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Roadmaster Universal Diode Wiring Kit Installation - 2019 GMC Sierra 2500

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How to Install the Roadmaster Universal Diode Wiring Kit on a 2019 GMC Sierra 2500


Hi there, GMC owners. Today, on your 2019 GMC Sierra 2500HD, we're gonna be taking a look at and showing you how to install Roadmaster's diode wiring kit. Roadmaster's diode wiring kit is gonna take all the lighting signals on our motorhome and transfer them to the lights here at the back of the vehicle. I've got the hazard lights turned on and you should be able to see those at the motorhome as well as here at the vehicle, mimicking one another because it's just transferring those signals right to here. The diode wiring will ensure that the signals are transferred from there. You'll get all the wiring necessary to bring them from a connector at the front to the lights here at the back.

And the diodes will install inline on the wiring, which will allow the current to flow from the motorhome to the lights, but not backfeed into any of the wiring on our system. That's how our diodes work, as a one-way check valve for electricity, to ensure we don't damage any of our computer systems. And this is my favorite option for getting lights working here at the back of the vehicle because you just use your factory lights, so there's no modifications to the vehicle, as far as how it looks. There are a few other options out there from Roadmaster. There's one that is a bulb and socket kit where you would physically add your own bulb.

I don't personally like that option 'cause you have to drill into the light assembly and that just leads for potential leak points in the future. The other option is a magnetic light assembly, which you would set on top of the vehicle or on the sides and they would stick right to the metal surfaces. But the problem with those, is every time you want to using them, you have to get them out, hook them up, you have to run the wire all the way up to the front and then plug it in. And then over time, the bottom of those magnetic lights do have non-abrasive pads, but they will eventually wear out and then you can potentially get abrasions on your vehicle from them. So, this, to me, is just the best option.

That's also gonna be permanently installed on there, so whenever you're ready to use it, you just simply have to plug in your connector at the front. Here at the front of the vehicle, we've got our seven to six-way cable, which will plug into the seven-way at your motorhome and go to the six-way connector that comes included in your kit here at the front. The connector typically mounts to a mounting point on your base plate. This is a bracket that comes with Demco base plates that gave us a mounting location to install this. If not though, you do get a small bracket that you can just drill into a surface and attach it.

But if you have an option on your base plate, it's usually gonna be a cleaner setup, that's a little bit more secure. You do get the cable included with this particular kit, but we do sell it in a couple of different variations. So, instead of a coily cable, we have straight options, which is great for tow bar that have channels so you can run it down the channels to keep them a little bit cleaner and make sure they don't go off down the road. Now, our coil lead option is designed to be able to keep some tension on it, so it shouldn't drag the road surface, but the straighter ones are a little nicer. We also have hybrid ones, which have a straight section for your tow bar. And when you got a bunch of extensions and things like that piled up, it has a coil lead section to reach your motorhome there. There's five main components you'll need when flat towing your vehicle behind your motorhome. You'll need your tow bar, which is your connection between your motorhome and your vehicle. Your safety cables, which is the supplemental connection in addition to your tow bar. You'll need your base plate, which provides the connection point on your vehicle to attach your tow bar to. You'll need your diode wiring, which will take all the lighting signals from your motorhome and transfer it to the light at the back of your vehicle so people will know your intentions when going down the road. And your supplemental braking system, which will activate the brakes in the vehicle when you press them in your motorhome to help you come to a safe stop. And now that we've covered some of the features of our diode wiring kit, let's go ahead and head into the shop and we'll show you how to get them installed. We'll begin our installation here at the back of the vehicle. Go ahead and lower down your liftgate. And if you've got a cover like this, make sure you open that up. We're gonna remove both the driver and passenger side taillight assemblies so we can tap into the wires here to add our diodes. There's two fasteners that hold it in place. And we're gonna remove both of those with a T15 Torx. We'll zip that out of there, and we'll zip the next one out. After you've got those removed, you can pull straight rearward on your assembly to get this to pop out. We got the top one to pop, we got the bottom one, still in there just a little bit. Sometimes, you gotta kinda wiggle it and pull a little. And then we'll just pull that until it pops out of there. And then we're gonna go ahead and just kinda lay this down and then head to the other side to remove the other one. Once both of your assemblies are removed, you're gonna get a big, long, bunch of wire. There are gonna be four wires in here. We need to separate these out. I've already taken the green one and cut it back. The way I did that was just took my snips in between the two and just put a little snip in there. And so, you can see here that you just can peel these back from there. Now, the white, the brown and the yellow ones, we're all gonna need here over on the driver's side. But the green one, we don't need over here. So, that one, you can peel back a bunch of that and let that hang down below. We're then gonna take these wires and you can reach right down below and pass them up the hole underneath to get them behind your taillight assembly. So, after we've got them fed up now, we've got our brown, our white and our yellow here, we're gonna strip each one of these back. We'll be crimping a blue spade terminal on the yellow wire. And then the brown and the white wires here, you'll take and twist together and connect those using the yellow spade terminal. So, just slide your terminal on there and crimp it in place. We're gonna do the same thing with our factory wiring here. So, if you open up your wire sheathing here, you should find four wires inside. You'll have a brown, a darker green, there'll be a lighter colored green and a black. We don't want the lighter green or the black, we want the darker green. And if you're a little confused, you can look here at the lights and you can kinda see the difference in colors of greens there. You see, that's the two wires, make sure that it matches the color of those two that are on the bottom there, 'cause the middle one's gonna be our reverse light. And for whatever reason, they used a similar color. It's green but it's a different shade of green. And the top light is gonna use the same color as the wire we need. So, once you pull those two outta there, you're just gonna cut it in half and crimp a spade terminal onto each one. They're all gonna be blue from here on out. We're now gonna take our diodes and go ahead and plug those in. So, the out is always gonna go towards your lights. So, these are the two wires that are going to our lights. So, we're gonna plug one into one, and we'll plug one into the other. Now, since this is brown, that means on the other side here, we're gonna be placing brown on that one. Hook that in there. And then since the bottom one is green, we're gonna be hooking green into that one. And the green wire is gonna be our stop turn signal, and the brown wire is going to be our taillight circuit. So, now we're gonna take the wires that we had made here and run up and we're gonna plug those in. The brown and the white is going to be our taillight circuit and the yellow is our driver's side stop turn. Now, the white wire is really gonna be our ground at some point, but we're gonna use a small portion of that white wire to make a jumper over to the other side, so that way, we can get our taillights also operating on the passenger's side. The green wire, we're also gonna route over there to the other side 'cause that's gonna be the passenger's side stop turn and that's the wire that we left down below from the harness here. The green wire that we had, that was hanging down below, I went ahead and peeled back enough and just held it at the back of the vehicle to make sure I had enough to get over to this side. I did take that green wire and I folded it back along the rest of the wires, just to see how long it was. And then I cut out a length of white wire, that's attached over there, to be able to head the same length of white over there to run over here with our green. We ran it across the back and up through the hole, and then we can make our connections over here. And we'll show you underneath where we ran it. I figured we'll show you this connection first, and then we'll head down underneath. And you can see over here on the other side, it's pretty much the same thing. You're gonna peel out the two wires that we need from here, which is, again, gonna be the brown and the green. Green is gonna be the stop turn. Brown is gonna be your taillight circuit. They're gonna go to the out on your diode. You can see, the green wire, that comes over, plugs to the in, next to the other green factory wire for our stop turn. And then the white wire, which is our jumper for our taillight circuit, it plugs in the other side of the brown there. And then we put a cable tie on it to secure it there to keep these from bouncing around. They do have some double-sided adhesive on back that you could stick them, but the length of factory wires is pretty restrictive on where you can move it, so this is how I would recommend doing it. I pulled the backing off and just stuck the two diodes together. So, now we'll show you the path we took to route them. You can crawl underneath. We've got our lift here, so we're gonna start here by showing you the green and white wire. They come down right underneath here behind the bumper. That's where we've poked up the original wires. You can see that the white's going across and we just kinda stay above the hitch that's located here. Continuing to run the white and the green wire across, they kind of meet up in the middle with the rest of our wires. But once you get past middle, you should have just the green and the white wire left. And those are just gonna simply continue going on. Try to poke it up above your frame and everything 'cause we wanna avoid anything hot like our exhaust there. And it'll just poke up the hole, going up behind the other taillight assembly there. So, now that you've got all the connections made there at the back, the rest of our wires need to go up towards the front. We will stop along the way to hook up the remaining white wire that's continuing forward to the frame, so that way, we can get ground for the vehicle. And that's just gonna keep going. So, it kind of starts right about here. You're only gonna see the green, the yellow and the brown because we had cut off a section of that white to make that jumper that goes across. Our factory wiring is located right here on the inside of the frame rail. So, we use cable ties that come included with our kit to secure it to that factory wiring 'cause we know that's already gonna be routed in a way that's gonna avoid any of our moving components or excessively hot components. Once we reach the fuel tank here, right at the back, this is where we have the rest of that white wire. So, it was about here back, is where we cut off a section for that jumper. So, here we're gonna take our white wire that we've got left, that's gonna continue forward. Strip it back and place a small ring terminal on it that comes in our kit. You're gonna crimp it on just like you did with those spade terminals. We'll then use an eight-millimeter socket or a 5/16 socket, either or, to run our self-tapping screw here right into this cross beam to get our ground. Now, we're connected to ground on the vehicle, so now we've got all of our four wires here again, met back up. They're gonna continue following this factory wiring harness up above the frame rail, where it'll pop out on the other side of the frame, a little bit further forward at the other side of our fuel tank. Now, you're looking at the wiring here. This is on the front side of our fuel tank. There it is right there. This is about where the bed meets the cab here. So, you can see, we just poked it up and then it continues going forward there. Our factory wiring sits right on top of the frame right here. So, we just continued connecting it to that factory wiring and following that all the way up. That factory wiring goes all the way down the frame here, so you can cable tie it to that all the way. Now, at this point, once you reach your tire here, there is gonna be a point where you might want to deviate from how we installed ours. Our braking system doesn't require us to tap into these lights, so we continued keeping our wiring low, going forward. But if you have a braking system like the Stay-IN-Play DUO or any other system that requires you to hook into the diode wiring for your lighting signals, then you would want to run that up to the engine compartment, so you can more easily make your connections to that braking system. But if you're using like a most portable systems or the Air Force One like we are here, we don't need to tap into it, so we just kept following that factory wiring all the way forward. So, once hit the tire here, the factory wiring kinda just hangs out right behind the fender liner. So, we just cable tied it up, following that factory wiring around our suspension components here in the front. So, after we've made our way across, we do just kinda push it right up above our sway bar. And there's another cross beam here. Make sure we stay above the sway bar. The cross beam is where your under shield here attaches to, so it comes out right here. There's all four of our wires, and they're gonna go right up to where we're gonna mount our connector, which is located here. This mounting bracket comes with etrailer or Demco base plate, so you can use that to mount it up. Many base plates will come with a bracket to mount your connector. And we just simply mounted the connector here. I'll go ahead and pull it off though, so you can see the wiring where it's connected to the back. So, here we've got all of our wires run to the appropriate connector. I did also install a charge line kit on this, which we'll install to the center pin on a Roadmaster setup. If it's a Demco, it would hook to the pin labeled S, which is the unused pin that we've got over there. Now, all these pins are gonna be labeled, like the brown one here. It is labeled TM right underneath of it. TM is for our taillight circuit, which is our brown wire. So, you'll simply undo the screw a little bit, slide your wire in and then you'll have to strip it back, of course, and then tighten down the screw onto the wire. So, after our taillight, which is brown, we're gonna go ahead and rotate it to the white wire here. This goes to the pin labeled GD. So, run your white wire into GD there. And next we've got our yellow wire, which is the left turn and stop circuit. That's going to be the one labeled LT. Slide that in there and screw it down. And then our green wire is the passenger stop and turn circuit, which is going to go to the pin labeled RT. So, just unscrew that and screw that in there and you're good to go. This last circuit here is used for some auxiliary stuff. This would hook to your brake controller output if your motorhome has a brake controller. So, it's oftentimes not used, so we're not gonna be using it here on our vehicle. Now, once all of your connections are made, we can fill this up with dielectric grease. That's just gonna help to seal it up and prevent moisture from getting in there and causing corrosion on our circuit. We also have a dust boot that comes with our kit. You do wanna make sure you slide your wiring through the dust boot before connecting it to the connector. That way, when you slide it back through, it'll go into your dust booth there and seal it up. We can go ahead and use the hardware that comes with it to mount it up. You're just gonna use a Phillips bit for the screw and you'll use a 10-millimeter wrench or socket for the other side to secure those. And there's your little nut. It is an nylon locking nut, so you don't have to worry about it, coming off of there on you. Plug in and test out our system. You can plug this into your motorhome to test it out. Or you can use a test box, which what we're gonna be using today. Your motorhome's probably more likely what you have at home. So, we've got our six-way end plugged into the six-way connector, and then the other end is the seven-way, which will go into our motorhome, or in our case, our test box. So, now we're gonna go ahead and operate each signal and make sure that the lights at the back of the vehicle operate when we activate them. So, now we'll operate our lights. There, you can see our taillight's operating. Here's our left turn signal. There's our brake lights. And then we'll head to the passenger's side. Over here on the passenger's side, you can see the taillights. The passenger's side right turn signal, and the brake lights. So, now that we've tested our lights and they're all working properly, we're ready to hook up our vehicle to our motorhome, place it in flat tow and hit the road. And that completes our installation of Roadmaster's diode wiring kit on our 2019 GMC Sierra 2500HD..


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