bing tracking image

Roadmaster Universal Diode Wiring Kit Installation - 2018 Ford Fiesta

content loading

Products Featured in this Video



How to Install the Roadmaster Universal Diode Wiring Kit on a 2018 Ford Fiesta


Hey everybody, how's it going Today, we're gonna be going over and showing you how to install the Roadmaster Diode Wiring Kit here on a 2018 Ford Fiesta. So, a diode wiring kit, or just a flat tow wiring kit is gonna be one of the required component we're gonna need to remain legal when flat towing our vehicle. So, the wiring kit's pretty self explanatory. It's gonna transfer these signals from our motorhome to our towed vehicle, to let others out on the road know our signals. Because obviously sometimes we not necessarily see the lights on the motorhome. The towed vehicle could be blocking these.

Therefore we still need a way to transmit our signals to others on the road. So, this is what our diode wiring kit looks like installed. As you can see here, we don't have any other components on the vehicle. It actually reuses the factory taillights. So, that's one of the reasons I really like this kit.

There's certainly a couple different options you can choose in regards to a flat tow wiring harness. Some of the other more common ones, magnetic lights that you stick on top of the vehicle, such as the trunk. Now, those don't require any modifications to the vehicle, but the problem with those is, you're gonna be draping an electrical cord over the roof of your vehicle and attaching it to the front each time you need to tow. You also have to worry about the magnetic base scratching the paint. So ,those definitely aren't an ideal option.

Another option out there is called a bulb and socket kit. Those actually just drill into the taillights. So, they don't require any modifications to the wiring on our vehicle, but we do have to drill into the taillights. And these are probably my least favorite kind of flat tow wiring harnesses because drilling into the taillights, it's not necessarily a great thing to do, because it's gonna induce the chance for leaks which can erode the contacts and cause lighting issues with the factory lights. Now, also drilling into your taillights, you need to be pretty precise because if you don't drill in the right location the first time you really don't have a lot of options but to replace the taillight.

So, we won't go too much more into those, but we will go into a little bit more about the diode wiring kit, which is what we have installed here in my preferred flat tow wiring harness. So, we are gonna show you guys how to set up and install this, but essentially what's going on behind the scenes here. We have a wiring harness that we run from the front of the vehicle to the rear here. And then we splice into two wires on our taillights on each side. So, we do have to splice into the vehicle. However, what we're doing is, we're splicing inline a diode. And what that diode does is, it's gonna prevent the backfeed of electricity. Therefore, say we have an issue with the lighting on our motorhome. We don't have to worry about that carrying over and affecting the lights on our vehicle here. Everything is gonna be isolated from one another. So, we don't have to worry about any issues with the factory lights here on our Fiesta. So, in regards to the signals that we're gonna get out of this wiring kit, it's gonna give us all the basic ones we need to remain legal. We're gonna have our running lights for when we're traveling at night. And then we're gonna have our stop and turn signal circuits on both sides where we're traveling in the day and in night as well. So, there are a few different variants of this kit. There are some that actually come with the electrical cord but what I like with this kit here, it gives you the freedom that you're not purchasing extra parts. So, those people that have the tow bars with the integrated umbilical cord which is what we have here, this is the Roadmaster Nighthawk, for example. So, those actually come with their own connector for the vehicle. What's great about this kit is, here, we're not gonna have to worry about purchasing any extra components we're not gonna be using. It's simply gonna wire up to a trailer connector of our choosing. That also gives us a little bit more freedom in regards to which type of trailer connector and umbilical cord we want to run. So, in regards to installation, these are one of the easier flat tow wiring harnesses to install. They're obviously not gonna be as easy as the ones that stick on the vehicle but we talked about some of the shortcomings of those. They will, however, be easier than the bulb and socket kits that we explained a little bit earlier. So again, we're splicing into a few circuits of the rear of the vehicle then running a wire from the back to the front, wiring it up to our trailer connector, and then we're done. That's gonna be it. We don't have to worry about any other cutting into the vehicle or modifications. So, now we need to go ahead and take our bonded 4-pole harness. We're gonna tie it off to a front of the vehicle here where we're gonna be mounting our trailer connector. Most base plates are gonna have two little standoff tabs that we can actually mount the trailer connector to. If not, we'll just go ahead and loop the bonded 4-pole around the base plate. Make sure you give yourself some extra to work with, but now we're gonna route this wiring harness from the front of the vehicle all the way to the rear where our taillights are. So, for this first couple feet of the wire we're gonna use the included wire loom that comes in our kit. Then I'm just gonna simply zip tie it to the base plate kit here to hold it in place. And then we're gonna come up and over this little panel here, and if we come underneath this is the bonded 4-pole wiring harness. You see, we have another zip tie and pretty soon we'll run out of that wire loom there. So, our 4-pole wire's gonna come out up above the frame here or above the crossmember. You wanna make sure you avoid any of the axles or the sway bar, any of the moving suspension components. And here's where we're gonna come out at. So, you can see, I have another zip tie here. I pulled it nice and tight. And I looked up in that hole there that the wire wasn't binding up on anything. But now we're pretty much just gonna be following the brake and fuel lines to the rear of the vehicle here. You can pretty easily see the wiring harness. At this point here, we're gonna come over around the gas tank. Up and over the rear crossmember like so. And there's gonna be an actual pretty large access hole in the back of the frame. We fed our wire up through that, and then we came out this hole here and then I just looped it down and over the bumper beam like so. You can see, we have the rest of our wiring hanging here, and we're gonna leave this here until we get everything prepped back up by the taillights and then we'll pull that wire through. So, now we need to open the trunk on our vehicle. We need to remove both taillights. Now, in order to do that, up at the top here you're gonna have a little push pin fastener. We're gonna need to remove that. Now, those are on there pretty good, so you're gonna need a pry tool to get that out. But once we remove that we can go ahead and peel back this fabric liner here. And once we get peeled outta the way you're gonna see we have a thumb screw here. So, we can loosen that thumb screw by hand. We're gonna hold onto the taillight as well while we're doing this. And then we should be able to hold the taillight out. And there's one alignment tab back here we need to be sure that we pull out in a way so we don't break it. Now, we're gonna depress that little tab there on our connector and simply remove the taillight. We'll do that on both sides. So, we're gonna pull our connector back into the the hatch area here. And you can see we have this fabric tape. We need to go ahead and remove some of that to give us more room to work with our diodes. Now, this fabric tape is kina hard to get off. Really, the only way is to take a razor knife and split it, but we need to be careful that we're not piercing our wires at the same time as well. So, if you come through this way it gives you the best chance of not causing any damage to the wire. So, we wanna split off maybe around eight inches or so, just as much as we can get. The more we get off, the easier it is to work with our wires. We need to do this on both sides. So, we've got our 4-pole wiring harness pulled up into the rear here, where our connector is for our taillights. So, if we look outside here, you're gonna see an opening behind the bumper and the body panel here. That's gonna go all the way down to the underside of the vehicle, where we ran this wire below. We just simply took a piece of airline tubing. We taped it to the wiring harness down underneath and then we pulled it up through, into the taillight pocket. But once we have our wire up here, we can begin making our connections to our connector here. So, there's two wires that we're going to be using. The gray and orange one, that's gonna be for the stop/turn signal circuit. And then the green and purple one, that's gonna be for the taillight circuit. So, what we're gonna do is, we're gonna take a pair of wire cutters. We're gonna cut this orange/gray wire about halfway back. And then on the side, going to the connector, I'm going to remove some of the jacket on the wire. I'm gonna take one of our diodes here, take one of the blue spades off the diode and I'm gonna simply crimp it onto the end of the wire. I wanna make sure that crimp is nice and good and your connector isn't gonna fall off, but once we've done that we're gonna crimp another spade terminal onto the other end of our wire. So, now once we have that wire cut in half and we have a spade terminal on either side we're gonna take our bonded 4-pole wiring harness here. And what we're gonna do is, we're gonna be separating the yellow wire because we're gonna be installing that in line these two wires using one of our diodes. So, I just went ahead and made a cut on each of these wires here and I'm just gonna simply be stripping them back. So, the green one's first, and then we'll do the yellow. So, the next thing we're gonna do is, we're gonna take the yellow wire once we have it stripped free from the rest of the wires. Now, I'm gonna go ahead and give ourselves some extra slack here. We're gonna be cutting a lot of it off, but we still wanna give ourselves a little bit of room to work. So, I'm gonna cut that off. And then I'm just gonna splice on another one of those blue spade terminals. And I'll crimp this one on. Now, we can go ahead and hook up our diode. So, in regards to the outside of the diode the single tab that needs to go to the light. So, we're gonna be placing that on this connector here that goes to the pigtail. But aside from that, it doesn't matter on which one goes to the end. There's two prongs here. Just need to make sure you hook them both up Just like that. So, now we're gonna take the purple and green wire which is for the taillight circuit. And we're gonna be hooking that up in this same manner, but we're gonna be using the diode here with one yellow connector. So, everything's gonna be the same up until we get to the point where attaching the brown wire. So, we're gonna go ahead and repeat the same process and we'll stop there, so we can show you how it differs. So, we've got a spade terminal on both of our other wires for that purple and green. So, we told you there is one more connection that's gonna differ a little bit for the brown wire. So, basically what we're gonna be doing. You can remember, we cut off quite a bit of extra slack which is what we have here. We're gonna save this 'cause we're gonna be reusing it. Basically, we're gonna take two ends of the brown wire and we're just gonna tie them together like so. And then we're gonna be crimping on this yellow spade terminal. So, this is for the running light circuit again and we need to make a jumper wire that goes to the other side. And that's simply what this is going to do. So, therefore, this brown wire here and the green wire that we split apart earlier are gonna be running over to the other side of the vehicle. That's the passenger side. So, we'll go ahead and connect our diode now. And then we have one more connection before we start routing everything to the other side. So, the other wire we have to deal with before we route these to the other side is this white wire here. This is gonna be for a ground. So, what I'm gonna do is, cut off the excess we have. And then I'm going to crimp on one of the ring terminals that come in our kit. And that's what this little guy is. And then we should have a self-tapping screw in the kit as well. And we're gonna use that to ground this wire to a part of the body. So, we got our self-tapping screw on there. We're just gonna find a nice flat piece of metal on there we can attach the ring terminal. So, once we get all of our connections made, we went ahead and remove the adhesive backing from the diode. We just stuck it to a bear part of the metal there. And then we tied up all of our wires, so they don't get caught up in this spring, but now we're gonna reinstall our taillight and we're gonna route the green and brown wires over to the passenger side of the vehicle below the threshold panel here. So you can see, we have our brown and green wires ran over here to the passenger side. And we pretty much just repeated that same process. The wire colors over here, however, are a little bit different. The taillight wire is the white with orange stripe wire. And then we stop/turn signal wire is gonna be that green wire with the orange stripe. So, now that we have everything hooked up, we can go ahead and test our lights to make sure everything's working correctly. As you can see, we have our taillights now. Turn on our left turn. Our brake lights and then our right turn. So, there we go. Now, we know everything is hooked up and working correctly. So, now the last thing that we need to do, we need to go ahead and install our trailer connector. Now, this particular kit doesn't come with a trailer connector. Most likely, if you're selecting this option it's because you already have one such as the 6-pole that we show here. Some tow bars that have the included umbilical cord actually come with this. So, if that's what you're using this kit is gonna be a great option. But now we're just gonna follow the steps for the trailer connector manufacturer in order to get it installed successfully. In regards to mounting, this is again gonna vary depending on what setup you're going with. Most base plate kits, however, have two little standoff tabs here that we can mount it to. And that's gonna do it today for our look and installation of the Roadmaster Diode Wiring Kit here on the 2018 Ford Fiesta..


Info for this part was:

Employee Joe V
Test Fit:
Joe V
Employee Randy B
Test Fit:
Randy B
Employee Jared G
Test Fit:
Jared G
Employee Andrew S
Test Fit:
Andrew S
Employee Brent H
Test Fit:
Brent H
Employee Shane H
Test Fit:
Shane H
Employee Robert C
Test Fit:
Robert C
Employee Conner L
Test Fit:
Conner L
Employee David F
Test Fit:
David F
Employee Ryan G
Test Fit:
Ryan G
Employee Clayton O
Test Fit:
Clayton O
Employee Kevin C
Test Fit:
Kevin C
Employee Bradley B
Test Fit:
Bradley B
Employee Andrew K
Video by:
Andrew K
Employee Zach D
Video by:
Zach D
Employee Jonathan Y
Video by:
Jonathan Y
Employee Michael B
Video by:
Michael B
Employee Jacob H
Video by:
Jacob H
Employee Aidan B
Video by:
Aidan B
Employee Thomas T
Video by:
Thomas T
Employee Schuyler H
Video by:
Schuyler H
Employee Jeff D
Installed by:
Jeff D
Employee Joshua S
Video Edited:
Joshua S
Employee Jacob T
Video Edited:
Jacob T
Employee Kathleen M
Video Edited:
Kathleen M
Employee Dustin K
Video Edited:
Dustin K
Employee Chris R
Video Edited:
Chris R

At etrailer.com we provide the best information available about the products we sell. We take the quality of our information seriously so that you can get the right part the first time. Let us know if anything is missing or if you have any questions.