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Trailer Wiring Harness Installation - 2011 Volkswagen Jetta

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How to Install a Trailer Wiring Harness on a 2011 Volkswagen Jetta


Today on our 2011 Volkswagen Jetta, we're going to take a look at and show you how to install the Tow Ready T-One Vehicle Wiring Harness with the 4-pole flat trailer connector. Part number is 118572. Here we can take a good overview of exactly what the wire kit's going to look like. The center piece of it is going to be our modulite box. This is a module that's going to hooked directly in to our battery. This is going to prevent from any overloading for our vehicle. It plugs right in to the wiring harness.

The cool thing about the harness is that these have the exact fit plugs that are going to go in to the factory wiring behind the tail lights. Each one's designed to go right in to our factory connection, so we don't have to do much cutting or splicing or anything like that of any harnesses. The yellow and brown, that goes behind the driver's side tail light. The green and red, behind the passenger. The black wire that runs here, in to the already connected butt connector and through our 12-volt power wire's going to go to a 12-bolt power source and that power's our modulite box. We've got a ground wire, here.

This is going to go to an already existing ground in the vehicle we're we've got this small self-tapping screw provided that we can use to make that connection. Of course, this is what we're after, that's our 4-pole wire. That's going to give us turn signals, running lights, brakes to the rear of the vehicle so everybody will know which direction we intend to head. As far as hardware goes, we're going to have a handful of zip ties there. You may need a few more than what's there; a few longer ones. We'll see when we go through.

We've got a couple of our butt connectors, a ring terminal for making the connection to our battery and then, the fuse holder that we're going to put just before the battery to make sure that we've got a good circuit protection there. Also, there's going to be some double-side tape to get our box secure, as well as, some double-side tape already on the modulite box. A full kit of instructions here with illustrations, so they can point you the right direction. Fairly easy install to do. It'll just take you a little bit of time to get it done. To begin our wiring install, let's remove our spare tire cover and anything else that might be in the back of the trunk.

Then, we'll put out and up on our threshold and remove it. Now, we're going to take out the 3 fasteners that we've got; 1, 2 and 3 here on the side. Use a little Allen key. Just unscrew that middle core. See how it comes out. Set these aside. We're going to be putting them back in. Pull in just like that and hang that out. We'll see the plug right here in to the back of the light. We'll pinch our 2 tabs in there, we'll pull out to separate. Now, we'll take the yellow and brown side T-connector. As we mentioned before, exact match for our factory harness, so all we have to do is slide the ends together and listen for that click. Take the other side of it and place it right in the back of the light. Just like that we got our driver side connection made. Now, we need to decide where we're going to be mounting our module box. We'll go ahead and plug it in to the wiring harness itself. Just like our other connections, you want to hear that click. Let's find a good area where it fits in without any kind of interference. It looks like right down in this area we should have plenty of room between our trunk covering on the inside there and the outside of the car for it to go without any real issue. Set it aside for a minute. We're going to use a paper towel with a little bit of rubbing alcohol on it. We're going to clean that mounting surface up really well. Give it a second to evaporate while we pull the cover off our foam tape. Take it right down and get it mounted in to position. Wiggle it around for a few seconds and make sure it gets a good, firm hold. We can, also, take care of our ground wire while we're here. We want to find an area that has good sturdy steel but something that's not exposed to the outside, so we're not going to drill from the inside of the car right outside. We've got an area right here that's nice and flat and out of the way, so let's give that a mark. Then, I'm going to use the provided self-tapping screw to start a hole. With the hole started, we'll add our ring terminal on and re-secure it. Now, that we've got that situated, we've got a nice grommet right here on the back side, kind of centered. We're going to use this to get our 12-volt wire in to our car and, also, get our 4-pole wire out of our car. We'll take a screwdriver and pop that out. If you reach out from the bottom, it's easy access. We'll take a little bit of slack off of our 12-volt wire, place it right up here underneath the bumper and grab it with our other hand where we can pull it right through. Let's strip the end off, slide that in to the yellow butt connector and then, crimp it down. Now, we'll get our 4-pole wire routed over the direction we want it to go. Stretch it out. If we pull the cap off, we should be able to pass it right through and pull it on out, same direction our 12-volt wire went. We're going to trim a little section out of the grommet that we'll use for our 4-pole and our 12-volt wire to pass through. Then, we make one slit to the outside to place them in. Fit it around our wire first. Then, we can plug it right back in the hole. Now, with a little bit of silicon around those wires, we'll have it all sealed up. We'll use a zip tie to quickly bundle up any extra 4-pole wire. You may need all of it out there, just depending on where the connector's at on your trailer. You may need just a portion. We can, also, leave this just bundled up here in the back of the trunk, if we wanted to. We didn't have to pass it through that grommet. It just gives it a nice look. If we had it bundled up here in the trunk, we just bring it up over the edge and then, the seal that's right here on the edge prevents it from causing any kind of damage and we can just let it hang out. We've got those taken care of. Let's move on and get our passenger side connection made here. It's the red and green wire. We bring it across the back. It's going to go behind the threshold like our 12-volt wire inaudible 00:08:10. Then, we'll need to remove 3 fasteners here that are going to be in the same location as the one's on the driver side. We'll pull that back. Our passenger plug will be right there. We'll squeeze our tabs in like before. Wiggle it out to separate it. Bring in our other side and get them plugged in. Connection's made. Tuck it back out of the way and we can bring our trunk liner back around and get it repositioned. If we pull up on that rubber gasket, going all the way around, that edge will go back in. We'll get our driver's side put back together. We'll, also, get our threshold put back in to place. Line up our top here first, get it pushed down and then, push in on the front. Nice and secure. Check our wires, or course. We want to make sure that they're not being force out or pushed any weird way; not getting pinched. Everything looks nice. We'll put our trunk lining back in and we'll be done in the back of the car. Now, our 4-pole wire, we're going to tuck that up and out of the way. Our 12-volt wire, we're going to start unwrapping it. Now, that we've got it stretched out, I'm going to add it to a piece of airline tubing that we've got lying around the shop. You could use a coat hanger, a stiff piece of wire, whatever you have available. You want it to be kind of stiffer then the wire we're trying to work out. It's going to act as a guide, so we can get this right where we want it. We're going to start working our way to the front. We're going to avoid any sources of heat, any pinch points, any areas that we might have any kind of damage done to our wire. Shove it up over my 4-pole real quick. We'll run right along our heat shield here. Come out here. Now, we'll hop right over the heat shield here and we can get over, closer to our brake lines and follow those up towards the front of the vehicle. We'll pull down our cover here. Use a 10 millimeter socket. Just going to back these out. It's going to help us get a little easier passage running up towards the front. Just tuck that in the full length there. Pull out the slack in the front and we'll put those nuts back on. Cross right over here. Start guiding our fish wire out. We'll have to reach out here beside our exhaust. We want to guide it up towards where our brake lines are running. It's going to be up in that general area of our battery where we'll make our connection. Now, we can go up there and find our pole wire. The master cylinder's located here. We we're guiding our pole wire to that direction. We want to reach in down in that area. See if we can find it. There it is. Pull our wire on up through here. Pull out all the slack that we've got. This, we're going to run right down beside the battery. Tuck it down there nice and low. Then, we're going to make a quick loop and come right up here to our panel. Let me show you. See, we have our positive from the battery coming in right there. That'll make a great attachment point for us. We're going to make one coil and our wire, snip it off, strip the end of it and add on one of the provided butt connectors. We'll bring in our yellow fuse holder. We're going to cut this about 60/40, so about 4:00 position down here. We'll strip both ends of that off. Now, the short end we're going add a ring terminal to. The long end gets connected to the butt connector we added to the end of our black wire. Then, well come in, loosen up our positive terminal, add our ring terminal on to the post, push that down. We'll put that right back on top. A nice solid connection there. The cap will come back over. Tidy up our wires here a little bit. Use a few of our zip ties. Put a fuse on our fuse holder. Cap it off and we'll go check the system. Make sure it's working properly. Testing our wires is a pretty simple process. We're going take a standard test light. We'll hook the ground clamp up to our ground wire. That'll test that for us. Then, we'll have our partner turn on the standard running lights, or the headlights. That should give us a constant signal from the brown wire. Next thing we'll have him do, is turn on the driver side blinker. That should give us a flashing signal from the yellow wire. Next thing we'll have him do is turn on the passenger side blinker. That'll give us a flashing signal from the green wire. Finally, we'll have him hit the brakes. There we should have a steady signal from the green wire and from the yellow wire. With everything working properly, we're ready to hook up to our trailer and we can get heading down the road. That's going to complete today's installation of the Tow Ready T-One Vehicle Wiring Harness with the 4-pole flat trailer connector. Part number 118572. On our 2011 Volkswagen Jetta.


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Info for this part was:

Test Fit:
Joe V
Installed by:
Jeff D
Video by:
Andrew L
Video Edited:
Kathleen M
Test Fit:
Randy B
Video Edited:
Chris R

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