Troubleshooting Trailer Wiring Where It Stops Working When Headlights Are Off

Question:

2020 subaru outback xt, installed 118467 wiring harness and only able to get lights on trailor if turn on headlights, no brake, blinker or running, tried disconnecting battery ground and connecting back, no success, called subaru to ask if after installation of their wiring harness does car need reprogram, they said no, can you help? by the way I bought the wiring harness from you guys,

asked by: David B

Expert Reply:

There's a significantly different amount of amperage draw on vehicle's electrical system when the headlights are on vs. when they are off. When we see trailer wiring issues where the headlights being on or off is the variable that causes the issue the problem is always that the trailer wiring ground just isn't sufficient and improving that fixes the problem.

Make sure it's connected securely to a clean portion of the frame.

expert reply by: Jameson C