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Trailer Wiring Harness Installation - 2008 Ford Fusion

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How to Install a Trailer Wiring Harness on a 2008 Ford Fusion


Today on our 2008 Ford Fusion, we're going to install the Towready T1 Vehicle Wiring Harness with Four Pull Flat Trailer Connector, part number 118422. To start our install we'll go ahead and open up our trunk. First we're going to go ahead, raise up the trunk liner here and just tuck it up here out of the way so we can get access to the side panels here and where our wiring is. So let's take this, you fold it up a little bit, it'll tuck it up out of the way. Now we need to go ahead and remove our threshold, there's a few push fasteners here, there's one here, there's two here on the lower part, and one over here on the side, so we'll go ahead and take those out with a trim panel remover tool or if you have a large flat blade screwdriver you can get underneath it and pop that out, so we're going to remove those and then we can move our threshold out of place. You just got to work them out, sometimes they pop out, sometimes they put up a little bit of a fight but they will come out if you just work back and forth. Just go ahead and set those aside, and before you can get your threshold free there are two more push fasteners here, right here, and on the other side, they do kind of blend in, you'll be able to see them, trim panel tool there and pop it free. And then we take our trim panel tool here, get it underneath the edge of our threshold and pop it free, and once you get all of this free, as you can see there's just these tabs here that clip in to the body, once you get it popped free you can just take your threshold and set it out of the way.

Now once you have your threshold out of the way you can see that it loosens up the carpet, and we just take it here and fold it back out of the way, and our connectors here for our taillights that we need to T in to are right here, so we can go ahead and grab our wiring harness and start make our connections. We'll go ahead and bring in our T-Wiring harness, for the driver's side you'll be using the one with the brown and the yellow wire along with the white wires, that'll T in here to the taillight, so we need to go ahead and unplug our taillight connector, see, just simply push right here on it and you're able to pull it out, then we can add our new connectors right in to this.Now going to the passenger side, again, just fold back our carpet a little bit, and slowly gain access here to our connector. Now we can go ahead and run our connector here with the green and the white wire over to our passenger side and make those connections. Next we need to go ahead and take the white wire that's coming out of our module, which is the ground, it has the ring terminal on it, we're going to go ahead and use this factory ground here in the trunk pan, we'll go ahead and take an 8 millimeter socket and remove that. We'll take our white wire with the ring terminal, install it here and just reinstall the bolt. Now we need to go ahead and mount our module box, we're just going to go ahead and use the double sided tape that's with our install kit, and it's going to go right here to the bare sheet metal, we'll go ahead on the back side of our box and install our tape, peel off the other side and put it in to place. Now the four pull wiring that comes off our module will stay in the trunk when not in use, we''re just going to go ahead and set that to the side, and we're going to start zip tying up our wires, first we're going to take the excess green wire here, bundle it up, and we're going to zip tie it here to the factory wiring harness that's running across to the passenger's side.

Now the wiring kit does come with some zip ties but it is always a good idea to get some extras when you're doing wiring work. Go ahead and bundle up a little bit of this wire here on the driver's side and do the same thing, just put a zip tie here to hold it tight. Now that we have that secure, we can go ahead and fold our carpet back. Next we're going to go ahead and take the black wire that comes with our wiring kit here use a butt connector that also comes with it and connect it to the red wire. Eventually that black wire will get ran outside and eventually in to the engine compartment and then hook it in to a 12 volt source. First I'll go ahead and strip back the black wire, and add our butt connector, crimp it now nice and good, and now we can go ahead and attach it to the red wire coming from our module box.

Now go ahead and just take some electrical tape and tape up that connection point just to protect it from any dirt, debris, or moisture. Now to run our power wire outside, we're going to go ahead and take a drill bit there's a grommet right here, and we're just going to poke a hole in it and we'll be able to run our wire to the outside of our vehicle, just be careful when poking through this as there is the fender on the other side, so you want to do it very gently, or you can go ahead and take a very sharp utility knife and try to cut a slit in it to run it out. Now I'm going to go ahead and take the other end of our power wire here, run it through the hole in to the outside of the vehicle. Once you get it ran outside enough, you'll be able to go on the outside, reach underneath the car and pull the rest of it out. And just pull it from the outside, you may have to feed it in a little bit on the inside just to get it to go. Now as you can see, nice straight line going to the outside for our power wire, and we can just go ahead and zip tie right here to keep it in place on the inside, trim off the zip tie, and fold our carpet back in place.

Then we reinstall our push fasteners that we removed. The nice thing about this wiring harness is since it is on the inside when you're not using it, you can just store it here by your spare tire, and cover it up with your trunk cover. Now we'll go ahead and go underneath our vehicle and run our power wire up towards the engine compartment. When you run your power wire you want to stay away from any moving components such as the suspension or any excessive heat such as the exhaust. Right here, we went ahead and put some wire loom on it just to protect it against this sharp edge, when we ran it here over the subframe in the back of the vehicle, up over the suspension, to keep it away from it. We went ahead and ran it along the side of the fuel tank here, following the brake lines and fuel lines that run here along the vehicle, using a couple zip ties, we we're able to come across and then follow those lines all the way towards the front of the vehicle. I just fed the wire here up over the holders, down here, and went straight up, right over the fire wall and in to the engine compartment, went ahead and used a pull wire here to pull our wire up here from the bottom to the top right along the fire wall. Our black power wire here, right along the fire wall here right behind the battery, went ahead and zip tied it right here to the ground cable that's just right here and ran it over to our battery, and we're going to eventually hook in here to the battery on a 12 volt stud. We're going to go ahead and measure out our wire, we are putting an inline fuse on this wire so go ahead and measure it out, trim our wire back and strip it. Now we'll bring in our fuse holder, see it makes a loop so all you have to do is go ahead, cut it in half, and strip back both sides. One side will get connected to the black wire and the other side will get a ring terminal, that ring terminal will go on the 12 volt stud here on the battery. Crimp our ring terminal down on to it, and then put a butt connector on the other side. Now we'll go ahead, get that here on our black power wire, and crimp it down. Now we can go ahead, take a socket, and undo the nut here on our stud, and install our ring terminal, use a 10 millimeter socket, install our ring terminal and reinstall the nut, put our terminal cover back on, and then we install a fuse that comes with our wiring kit, just go to the fuse holder, push that in there and install the cap, then I'm going to take a zip tie here, just tuck our wire in, and zip tie it out of the way. Now to use your four flat wire, all you have to do is open up your trunk, raise up the cover here in the rear, bring your wiring outside, run it to the outside toward your hitch, and close your trunk. The weather stripping here will protect your wires here so they won't get damaged, you just want to make sure you stay away from the latch here in the middle, and now you can run your new wiring to your trailer and hook up. Now we'll go ahead and test the wiring, we'll go ahead and take the ground for our test light here and put it on the open stud, that's the ground for our four flat. We'll test the brown wire which is the running light circuit, see we get a constant signal, go ahead and turn on the driver's side turn, that's the yellow wire, test the green wire which is the passenger turn signal, and then we'll hit the brakes and you'll get a constant signal on the yellow and the green wire, and now with everything working we can go and hook up our trailer and hit the road. That'll do it for our install to tail ready T-1 Vehicle Wiring Harness with Four Pull Flat Trailer Connector, part number 118422, on our 2008 Ford Fusion. .


Info for this part was:

Employee Joe V
Test Fit:
Joe V
Employee Nicholas E
Test Fit:
Nicholas E
Employee Alan C
Test Fit:
Alan C
Employee Zack K
Video Edited:
Zack K
Employee Andrew K
Video Edited:
Andrew K
Employee Joshua S
Video Edited:
Joshua S
Employee Chris R
Video Edited:
Chris R
Employee Jeff D
Installed by:
Jeff D

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