Left Turn Signal On 7-Way Trailer Connector is Not Working

Question:

My left side wire for trailer on truck has no power. Chased. Itfytther back lookd like ot runs further in to truck. How can i figure this out?

asked by: Ilario F

Expert Reply:

It is possible that there is a blown fuse or relay related to the tow package wiring that is causing the problem. Use the vehicle owner's manual to find the locations.

It is also possible that there is a break in the wire somewhere. You will need to use a circuit tester like # PTW2993 if needed to test the wire as you work your way forward on the truck.

If the right side stop light also does not work, it could be a blown stop light or CHMSL fuse. If the turn signal function works on that same circuit (a 7-Way has combined brake and turn signals at the 3:00 and 9:00 positions) then it could be a dirty or corroded trailer connector.

expert reply by: Michael H

Matthew P.

10/31/2021

The connector looks good and clean, should I replace the wiring harness then?

Les D.

11/1/2021

@MatthewP Please tell me more about your vehicle and trailer, and the issue you are experiencing and I will try to come up with a solution.

Matthew P.

11/1/2021

@LesD 2019 Yukon SLT, left trailer break light will not work. Already changed out the fuses. Connector looks clean. Waiting for more tools to arrive to test further. Shop said that they tested the trailer on their vehicle and the lights worked.

Les D.

11/2/2021

First is it possible that you have a bad bulb in that fixture? Assuming that you have neither brake light or running light. Ok, let's take this step by step. With the trailer disconnected from the Yukon, do the lights and blinkers on the Yukon work? If so, with the trailer disconnected, check the pins on the connector on the bumper of the Yukon. It would be easiest to test with the Draw-Tite # 40376 tester. Do all the blinkers work correctly? If not check the connections on the back of the 7-way connector on your Yukon bumper. Also check your connections inside the connector for rust, corrosion, and dirt. If bad, replace. Also check the white wire that comes out of the back of the Yukon 7-way connector. Verify that it connects to a grounded Yukon frame part and that the ring on the end of the wire is clean and bright, and that the place where it connects to the frame is clean and bright. Use a wire brush if not. Yes, it would be ideal to, do what the shop did, and hitch up something else to the Yukon. This will prove that the problem is, or is not, with the Yukon. If Yukon seems to be working correctly, check the connector from your trailer to see that all is clean and corrosion free. No on the back of the trailer connector pay special attention to the yellow wire for the left brake light. If you have power there, then trace the wire checking for any nicks, cuts, crimps or abrasions. Finally check the light fixture for damage. Check the ground on the back of the light. I have attached an article that discusses trailer wiring. Yes, it would be ideal to do what the shop did and hitch up something else to the Yukon. This will prove that the problem is, or is not, with the Yukon. If Yukon seems to be working corrrectly, check the connector

Helpful Links

faq-wiring.aspx