Troubleshooting Blown Fuses on 2018 F-350 After Adding Lights to Trailer

Question:

I have a 2018 F-350 power stroke 6.7 L. I wired my boat trailer with 12 gauge pacer wire American made. I ran two separate wires to reverse lights going to a relay. So my wire is this 1 12gauge wire to right side reverse lights 1 80 watt 1 20 watt the left side is the same configuration. I ran those wires to a relay with the trigger to reverse lights and the hot being the AUX/battery charge. They function correctly, the issues is I blew fuse 65 trailer tow lighting module. I did notice I did not have a fuse in the 27 trailer battery charge spot. Although the line was hot? The light worked for about 1 min the it blew the fuse in 65 spot. If I put the fuse In 27 would that allow the 65 not to blow? Also am I trying to run to much light? 2 80W 2 20watt with a combined 200 watt if my math is right that’s 16.66 amps. Would I be better off running Upfitter switch 6 40amp to the trailer plug and cutting the battery charge from plug and wiring In the upfitter to it? Please advice.

asked by: Logan W

Expert Reply:

Thank you for all of the details!

Adding 16.66 amps to your trailer tow lighting module could definitely have put it over the top since you added lights to what already existed on your trailer. If you don't plan on using that 12V power for a battery charge then there isn't any harm in using that to power your lighting. You can run it to the Upfitter switch if you want but my only hesitation with that is if you forget to flip that switch and then your lights don't come on like they need to.

I'm not sure why there would be power back at the 12V power pin if there isn't a fuse in that 27 position unless your 2018 F-350 has it in the 38 position instead (which is for non-trailer brake controller pickups). You might also consider tossing in an auto-resetting circuit breaker like part # PK54530 to keep from having to replace anymore fuses.

expert reply by: Jon G