I have checked the connection on the truck and all are working fine but when the trailer is hooked up I have turn signals and running lights but no brake lights and with the running lights on I press the brake and the lights go out.

Any suggestions?

  • Double check the Earth wiring.
    – Autistic
    Mar 31, 2016 at 9:26

1 Answer 1


It sounds like you have a ground issue. When the running lights are on they are actually grounding through the brake lights. When you apply the brakes it cuts off the ground and the lights go out. The turn signals only look like their working. They are probably turning on and off when they should be getting brighter and dimmer.

Double check the wiring on the trailer and that the ground line has a good connection.

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