LED Trailer Tail Lights Do Not Work When Vehicle Headlights Are Turned On
Updated 05/27/2014 | Published 05/23/2014
Question:
I just change normal bulbs to led lights at the tail of my trailer. Everything seems to work fine: with out turning the lights on everything works fantastic: brake, turn signals and hazards The problem start when I turn the lights on... I dont have brake, turn signals neither hazards, just the normal tail light. May I need any kind of electrical adapter or something like that?
asked by: Albert
Helpful Expert Reply:
The problem you are having with your trailer lighting - stop and turn signals stop working when the vehicle headlights are turned on - is most often related to an issue with the ground. Trailer running lights, which are on continuously whenever the vehicle headlights are on, will draw more current than brake lights and turn signals which come on only when those functions are activated.
If the ground connection (either the main trailer connector's ground or the grounds at the light fixtures themselves) is not solid, the wiring may be able to pass enough current for some functions (like stop and turn lights) but not enough for all functions.
Inspect your trailer's main ground wire (usually a white wire) to ensure it is solidly attached to a clean bare metal surface on the trailer frame. You can sand off the paint/rust from the existing grounding point or relocate the ground wire to a new clean spot if that is easier. Also check that the ground at each light is secure. If your lights use a mounting stud to make the ground connection you can sand/clean that surface on the trailer to ensure a good connection; if they ground with a separate ground wire again make sure that the ground wire's ring terminal makes good contact with a clean bare metal surface.
Another possibility is that if you added additional lighting to the trailer the total current demand may now exceed the capacity of your wiring harness.
The linked article will give you troubleshooting guidance.
