Troubleshooting Running Lights Come On Then Shut Off On Trailer

Question:

New to me trailer, changed out the pig-tail on trailer side and ran it to a junction box. truck is a 2020 gmc 2500 hd. running lights will only come on for a second then a hard off. changed out hitch on truck still same issue.

asked by: Chad U

Expert Reply:

It sounds like you either have a weak/bad ground or your lights are drawing too much power. In order to find the problem lets start by double checking the connector on your 2020 GMC Sierra 2500. Using a circuit tester like # PTW2993, check for power on the running light circuit. More than likely you have constant power here and the issue is on the trailer side.

If it is on the trailer side I would start by inspecting the connector. Make sure it is free from debris and corrosion. From there, double check your ground wires and make sure they are secure on a clean, bare-metal surface. You can also double check the running light wire to make sure it isn't damaged.

To check and see if the lights are drawing too much power, you can disconnect some of the lights and see if the same thing happens. If it does, I recommend switching to LED running lights like # MCL31AB. You would need to convert your other lights to LED as well.

expert reply by: Robin H