Roadmaster 4-Diode Universal Wiring Kit Installation - 2018 Jeep Grand Cherokee

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How to Install the Roadmaster 4-Diode Universal Wiring Kit on a 2018 Jeep Grand Cherokee


Today on our 2018 Jeep Grand Cherokee, we're going to be taking a look at and showing you how to install the Roadmaster four diode universal wiring kit for towed vehicles. Whenever we're flat towing our Jeep Grand Cherokee, we want to make sure that we're safe, and that everybody knows exactly what's going on while we're driving down the road. So, if we decide to change lanes or even stop, we need our lights to mirror the ones on our coach. That's exactly what our diodes are going to do. They're going to allow the signal from our motor home to be transferred to the factory lights, so we're not going to have to worry about those magnetic lights, setting them up every time, because our diodes are going to be a one-time installation.As you can see, our diodes are not going to change the outward appearance of our Jeep as all. They're going to be completely hidden behind our taillights, and they're also going to actually help protect our Jeep's wiring.

In case there is a problem to arise on the motor home end, those diodes are going to prevent any kind of back-feeding and damage to the factory wiring.Our diode kit is going to come with a straight cord, with a seven way to a six way, that way we can plug in from our motor home and into the front of our Jeep. The thing I like about the straight cables is that if you have a tow bar that has the channels in it, you can actually route your cable through the channels, keeping all that slack off the ground. It just gives it a really nice appearance to it. Our diodes are also going to come with a six way plug to mount on the front of your vehicle as well as a bracket to mount it up. However, we used the bracket that was already on our baseplate.If you're looking for a lighting solution whenever you're flat towing your Jeep Grand Cherokee, our diodes are going to be a great choice, because it is going to be that one-time installation with no outward appearance, and it is going to protect your Jeep.

Now what we've went over some of the features and seen what they look like, let's show you how to get them installed.I want to start off by saying that we have our fascia removed, because we just got done installing our baseplate. That would be a really food time to do your wiring and braking system if you're going to be installing one. You're going to want to start out at the front, wherever you're going to mount our electrical socket. Make sure you leave just a little bit of excess wire sticking out, so later on, we can wire up the plug that's going to go on the front.Then you want to run your wire all the way towards the back, towards the taillights. I took my wire and since I have my fascia off, it makes it a little bit easier to see, but I ran it towards the driver's side and went underneath the headlight and to the engine compartment.

Had my wire come up, and I left myself a little bit of loop, because later on I'm going to be using this wire to tie into my supplemental braking system. I dropped it down so I could avoid the steering and suspension components, and then ran it up towards the back. So, I wire dropped down. I started going towards the back, and to help protect it from the exhaust, I put it behind this heat shield, just ran it along the frame, following the factory lines. Went underneath this cover and came out, went over towards the outside of the fuel tank, went over the filler neck, and I routed my wire over all the rear sub-frame and rear suspension.

Then I have it drop down right back here.Now, we're going to move up top so we can take our taillights out and get access to the wires behind it. If we open up our hatch, and we come to the inside edge here, we're going to find two fasteners holding our taillight in place. Grab a flat blade screwdriver. Going to be a small notch in each one of these push pins. We're going to come underneath that notch and pop out the center section first, then it'll release the tension. Then we can come underneath the outer section and pull the rest of it out. Once you have both push pins removed, you're going to want to grab your taillight and pull it straight back. If you go too much to the side, there are some pins that can break. We'll come to our connectors here. There'll be a little red tab. Going to pull it away from the connector. Press down on the black tab. We can disconnect the socket. We'll do that for this top one as well. Once you have them all removed, we'll set our taillight aside and we'll pull out the passenger side as well.With our taillight assemblies removed, I went ahead and turned on my headlights. We're going to need to test each one of the wires on each one of these pig tails to find out which one is our taillight circuit. I'll go through. I'm going to take my circuit tester. I'm going to check the pins inside to verify which one's getting power. Looks like it's going to be the small black connector, and it's going to be the white wire with the gray stripe. That's going to be our taillight signal. You're going to want to check the passenger side and remember or write down the color of wire as well.Now, we went ahead and turned our headlights off, and I have an assistant pressing on the brake pedal, that way we can isolate that signal. Again, we're going to take our tester. We're going to test each one of the pins till we get the signal. We find the large black plug. We're going to look at the corresponding wire in the back. It's going to be the white wire on the large black plug. That's going to be our brake signal. Now, we're going to want to test the passenger side as well. Now that we have all of our circuits figured out going to our taillights, we're going to need to separate each one of the wires in our four pole.I'm going to take a pair of cutters. I'm going to go right in between each one of the wires, just make a small cut. Then we'll take the end of it. We'll just pull them apart until we have four separate wires. Now, you're going to want to go and separate them as far back underneath the vehicle as you can. We'll keep separating them till we have four separate wires. We're going to get our wires up to our taillight area so we can make our connections. I'm going to use a piece of airline tube to help get the wires up. I'm going to feed it down in between the body and the bumper here, so it can meet up with the wires down below. Once we have the airline tube underneath, we're only going to be pulling up the yellow and the brown wire for now.I'm going to take my brown and yellow wire. I'm going to take some electrical tape and connect it to my pull wire so I can pull it back up top. We'll go ahead and pull all the slack out. Whenever you pull your wires up, you want to make sure that all the slack's out of there, we don't have a lot underneath. Go ahead and pull our pull wire off, and we can start making our connections. I'm going to go ahead and put a zip tie on the factory wiring here, that way it has a good anchor point and my wire won't fall back down. We're going to go ahead and start with our brake and turn signal wire, which if you remember is going to be the large black connector with the white wire on the left side. We'll connect our yellow wire to it. Want to pull that tape back some so we get access to the wires themselves, and we're going to cut this wire in half and strip back both ends.We're going to grab one of our diodes that has all blue connectors on it. We're going to take two of them off, then we'll crimp it onto the end of the wires we just stripped. We can take our diode, and you'll notice that we're going to have two inputs and one output. The terminal that's closest to the plug itself is going to go to the output, and then we'll plug the other side in the input. We'll take our yellow wire. We're going to estimate about how much we're going to need. We'll cut it off and strip back the end of it, then we'll crimp it into the other spade terminal on our diode.Now we can go ahead and move on to our brown wire. Now, that's going to be our taillight circuit, and if we remember, it's going to be the small black plug with the white wire with the gray stripe. We're going to hook it up relatively the same. We're still going to cut our wire in half and put two blue spade terminals on there. This time, you just want to make sure you grab the diode that has the yellow connector on it and we'll still plug our blue connector one into the end, and the one closest to the plug to the out. We'll estimate about how much wire we're going to need again for our brown wire. We'll trim off the excess, except this time we're going to hold onto the excess wire and we're going to strip back both ends.We're going to combine the wire coming from the top and the excess, and we'll crimp it into that yellow spade terminal. This'll get plugged into the other end terminal, our taillight diode. Now, the reason why we use the yellow terminal and we use the excess is because we're actually going to send this excess wire back down, meet up with the green wire, and connect it over on the passenger side. Now, the brown wire that is going to go back down and meet with our green wire, we're not going to have enough to reach all the way over the passenger's side. They do provide you with a butt connector in your kit, so we'll go ahead and take it and crimp it onto the end of my wire. Now I have some brown wire here that I had laying around, that I'm going to use to extend it. Now, if you need some wire, you can pick some up here at etrailer.com using part number 16-1-1. That's going to be for 16 gauged wire by the foot.With our two wires connected, I'll go ahead and take some electrical tape, wrap up the butt connector, hopefully preventing any kind of corrosion buildup down the road. But once we have this wrapped up, we'll set it back down, meet up with our green wire, and use the same method to get it up to the taillights and connect them. With all our diodes in place, we can put our taillights back in. When you plug them back in, you just want to make sure that you press down on that locking tab, and that it locks back in place.If we look on the back of our diode, you'll notice that it's going to have this backing paper on it. Going to go ahead and pull the paper off. It's exposed some double-sided tape. Since we have a limited area behind our taillight here, I'm actually just going to take the two diodes and I'm going to stick them together. They can sit behind our taillight when we put it in place. Whenever we put the fasteners back in, you want to make sure you put the base in first. Then we'll press in on the center to lock it down. We'll repeat that for our other taillight as well.We should have one more wire left, and it's going to be our white wire. This is going to be our ground. We're either going to find an existing stud attachment to it, or we can go to the bottom, nice, flat spot on the sheet metal. I'm going to cut my wire, cut the excess off. I'll strip back the end, then I'm going to take the included ring terminal from our kit, crimp it on. We can take the included self-tapping screw and go directly into the bottom of the frame here. When you tighten up that ring terminal, you want to make sure that it doesn't move, but you don't want to strip out the screw.Now would be a good time to tie up any loose wires underneath your Jeep. And if you're putting a supplemental braking system on, I would suggest doing that before you put your fascia back on. That's what we're going to do. Now that we have our braking system and fascia back in place, we can wire up the plug that's going to go on the front of our Jeep. We're going to start out with these four wires. We're going to need to separate them so we can get each individual wire, and we'll pull them apart. We don't need a whole lot, just maybe a couple inches or so. We're going to strip the end of each one of these wires.We can grab the six way plug out of our kit. We're going to pull the dust cover off the back. We'll feed our wires through, just push it towards the back for now so it's out of the way, then if we come to the back of our plug, each one of these terminals is going to be labeled. If we look at the top, it'll have a TM for trailer marker. Next to that, it'll be GD for ground, LT for left turn, RT for right turn. This top corner one will have an S. That's going to be for an electric brakes. Then the middle one will be A. That's going to be our power source. We're going to go through. We're going to connect all the corresponding wires to each one of these terminals.Now, whenever you're done, this is what your plug should look like. Starting at the top and going counterclockwise, you'll have your brown wire, then your white wire, then your yellow, then your green. Pull the boot down, but before I connect it back, going to put a little bit of dielectric grease inside of here. Just kind of fill up this entire cavity. Hopefully that'll prevent any kind of corrosion from building up, and prevent moisture from getting inside, damaging the connection. Fill it up. Then we come back. We're going to wrap the entire back section here with some electrical tape, helping keep that boot in place, and help seal everything up as well.In your kit, it is going to come with a bracket to mount your six way plug. However, we already have a spot that's on our baseplate here, so we're not going to be using the bracket that comes with the kit. I'm going to take a self-tapping screw. I'm going to screw my plug directly into that post that's on my baseplate. Our wiring is going to come with a straight cable as well. Now, the vehicle end is going to need to be wired up, because it's made to go through the chain holes on a tow bar so it can keep all that slack off the ground. But, we'll go ahead and show you how to wire it up now so we can make sure that our system is working properly.If we grab the plug here, we're going to want to loosen this large screw that's towards the two grab handles here. We don't need to take it out completely. We just want to loosen it up where it's nice and loose. If you look inside, there's a little gate there. That's what's going to hold onto our wire once we get everything done. We're going to loosen it up so that it's out of the way. Then if we move forward, we'll have a very small screw towards the plug end. Go ahead and remove this. You want to be very careful, because that is a very small screw and it's very easy to lose. But then we'll take our plug, we'll pull it out. We want to pass all our bare wires through the metal section of our plug. We're going to push it through more than we need, and we can start wiring up all the terminals on the back here.Now, these are going to be labeled as well. You just want to keep in mind that the S is going to be the blue wire, the T is going to be the brown wire, G is going to be your white wire, L, your yellow wire, and R is going to be your green wire. Now, the center pin should be your black wire. Once you have all your wires in place, we'll slide the plug back over. Want to make sure that that hole lines up, so we can get that really small set screw back in place. Once you get that set screw in place, we can come back to that large screw. We're going to tighten this down till it's nice and snug. You don't need to over-tighten it, because again, that gate's just kind of holding on to our cable to make sure it doesn't pull those connections out.With the cord assembled and everything else in place, we'll plug it in and hook up our tester to make sure that all the circuits are working properly. So, I'm going to turn on my lights on my tester to simulate my motor home. You can see that the running light circuit is working as well as the left turn signal, our brake lights, and our right turn signal. All we have left to do now is hook up to our motor home and hit the road. That'll finish up your look at the Roadmaster four diode universal wiring kit for towed vehicles on our 2018 Jeep Grand Cherokee.


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