Running Lights on Trailer Blowing Fuse  

Question:

Expert Reply:

There is likely a short circuit somewhere that is causing the fuse to blow. Let's start by disconnecting the trailer from the tow vehicle. Shorts are often caused by a dirty or corroded connector, or a damaged wire, so make sure that both the vehicle and trailer wiring harness connectors are free from corrosion and dirt. If you notice any corrosion you'll need to replace the wiring harness that is corroded, with one similar to # 118381 for a 4 way flat connector but that matches your existing harness.

With the trailer still unplugged and using a circuit tester similar to # PTW2992 , have someone turn the running lights on on your vehicle and check the voltage coming from the pin for your running lights on the vehicle trailer connector. I'm attaching our help article on wiring that will give you the diagrams on how to find which wire carries which signal for 4, 5, 6 and 7 way harnesses. If your trailer wiring harness shows voltage and the fuse doesn't blow, the short is going to be on the trailer. If the fuse does blow, the issue is originating with the vehicle.

If you can isolate the cause to the trailer, match up your pin on the wiring harness and trace back that wire as best you can to each of the running lights; make sure that none of the sections of wire are pinched, cut or damaged to where the copper inside would be touching the metal frame of the trailer- this would be the cause of your short and you will need to fix as needed.

If this still doesn't solve your problem, let me know and I will continue to troubleshoot this issue with you.

expert reply by: Erik B

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