Testing Tail Light Wires to Install ZCI Trailer Wiring Harness on a 2018 Volkswagen Golf Alltrack

Updated 06/24/2020 | Published 09/30/2018

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Question:

I have a Tekonsha 119250 wiring system to install on my Alltrack. Can you tell me the color codes of the car tail light wiring that corresponds with the brake, turn and light circuits so that I can put the ZCI sensors on the correct wires. The tail light circuit has 4 wires going to the plug. Brown heavier gauge, black/white, black/red, and grey/black. Thanks.

asked by: David

Expert Reply:

While I do not know the wire colors/functions on your 2018 Volkswagen Golf Alltrack I can tell you how to figure it out. Use the included circuit tester that came with the ZCI harness # 119250KIT or if you need one you can get # PTW2992 to test the taillight wires while someone sits in the vehicle and goes through the various light functions.

If there is one wire that has brake lights, taillights, and turn signals on it then you only use one connector per side on the ZCI harness. You do not necessarily have to use all 4 of the connectors. If you have a wire that is brake light and turn signal and a separate wire for taillights, then you would use 2 connectors per side. But the key is testing the vehicle wires with a circuit tester.

Please note that in some cases you will need to double up the wire and then clamp the ZCI harness connector around it so that it is easier for it to sense the power running through the wires.

expert reply by: Michael H

Ken

6/22/2020

Hi, I'm looking for a wiring harness for a 2019 Volkswagen Sportwagen. I see 3 available on your website but I don't like the Curt package because it's a brand new car and I don't want to splice into the existing wire in case of warranty problems later. The Tekonsha #118730 seems perfect as it just plugs into the existing harness and the price is great ...but will it work with LED rear tailights? I really don't want to spend $265. on the Tekonsha #119250 just to tow a trailer a couple times a year. Will the #118730 work with LED tailights? Thanks in advance for your advice,

Chris R.

6/24/2020

I did some research and unfortunately the Tekonsha T-One Harness # 118730 will not work with the LED tail lights on your Golf Sportwagen. The plugs are different on the LED assemblies so the harness won't physically connect. Since there isn't another custom option, the best solution if you don't want to splice into the factory wiring is indeed the Tekonsha ZCI # 119250KIT.