Troubleshooting a 2020 Jetta R-Line With No Working Driver Side Signals

Updated 08/05/2024 | Published 03/28/2024

Question:

I installed Tekonsha 118791 on my 2020 Jetta R Line. The right turn signal is powering both left and right at the plug. The left turn drivers side gets no power at the plug at all. The running lights are at 12v but I haven’t tested the brakes yet. My legs aren’t long enough. Any suggestions?

asked by: Monty C

Expert Reply:

Monty, the first thing I'd do is make sure everything is plugged in properly and the connectors aren't damaged in any way. The next thing, and honestly the last thing you can check is the fuses.

Since the T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # 118791 just plugs into your factory wiring and does not require any splicing there shouldn't have been any issue with the wiring itself, so it leads me to believe the fuse might be blown on the power wire.

It also wouldn't hurt to check your ground and make sure that's not loose and attached to a clean bare metal surface. If that all comes back fine, then you might just have a faulty harness and would just need to replace it.

expert reply by: Bryce D

Monty

3/28/2024

I went through all the wiring last night and used the vehicle ground. I have a good ground and I’m getting power to the box.

Bryce D.

3/28/2024

@Monty That's strange, so then that leads me to believe that the harness itself might just be faulty. If the wiring is good and you're getting power there should be no reason it does not work.

Joe P.

8/4/2024

@BryceD Sir, I am also having a similar issue. The left turn provides now power and the right turn provides power to both left and right. The brake lights and running lights work as intended. If you swap the connections from right to left, the left light provides the power that the right side previously provided. The fuse is in tact, the module is properly grounded, and everything has been hooked up per the instructions provided. Could this be due to the fact that the R-Line's brake lights and turn signal are not separated? Or does that have no bearing on the outcome?

Bryce D.

8/5/2024

@JoeP That should not matter. if the left hand turn signals only come on when the right side is turned on then it's either a bad ground to either the trailer or lights, or it's a bad connector. Since you've checked the ground already, I'm betting it's a bad connector.