2007 Honda Ridgeline trailer light harness

ILLBEBAK

MEMBER
2007 HONDA RIDGELINE
72,000 MILES

All the lights on the truck work. All the lights on my TRAILER work on other vehicles. PROBLEM: using a test plug adapter on my trucks 4 prong trailer connecter, only the running lights work, the same for the trailer when hooked up. I replaced the original trucks plug thinking maybe inside the molded adapter there was a short. This did not solve the problem. I traced the wiring to up inside the driver side rear quarter panel where it is again, molded into a 2"x2" rubber piece. The last thing I want to do is to cut on the other side of THAT and try to splice new wiring. WHAT am I missing?

1 Reply

CARADIODOC

MECHANIC
33,873 POSTS

Look at the brake and signal lights on the truck and you'll see they are different bulbs. All manufacturers are doing that now to eliminate the turn signal switch from the brake light circuit to save money. That means you need an adapter harness to run the lights on a trailer that uses the normal system with one bulb for brake and signal functions.

If the truck came with a trailer tow package there are usually relays in the fuse box under the hood that will combine the brake and signal functions into one circuit for each side of the trailer. Check if those relays are installed. If someone added the trailer connector and just connected the wires to the rear lights, connecting the tail lights is simple, but then you have a single left trailer wire but two wires to pick from on the truck, the brake light or the signal light. If it was wired that way the trailer lights would only work with the brake lights OR the signal lights, but not both.