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Trailer Wiring Harness Installation - 2013 Volkswagen Passat

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How to Install a Trailer Wiring Harness on a 2013 Volkswagen Passat


Today on our 2013 Volkswagen Passat, we have our Modulite HD plus circuit protected trailer light power module, part number 119190. We also have our Modulite wiring kit to run power to our module and the part number for that is 118151. I just installed the hitch so I have some of the stuff out of the trunk already. You want to take our your spare tire, your jack kit and your floor mats, I have those out already so I'm just going to take out threshold piece here, I've got my removing tool. It just pops up and out of the way. Down on the bottom, on the inside, when you pop the top off you want to pull up on these and it'll pull right out.

You want to pull out these foam pieces and now we want to take off our carpet on this side and we have three push pins that screw out and pop out. I'm just going to use our pin removal tool and pop them out. You want to pop the center piece out, you may need to get a small screwdriver to pop it out enough to get behind it. Wiggle it in there and pull it out. You'll want to keep track of those because you'll put those right back in. The third one is right here.

We have one that's sneaking on us, remove it the same way. Now we should just be able to pull our carpet back and out of the way. Now that we're in here, what I'm doing is I've got my trim removal tool, I'm just going to pop our wire harness out a little bit so I can access the wires and then I'll use my circuit tester and I'll figure out which wire does what. You may have to remove some of our factory tape just so you can see the wires and get to them with your tester. What I'm going to do, I've got one of these bolts sticking up, I'll use that as my ground then I'll go and turn on my headlights so I can figure out which one's my running lights. I'll poke my wire and see if I get a reaction.

Okay, I do have power going through our black and white so now I'm going to turn off our headlights and see if the power turns off and our power turns off. That tells me the black and white wire on our 2013 Volkswagen is going to be our running lights. Now I'll turn on the blinkers. Turn on my left blinker because we're working on our left side, I'll test the same wire. We have our running lights and our left turning lights on our black and white wire.

I'm going to go and check the other ones. The gray and black does not turn on with our blinker and our brown does not turn on with our blinker. Our blinker and our running lights is going to be this white and black wire. We have somebody pushing our brakes, I'm going to start again with our black and white wires, see if that has our brakes on it. All three of our, blinker, running lights and our brake lights are all on this black and white wire. I grabbed our module, I looked at the instructions and this is a multi-plex functioning sales system so we won't end up using our red and brown wires at all. Our yellow wire runs to this side which I'll crimp in here. Our green wire, I'll run along the back here and run it to the passenger side taillight. Our white wire's our ground and our black wire, I'll use the other kit, the 118151 kit, to run power to this all the way up to the battery. Right now I'm going to use our crimp connector here, I've already got it over our black and white wire, I'll just slide our yellow wire in here making sure it's all the way through, I'll use some pliers, crimp it down, making sure that that metal plate that's sticking up goes all the way through. Now I can close the cap on here and lock it in place. Pull on the wire and it's not going to come out. Now I'm just going to run our green wire, just lay our green wire up here for now. I'll pull out the pins the same way I did on this side, I'll do it on this side, that way we can get to our taillight. Now that we have our pins out of the way I'm going to pull this out of the way like we did with the other side. On this side we do want to be careful because we do have the solid plastic piece here, we also have our light which has a harness right here. I'll squeeze these together and just unplug our light. All right, I pulled this out of our taillight. We've got a key that we have to slide back. When it's plugged in it's locking it in place so pulling this back allows me to push in on our pin and release our light. I'll go ahead and test our wires and see which one is our multi-plex wire. Got our headlights on already, I'll just test each wire until I find our headlight. Looks like our gray and red wire is going to be our multi-plex wire. Brown does not have anything and . We have power to our gray and red and our black and red. I'll go ahead and turn the blinkers on and test to see where we have power there. We have our blinker power going through our black and red. We'll test the gray and red. I've got nothing there. I'll test our brown wire and we got nothing there so we're going to be dealing with our black and red wire here so we've tested the brakes and it is that black and red wire like we thought so I've got our connected on there already, I'll run our green wire through then I'll use our pliers to crimp down that metal plate in there. Now that we've got that pushed down, go ahead and close that off. I'm going to go ahead and I'll zip tie in this place because this will be covered by our rear threshold plate. If you decide to zip tie where I've got it, just want to make sure that this is going to pull up out of the way because this will stick through the carpet. I'm not going to fully tighten it yet just in case we need to move some wire to one side or the other so we can make it fit. I'll just get it close. All right, so our kit comes with a self-tapping screw and I've figured out where I want to mount this so I'll end up mounting this up here and I already checked underneath our plate down here and there's nothing underneath that will hit with our screw. I'll take our drill with our self-tapping screw and go ahead and drill that in place. It may not matter but depending on how much wire you have, slack wise, I always like to point our tail towards where our module's going to sit and then tighten it down. Now, we have to run our power wire from here to our battery in the front. We've got a grommet over here, I'll pull it out, may take some finagling but it does come out. I'll just take my knife, cut a little hole in the middle, I don't want to cut it too big because it does help seal if it's tighter, a smaller hole, as small as you can get at least. I'll run my wire through it, go over to our connector here, obviously we had to make the hole a little bit bigger, pull that through, I'll pull our wire back through backwards because we had already ran it through our hole. I'll suggest, when you get this all the way pulled through under the bumper, just like our other wire, I'll go ahead and wrap it with electrical tape to seal it. Now I've got our trailer wire pulled there, I'm just routing it for easy access by our hitch. It is coming out right by our exhaust so I'm tucking it underneath the heat shield and then I'll zip tie it up out of the way. I've run it above our hitch to keep it from dragging on the ground and then I'll put our little cap around the hitch for easy access. I'll zip tie this over here as well that way it just keeps it nice and tight over in this area so that it doesn't hang loose and catch on the exhaust or anything. Now that we've got that routed we'll go ahead and route our power wire. I'll tuck it around our heat shield and find a nice, safe, path underneath our suspension and the rest of the car. I've showed you that I ran our wire behind our heat shield over here, I've come out right here, I zip tied it to the far side of our frame pole here and I've run it around and come to the bottom side down here, I've run it around our bracket and now I'm just going to follow our brake lines all the way forward. I came out right past this bolt, I went up and came out right here. If you can't do that with just the wire, you can get an old metal hook or whatever stiff material you have laying around that will help you get it through. I'm just going to continue following our brake lines. We've got our plastic skid plate with 8 bolts, I've already loosened this one. I'll just go ahead and take the rest of these out and drop it out of the way so we can just follow along with our brake lines. Nice and easy, just follow along and zip tie every once in a while just to keep it from sagging. Now we'll find the route to go underneath our plate and up into our engine compartment. I'll just use some air hose that we have laying around as a nice, stiff pull wire. I'll install our plastic skid plate again because we're done underneath here. We've found our battery on the driver's side, I'm going to take my hose and I'm going to run it with the top corner and try and get it all the way down to underneath just so it's a nice, tight fit and hopefully not get anywhere near any of our heat sensitive areas on our engine. Now that I've found it, I made a hook out of metal, I stuck it up in there and I found the end of my hose, now I'm just going to make sure I've got it running in a way that I'm not going to put our wire next to something hot or something that moves. I'll route up and over our CV joint here and come out above that bracket. I'm going to stick my wire up into the tube and then I'll tape it in place that way I protect the end of my wire. It doesn't always happen that way but it's nice to do that when you can. I'm just going to wrap this a bunch to make sure if it gets caught on stuff I'm not going to lose my wire. Now we get to drop the car down again and pull everything up to the top of the engine. Now that we've got our wire pulled up I'm going to pull off the top of our fuse panel here, set that out of the way. This does have live power so you do want to be careful, remove all your jewelry, I took off my wedding ring just in case. You can hurt yourself. A big safety tip would be to disconnect the negative side on your battery. What I'm going to do is I'm going to zip tie this wire along here and then I'll put a terminal end, I'll find a smaller one that comes in the kit and I'll attach to our power wire here because if I follow this it runs directly to our positive side on our battery. I'll install our fuse right in line down here. I'll go ahead and take this nut off. Now that I've got that off and out of the way I'll cut this, so I've got my strippers, go ahead and take off a chunk, doesn't need to be a ton, about a quarter inch or so is fine, I'll always twist the ends, it helps keep the ends from fraying out. I'll stick my terminal end on here, grab my crimpers, crimp it down pretty hard and then I always check to make sure it's a good connection and if you have a heat shrink terminal like we have on this one, I'll take some heat and shrink that down after we're all done. We also need to put this in place and get a general idea of how much wire we need to cut off. I'll cut off about here and again I'll strip off the ends of my wire, about a quarter of an inch on both of these, the other end of our fuse wire and then the battery wire that we ran to the back of our car. I'll grab the butt connector that comes with the kit, slide that down in place, crimp this side down, stick this side in and I'll crimp that down. You can always use electrical tape, just as a water barrier. Start on the connector, wrap around and just cover the ends where the wires go in. It doesn't have to be a ton, just enough to block the water from getting in there. Rip that off and smooth it down. I'll stick this down in here, put this on, now we've got the terminal in place, we'll go ahead and put our original power wire back in place. Now that we got that tightened in, I'll zip tie these to the existing wires. I'll clip the tails off, I'll put our fuse box cover back in place, making sure that we keep our fuse there up and out so we can get back to it. I'm going to mount this in place, it comes with double sided sticky tape so that's what I'll do. I'll peel off the one side, I'll stick it to the back here, then peel off our other side and I already found a nice flat place so I'll just stick that right there. We'll come back in here, we'll pop our grommet back in place from popping it out earlier. This is our power wire that we ran all the way up to our battery up front. We've got our power wire to connect it to here but before I do that I just want to clean up some of the wires, zip tie them out of the way so we don't get some wires tangled up. We're going to take our wire, see how much I need, I'm going to clip it off with a little bit extra just in case we mess up, that'll give you a little bit to play with. Trip off the end, again, about a quarter inch or so. Then I'll take our little connector here, feed our wiring into it, sometimes it's easier to stick both wires in at the same time, sometimes you just want to do one at a time. In this case it's easy enough and stiff enough that I can just do both at the same time. Crimp it down, crimp the other side down and then pull on it, make sure it's not going to go anywhere. Now that we're done with this let's take our zip tie and zip tie it to the rest of our bundle and clip off our tail. That will complete the wiring. Now that we've got everything zip tied out of the way we'll tuck this back underneath the top up here, slide everything back into place. Something to remember, it may get in the way while you're trying to push it back in but whether you can get the pins in before or after, you do need to pull the rubber weather seal back over the edge of the carpet. That's on both sides. All that's left is we put our 10 amp fuse in and put our cap back on. Now we're just going to test our lights and make sure everything works. All right, I've got our headlights on so the running light should be on. Pushing our brake pedal so our brake lights should come on, left and right. Our left turn signal, our left turn signal should come on. Our right turn signal should come on now. That will do it for our upgraded heavy duty Modulite circuit protected vehicle wiring harness, part number 119190 and our battery wire Modulite kit, part number 118151 on our 2013 Volkswagen Passat.


Info for this part was:

Employee Zack K
Video Edited:
Zack K
Employee Joshua S
Video Edited:
Joshua S
Employee Chris R
Video Edited:
Chris R
Employee Andrew K
Video by:
Andrew K
Employee Jacob T
Video by:
Jacob T
Employee Dustin K
Video by:
Dustin K
Employee Jeff D
Installed by:
Jeff D
Employee Matthew S
Test Fit:
Matthew S
Employee David F
Test Fit:
David F

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