Troubleshooting Weak Running Lights on Trailer with Curt Trailer Wiring for 2019 Toyota Prius Prime

Question:

I installed this harness on my 2019 Prius Prime for use with a small utility trailer. The side marker lights seem okay but the tail-lights on both sides are barely illuminated. Completely illegal and unusable. With the covers off I can see the bulbs are barely glowing. Should I be running LED trailer lights or is there another issue...? This has nothing to do with my installation bcs obviously there is power correct....?

asked by: Ash

Helpful Expert Reply:

What you described sounds like a weak ground circuit for the taillights that aren't able to illuminate all the way. The Curt trailer wiring harness # C56371 that you referenced is capable of putting out 6 amps on the running light circuit so it would not be the harness unable to provide the amperage needed. Typically when this issue occurs it's that the taillight assemblies are not grounded properly or the main ground of the trailer's wiring isn't attached to a clean metal surface.

expert reply by: Jameson C