Troubleshooting Trailer Lights Where Running Lights Work But Other Functions Do Not

Question:

Signal light and brake light dont work running light do car has led tail light and separate signal light.

asked by: Alfred. G

Expert Reply:

If you have a 2011-2018 Dodge Journey with LED tail lights, then the T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # 118536 you asked this question from is the correct harness. If not, I need to know your vehicle information to help.

If this is the correct harness, then it is very likely that you have a ground wire issue on your trailer. Ground wire issues often allow some functions to work and not others. I recommend checking your ground connection for a bare metal on metal connection. This wiring harness has the 3 wire to two wire connection built in that you are mentioning as many vehicles have a separate turn from brake where trailers normally combine them. If a cleaner ground connection free of corrosion, rust, and debris and being bare metal on metal doesn't solve your trailer lighting issue, then the next step is to use a circuit tester like # PTW2993 to determine where the short is. First check each function at your vehicle connection to ensure harness is working properly and then probe wires on trailer to find the short. Replace wire as needed with # 16-1-1.

I've attached videos and a wiring article to assist.

expert reply by: Jason S