Trailer Running Lamp Fuse/Relay Location on 2010 Ford F-350 Diesel
Question:
Hi there, Do you know where the fuse is located for the trailer runnings lights on 2010 F350 diesel? All of the other trailer functions work but my running lights will not turn on. Also, perhaps there is a switch I am missing in the truck to turn on running lights? Trailer isn’t the issue as when I use a different vehicle, everything works.
asked by: Jessica
Helpful Expert Reply:
You did a good job trying the trailer on a different vehicle. This pretty much confirms that the problem lies on the truck side of the equation, but there still could be an issue on the trailer itself.
The fuse and relay for the trailer running lamp circuit are located in the power distribution box in the engine compartment. Check the 30A fuse in location # 42 and the relay in location 55.
If you find that the fuse was bad, replace it but before plugging the trailer back in you'll need to find the short in the running lamp circuit on the trailer that caused the fuse to blow in the first place or you'll be continually replacing fuses. Beginning at the trailer connector, trace the running lamp circuit (typically carried by a brown wire) from the connector back to the lamps. Look for pinched wires or loose connections or wire insulation that's worn through or cracked that would allow the copper wire to short out on the trailer frame. A common spot for worn wire insulation is where the wire passes through holes in the frame members.
I'll link you to a trailer wire troubleshooting article that you might find helpful.
