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Tekonsha T-One Vehicle Wiring Harness Installation - 2016 Mercedes-Benz Sprinter 3500

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How to Install the Tekonsha T-One Vehicle Wiring Harness on a 2016 Mercedes-Benz Sprinter 3500


Today on our 2016 Mercedes Benz Sprinter 3500, we're going to be taking a look at and also showing you how to install the Tekonsha T-One Vehicle Wiring Harness with the 4-Pole Flat Trailer Connector. The part number is 118649. Now, this is what our kit is going to look like. This kit is going to offer us a direct plugin solution to get a working 4-pole trailer connector at the rear of our vehicle. The 4-pole connector is going to give you right turn and brake, it's going to give you left turn and brake, and it's going to give you your running light signal, also a ground to make sure all of our lights work. Now, the way this system works is we have a module box. This is going to take signal from behind the driver's side tail light and from behind the passenger's side tail light housing, and it converts it into a usable signal for our trailer.

This is also going to act as a safeguard. This is going to allow us to separate our vehicle system from our trailer system, so any shorts or anything like that in your trailer aren't going to affect our vehicle system. Another great feature of the box is the power wire here, which we'll connect using the extra wire and fuse holder, is going to be a standalone power source for the converter, so we won't be using any of the power from behind our tail lights. We're not going to be putting any excess drain on the vehicle system. It's going to have its own power source to send power out to our trailer. The white wire is going to act as our ground, and you'll see they've supplied us with plenty of stuff. There's plenty of zip ties here to get our install done.

They provided heat shrink butt connectors. That way it's going to give us superior moisture resistance. We've got our ring terminal to connect to our battery or positive stud. Going to have the self tapping screw there. That's going to be for our ground wire.

Then, of course, we've got our instructions here, our fuse and fuse holder, and then even some double sided foam tape, if that's what we decide to use to mount the box. Now, the area we need to get to is going to be right behind the tail lights. There's a few openings here, and in the second opening up from the bottom, if you look inside there, you're going to see a long, rectangular shaped black plug. You can see it right in this location. There's going to be a locking tab right on that bottom side and on the top side. It's just a little tiny locking tab.

You want to press up or down on those respectively and then pull the wiring out. See, that's what our plug will look like when we pull it out. It's going to plug directly in to our T connector harness. Plug it in until you hear that click, and you should be able to pull on it without it separating. The other end is going to plug in where we just removed that. Now, we're going to take our module light box, and we'll get that zip tied off right here. The customer has requested that we get his 4-pole outside of the vehicle, so there's a small access point right here, which goes into a slot in the frame. Now, with all of this piping and AC and wiring that's here, it's going to make ours pretty difficult to do. If you do choose to take yours outside, you should be able to go in there and then right out of a cap that's on the frame rail. Here you can see where that hole comes out underneath here. What we're going to do is just . you could probably use a stiff piece of wire. You might even just reach in there and feel the hole in the backside, but you can see all this extra we've got here. We're going to use a pull wire to go up in there. On the bottom of that pull, we're going to attach our 12 volt wire. This will allow us to pull it up into our box, and we won't have to try to bring the whole length of wire down out of the vehicle. We'll just use that to pull our 12 volt wire up through here, remove it from that pull wire, and then we'll make our connection with the wire coming out of our black converter box. Now, we'll use one of our heat shrink butt connectors to make our connection here. Let's strip that wire on our converter back just a little bit. This is going to be inside the car, so it's not imperative here, but in the front, you want to get this shrunk down. Now, the heat gun is usually the best solution because you won't have to worry about overheating them, but you can also use a lighter or a mini-torch, and just be careful not to discolor the butt connector. When it's shrunk down all the way, you're going to see the wire kind of look like it magnifies, and then there's a little clear gel that comes out of the end. Now, I'm going to pass my 4-pole down through. You can see how that cover comes down and offers dust protection for us. This is eventually going to be becoming a 7-pole setup, so we're eventually going to be cutting the end off of this wire. I'm going to leave it on there now so we can test it, but in order for me to pass it through this area over here, I am going to need to remove this cover. Now, if you're not going to be doing what we do here in passing in and out, the black wire is the only wire you need to run outside of the vehicle. This can be stored in the back or that, there's a little cubby hole here or here, usually. You just pull it out over your sill here when you want to use it, and you'll see that little bit of cushioning there protects it, and just pull out whatever length you need and connect it to your trailer. This is kind of a custom installation in that we are going to be taking our wiring outside of the vehicle. I'm going to try to follow the same path as that power wire there. We'll just pull down our slack there. Now, the 4-pole will run over this way, maybe use a couple wire loom there, over towards the middle of our hitch area. Our 12 volt power wire, that's going to run up to the front of the vehicle. Now, you'll have a few spots in the frame, you can use the loom clamps or zip ties. In our case, I'm definitely going to run up with this big piece of wire loom here because it's already there. It's going to be easy to do. Then we can run that up to the front of our vehicle. Now with our connections made there, ran outside, we'll get this zip tied off. Our red and green wire, we'll just stretch it out. We're going to be running it across this rear sill plate here in just a few minutes. That will pretty much wrap it up in this side here, with the exception of grounding our wire out here. Get that done. Now, you'll use a quarter inch bit driver to secure it. It's a self tapping screw, so it's going to create it's own hole. You just want to make sure that's secure enough to where you can't move that, or wiggle that ring terminal. Just like that. Now, any panels or anything you've removed on this side, you can get them put back in, and we'll run our wire over to the passenger's side. Now we need to pull up the push fasteners that run across the rear scuff panel here. That's going to allow us to run our wire underneath. See, there's just a little notch in them, you'll pry up with a screwdriver, and just remove them completely. Just like that. Now, we'll just extend our red and green wire. Let's get this over there to the passenger's side and get it hooked up. We're going to have some extra wire here. There's a trim panel that runs across here. Again, this is a limousine conversion that's been done. If this piece of wood and this carpeting wasn't fastened down on top of this rear scuff panel, I'm just going to pull these fasteners out, remove that scuff panel, and we can run our wire underneath there, or you can also opt to go up around the top and come back down the other side. Once we have our wiring over this direction, we're going to separate our connector. It's going to be identical to the driver's side connector and located in the exact same place, of course, on the passenger's side. Now, we'll zip tie this side off, keep it, again, from moving around. I'm also going to be using this space over here to bundle up my excess wire. Now, the battery for the Srinter is located just forward of the driver's seat here, underneath the floor. You'll notice here on the back side, we've got a red cover. There's a 12 volt hot lead right underneath here. Just going to kind of pull straight back on that cover and rotate it out of the way, and you'll see that stud right here. Now, this is going to be a good place to connect. It's going to keep our fuse holder kind of up here and out of the way, so we'll back that off and connect our ring terminal. We're going to be putting a fuse holder in place here, so we'll need to strip off each of the ends of that. You see, you kind of cut it offset, a little bit, about 4:00 position. We'll just strip all these back. Now we'll crimp that heat shrink butt connector on the longer side of the fuse holder and connect that to our 12 volt wire. It's okay to have a little bit of extra wire here. We can bundle that up, and if anything ever needs to change, it'll allow us some flexibility in there. On the other side, we're going to have it on a ring terminal. You'll see the ring terminal provided will be the appropriate size to go over our stud there. Just place that on and get it crimped, as well. Alright, now we can get our butt connector shrink down. Now we'll use our 13, and we'll want to take the nut off our stud here. Place our ring terminal up and on. Try to have that run about the same angle as the cable there, then you can replace the nut. Now, the cover is going to have a small notch out right here. That's what slid over the old post as it came out. We're going to enlarge that just slightly to also accommodate the ring terminal there. Now we can take our fuse, and we're going to place that in our fuse holder, place our cover on it, and now we just need to get our wiring secured off. We'll go right to that cable. That way, if they ever take that battery cable off, this will come with it, rather than being separate. Now, let's get our 4-pole wire ran over towards the center of the hitch. That's where it's going to be attached. Now, as you come by your hook here on the spare tire rack, you definitely want to stay inside of that. We're going to use these clip points all the way down to keep our wiring secured above that. Now, from this point, you've got options with what you want to do with your wiring. Some people will just bring it around and then use that protective cover to go around the safety chain connection point, and it'll stay there for you. There's an attachment tab here for a bracket, or if you don't have this, you could use part number 181410, which is a universal short bracket, and create an attachment point that would stick off there. Then on this bracket and that bracket, you'll have pre-drilled holes, and you can use part number 18144, which would be a 4-pole bracket, and you can have it where it would just kind of sit right there, more permanently attached. Alright, now to test out our wiring, let's turn on those running lights. Our left blinker, our right blinker, and our brakes. That's going to complete our installation of the Tekonsha T-One Vehicle Wiring Harness with the 4-Pole Flat Trailer Connector, part number 118649 on our 2016 Mercedes Sprinter 3500.


Info for this part was:

Employee Joe V
Test Fit:
Joe V
Employee Randy B
Test Fit:
Randy B
Employee Jeff D
Installed by:
Jeff D
Employee Jacob T
Video Edited:
Jacob T
Employee Kathleen M
Video by:
Kathleen M
Employee Chris R
Video by:
Chris R

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