Trailer Wiring Harness Installation - 2004 Mazda 3

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How to Install a Trailer Wiring Harness on a 2004 Mazda 3


Today, on our 2004 Mazda3 five door, we're going to be installing to Tow Ready T-One vehicle wiring harness before pole flat trailer connector, part number 118420. Now, to begin with, we are going to need to open up the rear hatch of the vehicle. We'll then need to remove this center threshold piece, here. Now, in order to do that, we need to lift up a couple of item here so we can pull the center threshold piece out. Go ahead and set this piece out for now too to give ourself a little bit more working room. Now, in order to remove this center threshold piece, there's a push fastener, here, that you'll need to remove, looks something like that, and there's one right over here on this side as well. With our two push fasteners removed, go ahead and gently pull up on the center section, releasing the tabs underneath.

So, we'll go ahead and set the whole center threshold piece off to the side for now. Now, with our center threshold piece removed, we'll have another push fastener right here. Just take a screwdriver and work it in underneath the edge. The center will pop out and you can remove the whole tab. We'll also need to remove this tie down hook right here. Simply lift the cover up, we'll need to remove the bolt that's underneath it.

Just using a ten millimeter socket to remove the bolt. Go ahead and set the whole tie down hook aside. It'll then allow you to peel this piece back enough that you can slide your wiring up underneath it. Now, over here, on the driver's side, you can turn the handle and gain access into the wiring by removing the door and our wiring will be right up underneath here where we tie in with the lights. Now, in order to pull this cover back a little bit more, we are going to go ahead and remove this cover right here at the back of the plastic section and inside there there is a little Phillips head screw that we'll remove. Then go ahead and slide the carpeted section out. This will allow us room to work the wiring in behind it. Let's go ahead and go over what the wiring looks like we'll be tying in with.

So, over here on the driver's side, we'll be tying in the wiring harness or the T connection that has the brown and the red wire as part of it as well as the T connector that has the yellow wires in it. Next, we are going to need to undo the wiring from the backside of the taillight. To do that, simply squeeze in on the locking tab and gently pull outward. Go ahead and disconnect the other one as well. Next, we'll go ahead and take our wiring harness, feed it in behind the carpeting, where we'll then go ahead and connect our T connectors in line. So, we'll take the larger one, connect it to the red and brown connection point making sure that we hear it fully lock or engage with the locking tabs. Go ahead and repeat the process on the yellow wire.

We'll then take the other half of the T connector and plug it into the backside of the taillight assembly. Next, we're going to go ahead and take a paper towel with a little bit of rubbing alcohol on it, we're going to clean this surface right here, get any dirt, oil or any other debris off of it that way our two sided tape on the backside of our converter box will stick to it. We'll go ahead and mount our box right in that area. Peel the covering off the two sided tape, here, on the back, go ahead and attach the box. Next, we have our white wire with the ring terminal on it. We'll go ahead and attach that right here to the metal as well. This will be our ground screw. We'll be using the self tapping screw that comes with the kit in order to do that. Next, we are going to come over here to the passenger side. We are going to need to repeat the same process removing the fastener and the tie down hook. Now, on this side, we've got the carpet released, we'll go ahead and squeeze this center section out here. Now, we are ready to take our green wire T connector, routed over from the driver's side, where we'll go underneath the carpet pulling it up into our opening, here. Now, on this side, we'll only need to remove this connector right here, the one that has just two wires coming out of it. So, we'll go ahead and squeeze the locking tab and gently pull outward. So, you'll be taking out this one, right here. Go ahead and add our T connection in, go ahead and plug it back into the taillight assembly. Now that we have all of our connection made, we can go ahead and put our interior panels back together on both the passenger as well as the driver's side. Now, we've also made sure that the four flat wiring, here, is brought out to the center section. We'll just go ahead and just, kind of, set it over here for now so that it's out of the way as well as our green wire that routes over that I'll just, kind of, store down here in this lower storage area then go ahead and put out center threshold piece back in place. You will need to work the rubber weather stripping back up to the top side of it. To do that, you just simply take your fingers and gently slide them underneath and work the rubber molding up over the top of the threshold piece. You can also use a trim panel removal tool or a plastic trim panel piece to help you slide the weather stripping back up into position as well. Then, go ahead and put our two push fasteners back in. Then, go ahead and put out tray back into place and then go ahead and store your four flat wiring, here, in the tray compartment area when not in use. Then, go ahead and slide our final piece back down into position. When you're ready to use your four flat wiring, you'll simply lift up the cover, here, pull the wiring out, route it to the center of the vehicle, just to the side of your center latch area. You then simply close the rear hatch on the wiring and the weather stripping will push in allowing the wiring to be through the center of the hatch area when the door is closed. Now, we are going to go ahead and take our test to make sure that our four flat wiring is working correctly. Take the ground on our test light and connect it to the open prong, which is the white wire in the ground. We'll then turn our running lights on where we'll touch the brown wire, the left turn we'll touch the yellow wire, right turn we'll touch the green wire and the brights we'll touch the green and the yellow. As you can see here, all of our functions are working just fine. When you are done with your four flat, simply put the rubber cup back onto the four flat and then you can store it in the trunk compartment area and that will do it for our installation of the Tow Ready T-One vehicle wiring harness, part number 118420 on our 2004 Mazda3 five door. .


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Info for this part was:

Test Fit:
Joe V
Test Fit:
Nicholas E
Test Fit:
Shane T
Test Fit:
Hayden R
Test Fit:
Shane H
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Zack K
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Joshua S
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Jacob T
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Andrew L
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Andrew K
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Kathleen M
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