Trailer Wiring Harness Installation - 2017 Volkswagen Golf
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How to Install a Trailer Wiring Harness on a 2017 Volkswagen Golf
Today in our 2017 Volkswagen Golf we'll be having a look at and installing the Curt Powered Tail Light Converter with Four-pole Flat Trailer Connector, part number C59236. Here's what our wiring looks like installed. Now our wiring is designed to be stored inside our vehicle when it's not in use. One of the reasons you're gonna want this converter style that you have to splice in over other options available on the market is many Volkswagen Golf's on the market use poles with modulated wiring in their tail light systems, which are not compatible with many plug-and-play options. Now we'll show you how to get it installed. To begin our install we'll open our rear hatch. Now we'll take out all of our floor coverings. And to make it easier to see, we'll take out our cargo cover here.
Now the center trim piece here, we're going to remove this by pulling up on it. Now we have a torque screw down here in this recessed pocket that we're gonna need to remove. We have another one up here that's in the hinge area for our luggage cover. Now this pocket over here, we'll just grab this and pull it on up. We can grab our interior panel now and start pulling it away.
We don't need to take it all the way off, just enough so we can pull the carpet back behind it. We have two plastic retainers that hold our carpet into place. Use a trim panel tool, and we'll pop these out. With our driver side panels loose we have access to our tail light connector, so we'll repeat the same process on the passenger side. So we need to remove our tail light bulb here partially. In order to do that there's a black tab right here.
We'll press on it and pull back. We won't be able to remove it all the way, but we'll be able to rotate it now to gain access to the lock tab for our connector. So we'll slide this red tab back and press on this black tab here and pull apart. Now that we have our panels apart, you can see I've already made our connections here, but I'm going to explain to you how we came across the wires that we we're gonna use to use our connections. We're only splicing in one wire on each side. The one that we're working with on the driver side is this black and red wire.
This is where we tied in our yellow wire for our left turn signal and left brake light. Now the the reason we're only doing one connection on each side of the vehicle is because this vehicle has what is called a pulse width modulated system. What that basically means is you're not seeing full 12 volts typically. Everything is switched on via low voltage input from our computer, around five volts. I'll explain how this works. I got the positive lead of my multimeter. You're gonna need a quality multimeter for this. I'm gonna go to the back side of my tail light connector and back probing the red and black wire. You back probe something, you don't damage the connector, so you still have good electrical connection. The negative lead of my multimeter, I'm just gonna ground out on our chassis here. Now if we look at my multimeter, you can see I'm registering half a volt. Now this is because I have my headlights turned on right now. So what this is doing is it's bypassing some of the power from the tail light circuit over to our brake light and turn signal circuit giving us a half volt, which isn't enough to turn your lights on, but it is enough to confuse your module that controls your 4-pole flat convertor. So I'm gonna turn my turn signal on now and we'll test for more voltage. Still back probing the red and black wire and with the turn signal on you can see it's going to five volts whenever it flashes. So we know that's our turn signal circuit. Now we'll turn our brake on and test it again. We're reading basically a full 12 volts, which is full power output for the light and that's what we're looking for here. Now we'll repeat the same process for the passenger side to find out which one is our turn signal and our brake light wire. When we did that on the passenger side, we found that that is the purple and black wire. So we made our connection with our green wire here for our turn signal for the passenger side. Now because we only need to have the two connections to our vehicle's wiring and this is a combined multiplex system, our brown wire here, which is typically for our tail light circuit, and our red wire here, which is for our stop light circuit, we combine those with the white wire, which is our ground wire. We use a heat shrink butt connector for all of our connections. We have these available on our website. And our ground wire we grounded behind a 10 mm nut, which is a factory ground point right here. I stuck our double-sided tape to the back side of our convertor box here. Now I'm gonna stick this to a flat surface nice and firm. Right where I'm pointing we have a grommet. This is behind our carpet on the driver side. We'll just grab this and pull it on out. We're gonna make a modification to it. Now we'll take the grommet. This is the bottom of it that faces the bottom of the car. Here's the top of it. I'm gonna go through the bottom with a drill bit here. Now we'll take the other end of our black wire and we'll pass it through that hole we just drilled. Now we'll stick the end of our black wire through the hole where the grommet was and we'll feed it all the way down until the grommet is back in place. We'll push the grommet back in. With the black wire coming off our module we combine with the black wire with our kit with the butt connector. I went ahead and routed our power wire from where it leaves our grommet here towards the front of the vehicle, making sure we avoided any moving parts or sources of heat. I followed along the sub-frame connector here, zip tied to it, goes over the rest of our sub-frame, comes out over our sub-frame here, have it zip tied to what could be an exhaust hanger on some vehicles. Ours is a GTI module, so the exhaust may or may not be different than your vehicle. I go through this slot here in the lower control arm. It's right by the pivot point so it doesn't matter. This won't flex very much. I have it zip tied to the few cable in a few spots. Then it goes underneath our plastic shield here. I have it zip tied to the end of it here, so it'll keep it in place. And it comes out right here. This is our pole wire, which I dropped down from our engine compartment. I have our wire taped to it, so we can pull it up into our engine bay right now. Here's our pole wire and we'll pull it on up. We have our power wire zipped up here to our battery cables, just to help keep it from falling. Now we'll lift open our flap here that covers our battery. I'll just tuck it down here out of the way for right now. This post here is our positive post. That's where we need to make our connection. We'll cut off our excess wire right here and we'll strip back some insulation from the wire, drop on our butt connector, and we'll crimp on down. Take our fuse holder here, strip off some insulation, stick that in the other end of the butt connector. On this other side of our fuse holder, we'll strip off some insulation, stick on our ring terminal. Now we just need to make our connection to the positive terminal by removing that 10 mm nut. We'll slide our ring terminal on over that stud and re-secure our nut. Now we'll take our provided 10-amp fuse and install it into our fuse holder and close our dust cover on up. With all of our connections made in the back here we can reinstall our panels. Make sure our weather stripping stays on top of all of our panels like it's supposed to. We're using a 4-pole flat trailer tester to test our wiring. We have these available on our website as part number I26 if you'd like to purchase one. We'll start by turning on our headlights. As you can see our tail light and running light function on our trailer would be working. Now we'll do a left turn signal. That's working as well. Followed by a right turn signal. That's working too. Now we'll step on the brakes. That's working as well too. We'll combine our brakes with our turn signals at the same time to make sure they operate properly. Looks good there on that side and good on that side. Now we've verified all of our functions are working properly. That completes our look at and installation of the Curt Powered Tail Light Converter with Four-pole Flat Trailer Connector, part number C59236 on our 2017 Volkswagen Golf.
Louis O.
8/22/2020
Important question about tail lights: The video mentions one connection each side that controls both brake and turn. But it doesn't mention tail lights. Does this one connection each side also control tail lights (via pulse width modulation)?
Jon G.
8/31/2020
If you have a 2-wire or 3-wire system them the brown wire will carry your tail lights. If you have the PWM-ST or PWM-STT vehicle wiring then you'll ground the brown wire and use the red or green/yellow wires accordingly. The instructions point this out on page 3.
Bruce
6/16/2020
does this video apply to the 2015 VW Golf....the wires on mine are the same colours and there appears to only be one wire supplying both brake and turn lamps? Also why do you ground the tail light wire, there is a wire supplying separate power for the tail light?
Chris R.
6/21/2020
I can't be certain that the wire colors are the same on your 2015 VW Golf because manufacturers tend to switch these up without warning. Your best bet will be to actually test them for function before making any connections.
Bruce
6/21/2020
@ChrisR
Thank you Chris I really appreciate you getting back to me. The color of the wire is not the actual concern...it is more that there is a shared wire supplying the brake and turn lights. The regular instructions suggest that I should have a separate wire for each, and that I should connect to each with the appropriate wires from the converter, which is not possible...I don't have separate wires.
The video is the first instruction where I see a reference to "Pulse Width Modulation" which would suggest that I have this system in my car and the method of install shown in the video should work. If this is the case I will wire my car as indicated in the video. I did have a second question and that is in the wiring method the left and right turn light wires from the converter are the only wires attached to the cars lighting wires and the brake and running lights are sent to ground? Why is the running light wire not connected to the car's running light wire?
Chris R.
6/24/2020
@Bruce Your VW Golf does indeed have a combined wiring setup (with both the turn and brake signals sent along the same circuit). You're ALSO correct that it uses pulse width modulation, which is why the power module is needed (to decipher the pulses). You should be able to follow along with the video for installation.
Bob S.
9/21/2019
Audio is badly distorted cannot understand description of in-car wiring colors. Is a printed transcript available?
Jon G.
9/30/2019
I just watched the video and the audio is fine on this end so you may want to check the audio on your end to make sure everything is working properly. With that being said, there is actually a transcript under this video if you just scroll down a little. Here you can find the wiring colors mentioned but I do recommend testing your wiring on your vehicle to ensure that it is the same. We have found that sometimes manufacturers aren't consistent with their wiring colors so it's always best to double check.
Tyler
7/7/2019
Does this also work for a 17 golf alltrack? I know the gti and alltrack share a lot of the same wiring. Thanks for the info.
Rachael H.
7/11/2019
The wiring harness installed in this video is a universal wiring harness and will need to be hardwired as an installation on any vehicle. It is recommended to always test for function, and not just follow color coding when installing a hard wire wiring harness. I have also included a link to the t-one style wiring harnesses that we have that are confirmed as a fit for your 2017 VW Golf Alltrack for your reference. You might check those out, because the installation process is easier, with the wiring harness "t-ing" in behind the vehicle tail lights, and then routing a separate power wire.
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Chris
2/17/2022
why not just connect the 12 v line to the nearby cigarette lighter outlet in the hatch?