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Troubleshooting Trailer Lights Not Working on Two Vehicles  


Put a new wire harness and lights on trailer, the right light works but the left one doesnt when i connect it to my 2014 ram pick up. But when i connect it to my 2014 jeep wrangler nothing works on the trailer


Helpful Expert Reply:

You will need to do troubleshooting for both vehicles and in order to determine the specific problem you will need to use a circuit tester such as # PTW2979 to test the connectors on your vehicles after disconnecting them from your trailer. Check the wiring going into your harness from your tail lights to see if those wires are carrying the correct signals, if not then the issue is with the vehicle wiring.

If the signals going to your harness are okay - which they likely will not be with your Jeep since you are getting no lights to work on your trailer - you'll need to test the signals coming out of the harness, and if they are correct then your issue is likely going to be with the trailer side wiring. You will also want to check both your vehicle and trailer connectors for corrosion, which can be green or white in color. A build-up of corrosion can interfere with the signals getting through the connectors so if it is present you will need to either replace the plug or clean the corrosion and be sure to use Dielectric Grease # LT37534 to help stop any future corrosion.

An important issue you will want to take a look at are the ground connections, as they can be the cause of numerous lighting problems. You'll want to make sure your grounds are securely attached to bare metal surfaces free of any paint, dirt or corrosion of any kind. Also check your wiring thoroughly to ensure there are none that are crimped, broken or otherwise damaged. I've added links to a pair of help articles on trailer wiring that you may also find useful.

expert reply by:
Kyle S

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