Troubleshooting Install of Curt Trailer Wiring Harness # C63DQ

Updated 07/06/2026 | Published 06/08/2026

Question:

i installed Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector C63DQ on my VW, everything seems correct on my part but when i went to plug in the trailer lights the left turn indicator would turn blink both lights and the right turn would not let any lights blink. The light worked correctly on my truck so i know they are not the problem. any help would be great! thank you

asked by: corey r

Expert Reply:

Hey Corey, has the trailer had any recent rewiring done on it? It sounds like some of the circuits may have gotten swapped around and now the left turn signal is actually flashing the running light circuit and if you check the wiring and address that issue you should be good.

expert reply by: Jameson C

Corey R.

6/8/2026

I did not rewire the trailer. the lights are for a bike rack on the back of the VW. They came ready to plug in, and they do work on my ford f250 properly. I thought it could be a grounding issue but it did no seem to be the problem. I took a meter to the 4pin plug out and only got a reading on the white cable, and no reading on the rest of the pins when i had someone use the turn signal or brakes. Do you think the computer module is bad?

Jameson C.

6/8/2026

@CoreyR If you have power on the white wire then yes you do have a module issue for sure and it would need to be replaced. That is supposed to be the ground circuit.

Natalie B.

7/1/2026

I recently installed the same kit in my car (2021 VW Jetta SE) and had the exact same issue. Left does both, right does nothing. The white on the 4 flat does read as ground. I also found a forum elsewhere where the same issue was mentioned