Troubleshooting Trailer Lights Do Not Work When Vehicle Headlights Are Turned On
Question:
Taillights work fine when headlights are off when I turn them on taillights dont signal or brake lights
asked by: Ed
Expert Reply:
It sounds like you either have a ground issue or a short in the wiring. A ground issue will usually show up when additional draw is put on the system. With the headlights on and then using the turn signal would be a typical situation like that.
You will want to make sure each light has a ground wire running to the trailer main ground or is grounded through the mounting hardware and has no sign of corrosion.
A short can be caused by a corroded or dirty trailer connector. You want to make sure the vehicle and trailer connectors are free of corrosion or dirt. You also want to make sure the trailer connectors are attached to clean bare metal surfaces.
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