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Trailer Wiring Harness Installation - 2007 Volkwagen Jetta

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How to Install a Trailer Wiring Harness on a 2007 Volkswagen Jetta


Today on our 2007 Volkswagen Jetta, we'll be installing the tow-ready T One vehicle wiring harness with 4-pole connector, part number 118531. To begin our install, we'll first go ahead and open up the rear cargo door. Then we'll remove the spare tire cover and rear threshold. On this application, the rear threshold is missing some of the fasteners to secure it, so we can just go ahead and pull up on it, releasing the fasteners from underneath. Then we'll set aside and move to the rear quarter panels, where we'll need to remove the rear carpeting to gain access to the rear taillight wiring. By opening the access door, we can see that the wiring is behind the taillight, so now we'll go ahead and remove the fasteners.

On most applications, there will be a total of three fasteners on each side, two push pin fasteners, the center of the push pin fastener will be screwed out and then removed, and one plastic cap nut. Now with our fasteners removed here on the passenger side, we'll go ahead and pull the carpeting away as we can see the wiring that runs to the back of the taillight housing. Now we'll go ahead and repeat the same process on the driver's side. Now with both sides exposed, we can go ahead and take the new wiring harness and plug in line with the manufacturer's wiring by removing the connector behind the taillight assembly. To remove the connector, we'll pull back on the spring loaded locking tab, remove the connector from the socket, and then plug it into the yellow and brown wire connector for our new tow-ready wiring harness.

Then we'll take the other end of our T connector and plug it back into the taillight assembly. Next, we'll take the green wire connector, follow the manufacturer's wiring around over to the passenger side, where we'll repeat the same process. Next, we'll go ahead and take the gray connector portion of our wiring harness and the black converter box supplied with our install kit, and plug the converter box into the harness. Then we'll take our converter box and mount it. To mount it, we're looking for a clean, flat surface to adhere it to, preferably sheet metal.

Here on the driver's side is a perfect location. Next, we'll take the white wire with the preattached ring terminal and secure it to the body of the vehicle for our ground for our new wiring harness. Using a self-tapping screw, we'll go ahead and mount it here below the taillight housing assembly where the sheet metal bubbles up. Now we'll take the black wire with the yellow bud connector preattached, which will be the power wire for our converter box, take the long length of wire supplied with our instal kit, strip back one end, and secure it to the yellow bud connector. Then we'll go ahead and take some black electric tape and wrap up this connection point to help keep out any dirt, dust, debris, or moisture.

Next, we'll need to take the power wire, run it outside the vehicle, and up to the engine compartment. To run it outside the vehicle, we'll run it over to the passenger side, following the green wire we ran earlier, and drill a hole for the plastic grommet. Then we'll run the wire underneath the vehicle and up to the engine compartment. To assist us in routing our wire underneath, we're going to go ahead and lower one of the underbody trim panels. Keep in mind when routing your wire to stay away from moving components, the steering or suspension, or excessive heat such as the exhaust. Once we've routed the wire underneath there, we can go ahead and reinstall the underbody trim panel and cut off the excess on the zip ties to clean up our install look. Now with everything routed and secured in the rear cargo area, we can go ahead and reinstall the interior trim components. Once we get to the engine compartment, we'll run to the top of the engine bay and over to the fuse box, where we can get battery power. We'll go ahead and cut to length and strip back the end of our power wire that we just ran. Then we'll go ahead and prepare the fuse holder. The fuse holder will be cut in half. Strip back both ends. Add a yellow bud connector to one side, and a yellow ring terminal to the other. Then we'll go ahead and secure our black power wire to the yellow bud connector, wrapping up this connection point with some black electrical tape. Here we'll remove the nut on the power supply post, install the ring terminal, and then re-secure the nut. Then we'll go ahead and install the fuse in the fuse holder and replace the cap. Then we'll go ahead and reinstall the fuse box cover, locking it back down. Next, we'll go ahead and show you how to use your new 4-pole connector. With it stored in the rear cargo area, we'll open up the rear cargo door and the spare tire cover. We'll route the 4-pole connector down to the hitch or accessory, being careful to stay away from the latch, because pinching the wire off in the latch can harm it. However, the weather stripping is thick enough that we can simply close the rear cargo door on it. Then once we're finished using the 4-pole connector, we'll simply roll it up and store it down with the spare tire. And that does it for our install of the tow-ready T One vehicle wiring harness with 4-pole connector, part number 118531, on our 2007 Volkswagen Jetta.