Troubleshooting Turn and Brake Signal on Trailer Not Working with Running Lights On

Question:

All the lights work on the trailer until I turn on the headlights to drive at night then the blinkers and brake lights wont work on the trailer the running lights are on

asked by: Jim

Expert Reply:

The issue you described in your question points to a weak or bad ground on the trailer. A weak ground connection usually presents itself when a larger power draw is required, such as when turning on the running lights on top of the turn and brake signals.

Your existing ground is essentially just strong enough to allow for the lower current of your turn/brake signals to go through but not enough for the running lights in addition to those circuits.

I simply recommend checking the main ground wire on your trailer to make sure you it is securely attached to a clean, bare metal surface that's free of any debris or corrosion. Also do this for the light assemblies themselves, whether they ground through a dedicated wire or their mounting hardware.

If this does not resolve the issue please let me know and we can continue to troubleshoot.

expert reply by: Chris R