Troubleshooting Trailer Right Turn/Brake Lamp Circuit

Updated 08/21/2020 | Published 08/19/2020

Products Featured in This Question

Hopkins Endurance 4-Way Flat Trailer Wiring Harness - 20' Long

(58)

$25.97

Hook Probe Circuit Tester

(72)

$13.47

Question:

Tail lights on trailer work but right brake and turn signal does not bulb is good are tail lights on same wire

asked by: Ken

Expert Reply:

The first thing you'll want to do is determine if the problem is on the vehicle or in the trailer wiring. With the right turn signal activated, check the pin in the 7-way in the 3:00 position with a circuit tester like # PTW2993. If the tester blinks along with the turn signal, the problem lies in the trailer wiring. If you do not get a signal, check the 7-way for damage and corrosion and repair or replace as needed. If the connector checks out okay, if the vehicle has a factory tow package, you'll want to check the power distribution box under the hood, look for a blown fuse in the 'trailer right turn' circuit. Fuse location and how it's referred to varies by vehicle manufacturer.

If the problem is in the trailer wiring, find the wire that carries the right turn/brake lamp signal. It would typically be a green wire. Trace the circuit from the trailer connector back to the right turn/brake lamp, looking for broken or pinched wires or loose connections.

Your running lights are fed by a single circuit.

I'll link you to our trailer wiring troubleshooting article, which I hope you'll find helpful.

expert reply by: Mike L