Troubleshooting Trailer Turn Signal Lights Not Working Properly

Question:

All work, bulbs good. However left turn signal gets both signals working like hazards right doesn’t work at all. Brake lights work. Going for a 7 To a flat 4 connector.

asked by: Jerry P

Helpful Expert Reply:

If both turn signals on the trailer are coming on when activating just the left side turn signal in the tow vehicle then the first thing I would try and look at is the 4-Way connector on the trailer. Inspect the pins to see if there is any debris or corrosion built up that might be bridging a couple of the circuits together.

If this looks okay you will want to try and inspect the brake/turn signal circuit wires along the length of the trailer for any exposed areas that might be making contact with another wire, especially as they get closer back to the tail lights.

Also check the ground connections on the trailer, both the main harness ground and those from the individual light assemblies. Make sure they are securely attached to a clean, bare metal surface that's free of any debris or corrosion. Weak grounds can cause all kinds of weird things to happen so I definitely wouldn't rule a bad ground out as possibly being the culprit here.

If you still aren't able to resolve the issue please let me know and we can continue to troubleshoot.

expert reply by: Chris R