Right Turn and Stop Signal Works on 2017 Road King Trailer but Left Turn and Stop Dont

Updated 08/06/2018 | Published 08/04/2018

Question:

I have a 2017 Road King twin axle hydraulic brake boat trailer. The trailer connects to the tow vehicle GMC Sierra 1500 via a 5 point harness to an adapter to the truck. When I hooked it up to my tow vehicle the left trailer brake light won’t illuminate. I turned the hazards on, depressed the brake pedal and engaged the turn signal. The left light does illuminate but no brake or turn signal when I turn the tow vehicle’s lights on. The right trailer brake light works as advertised. I used two different 5 pin adapters when I troubleshot the issues. Thanks for all of your help in this matter!

asked by: Brian

Expert Reply:

This sounds like a simple case of a bad ground on your 2017 Road King. It could be on your 2017 GMC Sierra 1500 but since the right side of your trailer works fine I think the issue is on the trailer side of things.

Check the connector on your trailer and make sure that everything is clean and corrosion-free and then move on to the grounds. Check the grounds for the lights on the left side of your trailer and make sure they are securely connected to a clean, bare-metal surface. Sometimes even some paint can cause issues.

Let me know if this doesn't fix your problem and I can help you troubleshoot further. I am also attaching a link to a helpful article we have on troubleshooting trailer lights for you to check out.

expert reply by: Jon G