Trailer Lights Only Work When Headlights Are Off

Updated 06/27/2018 | Published 06/26/2018

Question:

Well, thanks to your experts I was able to partially fix my issue...I had a 7 to 4 adapter on my Tahoe and the 4 flat on the trailer was actually 7 wires going into the 4 flat so I needed a 7 to 4 with 7 full contacts. The 1st one I had only had 4 contacts inside of it. So, now my turn signals and brake lights work AS LONG as my headlights are NOT on... What am I missing here?? Thanks in advance!

asked by: William

Expert Reply:

The reason that your turn and brake lights are only working when the headlights are off is more than likely caused by a ground issue. Since the lights work as normal with the headlights off I do not believe it is a problem with the schematics. The first thing I would check is the ground for each taillight. The taillight will either ground though the mounting hardware or with a ground wire. I recommend removing the ground wire and sanding down the surface that it attaches to before hooking it back up. I would also check to make sure that both the vehicle side and trailer side connectors are grounded properly.

After you have checked all of the grounds please report back to me what your findings are and if you need further support.

expert reply by: Conner L