Troubleshooting Brake Lights that Stop Working When Running Lights Turn On

Question:

all lights work on my boat trailer however when running lights come on brake lights wont work. what could that be?

asked by: Anthony S

Expert Reply:

It sounds like you have a weak ground connection somewhere on your trailer. The running lights will require the most power draw on the system, so when these are on, there is not enough left to also activate the brake lights. This is typically an indication of a bad or weak ground.

I recommend checking that all your ground connections are made to clean, bare metal surfaces that are free of any debris or corrosion. Check the light assemblies themselves to make sure they are grounded properly. Whether the assemblies ground via a dedicated wire or through the mounting hardware, make sure all the connections are secure and sound.

If you are still not able to resolve the issue, please let me know and I will be happy to look into this further. I have also attached a couple of trailer wiring articles that you might find helpful.

expert reply by: Chris R