Trailer Tail Lights Flash with Passenger/Right Side Turn Signal

Question:

Im at the end of my rope here about to let go and free fall. Just finished COMPLETELY rewiring ALL of the lighting on this trailer, its STILL doing the same thing as before. Driver side works perfectly, only the lights that are supposed to are flashing. Passenger side, all the marker lights, and I mean ALL including driver side the marker lights flash with the right signal. Hit the brakes, ALL including driver side the marker lights come in. Turn on the parking lights, right brake lights come on too. Ive rechecked and redone the passenger side 4 times now, cant find anything cross wired. Even cut wires going to every one of the 3 wire lights to see if one was cross wired inside, nothing changes. Only thing I havent tried is changing the pigtails to the actual brake lights.

asked by: Ben B

Expert Reply:

The best way to troubleshooting your trailer wiring is by starting at the vehicle side with a circuit tester. I recommend running through each of the signals here with the circuit tester to make sure they are sending the correct signal when they are supposed to and not sending the signal when they are not. For example, if you have power on the trailer tail light pin when the right turn signal is active, you know the issue is on the vehicle. If the pin does not have power, work your way to the trailer and start testing the running light wire here. Start at the trailer side connector and work your way back to the tail lights until you find the cross in power. The trailer tail light is usually carried on a brown wire and the left side (passenger) is usually carried on a green wire.

If you would like to simply re-wire the trailer, I recommend using the 4-Way Trailer Wiring Harness - Wishbone Style part # A35W42B which measures 35' long.

I have attached for you below some general troubleshooting steps as well if the above does not help you locate the culprit.

expert reply by: Conner L