Blown Fuse & Relay with New Utility Trailer Running Lights  

Question:

Expert Reply:

One possibility is that the running lights on the new trailer are simply drawing too much current and are blowing the fuses. Trailers can be equipped with either high-efficiency LED lights or standard incandescent bulbs, which draw about 10 times the power. If the new trailer has many more running lights than the boat trailer, and/or if they are incandescent types, then they may be overloading the vehicle wiring.

It is also possible that the running light wiring is pinched, has a bare spot somewhere on its insulation or has a bad connection at the trailer connector pin or at the light socket end. Any of these conditions could cause this symptom by creating an intermittent short. It may be that when you are at speed on the road, there is enough vibration/movement of the wiring to create the fault condition that causes your fuse and relay to fail.

I suggest you thoroughly check the ground connections on the trailer from end to end to verify that none of the possible fault conditions listed above apply. Check the trailer tongue where the ground wire attaches. Its also a good idea to check the bulbs and sockets for signs of corrosion and to confirm a secure ground connection either by their attachment hardware or ground wire. An application of dielectric grease will help to keep good connections secure.

Please note that part #118376 is not the correct harness for your Ford F-150. The correct harness is part # 40185.

Last, I have attached an FAQ article on trailer wiring that should prove helpful to you. Since your problem is specific to the one trailer, and since it is limited to just the running lights, I would focus my attention on the wiring for the running lights on the new trailer. Often this will be a brown wire.

expert reply by: Adam R

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