a six pole on that end, which is the most common for a flat tow setup is your six pole connector. You only really need a four pole connector to get all your lighting signals. But if you want to add additional accessories, like a charge line kit, which is required on some vehicles, you would want to go with the six pole. So I usually recommend just get the six pole out the gate. It doesn't really cost a lot more money, a couple extra bucks, and you can get that six pole instead of the four pole. And you've got a lot of opportunities in the future for additional accessories if you find you might need them. You can also get the diode wiring kit with no cable. If, that's great, if maybe you bought a new vehicle and you're going to reuse some of your old components from that last one, it's also nice for that. So now that we've covered some of the features of our diode wiring kit, why don't you follow along with me And we'll show you how to get it installed. It's something that you can do probably in your driveway. I'd say in about maybe two and a half hours, but I highly recommended that when you're installing this to do it, when you're doing a full flat tow set up, like putting your base plate on and stuff, because you'll have a lot of these front end components off like your bumper and the grill and all that, which makes it a lot faster to get this installed while those components are out of the way. That's how we're going to be doing it today and you can just follow along with us. It is a one-time install. So once you've got it installed, it's as simple as plugging it in for there. We'll begin our diode installation here at the back of the vehicle. We'll need to remove both the driver and passenger side taillight assemblies, so we can tap into our wires in there. Our two screws that hold it in place. You'll use a T 15 Torx to remove them. After you remove both the screws, the headlight assembly, or the taillight assembly, we'll pull straight rearward. So we're just going to- there we go, get the top, get the bottom, and we'll bring it back. We'll disconnect our connector here. You do have to push back on the lock tab here. Even it's pretty stiff. So you might need something. We can maybe use one of the screws that we just. Nope we're going to need a screwdriver to pop that. You've got a lot of dirt in here and it gets real stiff. So we'll grab our screwdriver here real fast. Now that we have our screwdriver, we're just going to push that tab towards the rear like that. We can then press it on the release tab and pull our connector off. This is a bolt in here. It doesn't have a connector. It's just hardwired to the bulb socket. So turn it counter-clockwise and then slide the bulb out of there. We're just going to put that down there out of the way. And we'll set that aside. The other side, we'll remove the same way. This does reveal the wiring though, that we need to access for our diodes. We're going to be putting those in about right here. So let's see. There should be a spot here on the conduit where it's open. We can just pull our wires out of there, just like that. So we've got access in here to our wires. We'll take some of this tape off of here. There we go. So this is the connector we need to slice into here. If we look at this connector, you can see we've got green, black, red, and brown for the wires. The ones we're concerned with are the green and the brown. But down here, you're also going to have the wires for this. So look at these it's two black, and then it's a lighter green color. So we want the darker green down here. So here's the darker green, here's the brown. Those are the two wires that's going to our lighting socket that we need. So we just separate those two out and we're going to cut both of these wires. After we cut them, we'll strip back each end of these wires. Once you go to the strip back on your diodes, you'll have three spade terminals. We're going to need a total of four spade terminals. We want the blue ones. One of your diodes has a yellow spade terminal. We are going to be using that one but not just yet. So we'll save that over here. We'll then take each one of these wires that we just stripped, twist the wire just makes it a little bit easier to push it into the connector. Slide our spade terminal over our wire. And then we'll crimp this down and we're just going to repeat this now for the remaining three wires that we have stripped here. So now you're going to have a bunch of wire that comes in your kit. This four-pole wire here. We need to start feeding it to our lights, and then we're going to route it forward. On the driver's side over here, we want the white, brown and yellow wire to feed up over here, but we don't need the green on this side. The green is for the passenger side. So we're going to take our snips here. We're just going to cut between the green and yellow wire. And then we're just going to peel back this green wire. You might want to peel back a couple of feet, cause this has to route all the way over to the passenger side the green does. But over here on the driver's side, we need these three wires. So now as I get this peeled back we're going to feed our wires up through the bottom of our assembly. So I'm just reaching right up there. You can, you can see straight down and get your hand in there to pull these up. These are going to connect into our diodes. Our yellow wires are left turn signal, the brown wires, our taillights and the white wire is ground. But we're actually going to use a small portion of this white wire to jumper over to the other side. So to do that, we're going to take each one of these. We're going to snip in between them, just like we did with that green wire. And then we're going to just peel them back like that, to separate them out and strip back into one. We'll, then take a blue spade terminal, place that on the yellow wire. Crimp that down. And then the yellow spade terminal in our kit. This is the only one you get in the kit. And it's for this one connection here. For the brown wire and we're going to use again a small section of this white wire as a jumper. So we're going to twist two of these together because we're going to be taking a little bit of this white wire here, and we're going to run it to the passenger side, to take our taillight signal. That's going to light up this light over here and then jumper it to light up the opposite side over there on the passenger side. So that's why it's a little bit bigger and that yellow color indicating that it's a little bit larger of an opening on the connector there. Connect these guys down. Then we can start connecting our diodes. The they're labeled in and out. You'll have two in's and a single out. The out is always going to go to the bowl, which in this case is going to be our connector where it plugs into the taillight assembly. So we're going to plug the out in there. We want to reconnect our wires back together, so I plugged this into the brown one. So we're going to plug the other brown wire here, back into the end. The brown circuits that we had cut here on the vehicle is the taillight circuits. So we're going to take the brown wire with the white here and plug this into the other side of this diode. We're going to take our other diode out towards our bulb. So we'll plugged that into the green wire there, take the other green wire, plug this back to the in. This is our driver's side, stop turn circuit. So we'll take our yellow wire here and slide it in place there. And at this point you kind of can just start cleaning it up. We're going to put our conduit back on. We'll take our diodes. And I like to do with these is take the adhesive backing off. And then take the two diodes and just stick them together. And then we can kind of zip tie it right here to our harness. I also like to take this wire, pull it up just a little bit and zip tight as well to make sure that there's a little slack here so there's never any tension pulling on our wires that we just connected. So here you can see our wire where we passed it up through the opening. So we started routing it across. There's kind of a channel here that we ran it through and when we come out the channel here on the other side, you can kind of see where I've split my wire there. The green goes all the way across, right here. You can see the green wire goes all the way across to the passenger side and then here, you can see that white wire going over to the passenger side. So this is where, right here, this portion going over that way, that white wires connected to the taillight assembly. We just did that. So what I did was I took some of the white wire here and I took a section of it and I ran it over there. To help determine how long I needed this white wire to be. This green wire, I kind of just peeled the green wire back and kind of held it up in the back of the vehicle to make sure it was going to reach over to the passenger side. Then I folded the green wire back along my wire and found where the green wire ended. That's where I cut my white wire. Then I peeled the white wire back up to make sure it was the same length as my green wire. And then ran it across. We go above the spare tire there. Over here on the passenger side, on the other side of the spare tire, we just go through the same channel that's located on this side. It comes out through the channel and then we go up through the bottom there to get into our passenger side assembly over here. So now here on the passenger side, if we fed them up, we made the same connections over on this side, the green wire and the brown wire on our connector. So it's the same wire colors. So we just peeled those out. We snipped 'em, we put our ends on them. The only difference over here on this side is you don't have that yellow connector. The white wire just goes to a blue spade terminal and plugs in to our brown circuits here to jumper that taillight circuit over. So from here now we can put these taillight assemblies back in, and then we can wrap the rest of our wire towards the front of the vehicle, to our connector at the front. After pushing it back in, just reinstall your screws and zip them down. These don't need to be crazy tight. So now we'll take the rest of the wire and route it towards the front. So we go from where we kind of split our wires. We go over the spare tire, the cross braces here, you can kind of see the wire right here. Right there you can see a little bit, and then we just continue on bringing it forward. There's a factory wiring harness here that runs along the inside of the frame. We actually just follow that and zip tied to that harness because we want to avoid any moving objects like our suspension and stuff back here, anything hot, like the exhaust. So the factory harness has already routed in a way that it's going to avoid those things. So we just continue on forward from there. So when we come across the other side of our axle here, we then go along our fuel tank and we kind of poke it above the frame a little bit to stay on top of the frame. You can see here, we're going around these body mounts and we come down here. This is that white wire where we had cut it. I did peel some of it back to make it a little bit longer and accessible. If we look there's a ground hooked up right there. So we can actually hook to our white wire up right to this ground stud. So first thing we'll do is we'll take our ground wire and we need to prepare it and we're gonna strip it back. And I'm going to probably just trim off a little bit of this here, get a little cleaner, strip it back. And then we're going to crimp on the ring terminal that comes included in our kit. Ring terminal inner crimpers here. Slide our wire in. And then crimp it down. Then I'll take our 10 millimeter wrench and remove our bolt here. After we remove the bolt, we'll take our ring terminal that we attached to our white wire, slide our bolt through it. Make sure we put our bolt back through the ground wire that was previously attached to it. And then we're just going to reinstall this bolt. So now with our ground wire connected, we can just continue running our wire forward. We just zip tie it to this factory wiring harness that runs down the side of the frame and we pretty much stayed there the whole way. If there's any body mounts that we hit, we made sure to run the wire above the body mount, so it supports it. And we pretty much stayed this way all the way forward until we get to here. We then just peel this back out of the way and just poke it up into our engine compartment from there. Now, the first thing you might notice here is when we're starting this video, how does that I don't have a front end on the vehicle That's cause we just put the base plate on and after installing your base plate, before you reinstall your fascia and your front end components here, that's the perfect opportunity to do the rest of your flat tow accessories, such as your supplemental braking system and your diode wiring and things like that. You can rattle this, way easier, save you a lot of time. So there our wire comes up, we talked about pushing it behind that fender liner, where that comes out is right there at the back of the fire wall. We then just keep our wiring following factory wiring all the way towards the front. We poke it through an opening and then we come out the front here. Now you might think, "Hey, my truck has got a front end on it." Well, the best time to install your diode wiring is when you're doing your full flat tow setup. So we installed our base plate and to install the base plate you got to have all these components removed. Well, that's the perfect opportunity is after you get your base plate installed on here before you put your fascia and everything back on, I'd recommend doing your diode wiring and also doing your supplemental braking system, because it's going to be way easier to get all these wires and stuff out right here to the front. So now that we've got our wire routed here to the front, at this point, we will need to get our fascia re-installed. So I'm going to go ahead and get that re-installed on here and we'll show you where we're going to place the six pole connector that we're going to attach these two in our fascia. We're going to be mounting it in there. And then I'll also show you how to get all these wires on your connector and which ones they're supposed to go to in that connector. We're going to put our six way connector here in the middle. We're gonna use a one and a quarter inch hole saw to drill this out and that way this will slide right in here and we can just bolt it right to this location in the center underneath of our license plate. I'm just going to line this up right in the middle. Right there. And then what I like to do with a hole saw with plastic like this, after I get that first hole cut, I'll switch it to reverse. And you can actually get a little bit cleaner, cut in reverse with plastic because the normal direction wants to kind of grip and tear. This way, kind of glides and cuts a little better. And that's only for plastic, but that really works on your, those softer materials that you don't want it to bite and grab into. So now we get that cut out. Let's just test our fit. Like a glove. Beautiful. So now we've got that in there, we're going to mark the two holes there for our attachment points and we're going to use a quarter inch bit then to drill those out. So just marking out that hole on each side. So we know it'll line up. You can use this as a template, but it's plastic. So it's really easy to mess up the face when you go to drill through it. So that's kind of just recommend that you do it that way to ensure that you don't end up messing it up. And then we just need to get a hole big enough for our hardware to pass through. We're going to be using the hardware that comes in the kit here. So we're just going to use a quarter inch. That should be plenty big to pass this through, you can see there. We'll line our bit in the center of our marks. Same thing on the other side, sometimes be careful touching your bit there, they can get hot. It's right on the other side there just knock those off. Clean that up slum. Slide, our switch into place, and then we'll secure it with the hardware, we're going to be using the bolts that come in your kit. You do get three of these. Ones for the breakaway switch, others you can use for this. Normally these attachment self-tapping screws or with this being plastic, I recommend doing a through bolt. So we're going to push that through and we had to push the other one through on the back side, we're going to place one of these larger washers to give us plenty of meat to hold it and then a nylon locking nut. I flip it over for you so you could see this, but this, this bumper here is actually pretty heavy. It's something that I would recommend moving around with an extra set of hands. It's very easy to accidentally drop it or banging into something cause it's kind of awkward. It's just so long and so heavy. And then we can just these down now. Now with an extra set of hands, we'll take our bumper and we're going to put it back into position and now we'll just tighten all of our hardware back down and reinstall everything in reverse order of how we removed it. We're now under the vehicle, we're going to connect our diode wiring to our connector now. So first thing I'm gonna do is just kind of bring it over and zip tie this here, just to kind of hold it. In the location that will keep the wires safe, kind of help keep it out of the way. All right, there we go. And then we're going to trim off some of the excess. And I do like to leave a little excess we're gonna probably do something like that. That just makes it easier for adding accessories and any kind of repairs or things that you might need to do in the future. So we're just gonna trim that off there. Then we're going to take each of these wires trim in between them so we can separate them. And then we'll just peel back from one another from there. Make sure anything now and slide it on. Push that up there for now. And then we're going to strip back each of the wires right here. Now we've got them stripped now I can twist them. It just helps keep any stray strands from occurring causing any kind of potential short. And then we'll grab our small screwdriver and we're going to open up the connections there at the back. We've got four that we're going to be attaching. And there's six here. We want to start with the one labeled GD. They are labeled on the connector there. So we're just going to open it up. And then next we have our left turn and then right turn. And then the next slot we're going to skip. And lastly, we've got our tail lights and then our center pin is where you attach a charge line if you we're installing one, but we don't have one of those today. So now we'll just poke our wires in just matching up color to function. So white is ground, brown is taillights, yellow is left turn and they're just a stray strain that we we're talking about, and I wanna make sure I twist that in cause I could cause a short and this makes things happen weird. And then the green wire here is our passenger turn. So we're just going to poke them in and then run them down, a little bit more slack in there between them. We'll start with the backside one that's our brown one here, open up just a little bit more. So we're just going to poke it down into a hole and then just tighten down those screws. Right now that we've got all of our connections made, wanna grab some dielectric grease and put a generous amount here on the back side, this is going to just seal it up, keep out any moisture. So we have a long lasting operations of our connector here. You can get some dielectric here at etrailer, if you need some and we'll slide our boot on it and push it down on there. And then I also like to take a little bit of electrical tape and just take the boot on there. Just helps keep it from sliding off. It's probably not going to happen with this one. Usually, your connector is more horizontal, but this one would be in more vertical like this. It's likely going to stay on there pretty fine by itself, but we're going to put it on there anyway, just to make sure. You do get some conduit in your kit as well. We're going to put some of this on here just to protect it a little bit, make it look a little cleaner. And that completes our look at Roadmaster's Diode Wiring Kit on our 2018 GMC Sierra 1500..


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