Brake Lights on Trailer Not Working With 2017 VW Golf SportWagen

Published 09/06/2019

Products Featured in This Question

T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector

(49)

$65.84

Cordless Circuit Tester

(15)

$19.26

Question:

You have answered to my earlier question regards the issue I am having with brake lights not working, can you tell me or have a diagram of what functions are carried over the wires on trailer side 4 pin connector Green - Right turn/stop White - Ground Yellow - Left turn/stop Brown - Taillight what about the vehicle side is this the same I can see 3 wires going to vehicle taillights turn Green wire turn yellow wire tail brown wire Do green and yellow wire carry STOP function with turn signal ? or do the brown wire carry taillights and stop function? Thanks

asked by: Paul

Expert Reply:

While we do not have a table, we do have some diagrams in the help articles I linked on trailer wiring and wiring troubleshooting which I recommend taking a look at. And even though your 2017 VW Golf SportWagen has brake lights and turn signals on the same circuit, a 4-way with a powered modulite can still have issues.

I recommend first start by checking your grounds to ensure they are securely attached to a bare metal surface free from any type of corrosion, dirt or paint; a bad ground may cause this issue because it would be unable to handle the consistent voltage output on your brakes as opposed to the intermittent output on a turn signal. It could be that when you went away for a month the connection somehow became loose or got impeded.

The other thing I recommend taking a look at, if your vehicle's brake lights don't work at all (as opposed to just when you have a trailer connected) is the fuse for your brakes, as that may have blown.

expert reply by: Kyle S

Paul

9/6/2019

Kyle S.

9/6/2019

On a trailer wiring harness, you are correct that the green is right turn/stop, the yellow is left turn/stop, the brown is the taillights and the white is the ground, as shown in the linked help article on trailer wiring. In regards to the vehicle side, the only way to know for certain what wires are for what functions is to use Circuit Tester # PTW2979 and test the wires as a helper engages the functions. That's truly the only way because wire colors vary by manufacturer.