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Troubleshooting 12v Power Pin On 2017 Ford F-350 Not Working


I have 2017 F350 that won’t send 12V to the trailer to keep the battery charged. I read that the 2017 and newer don’t need the fuse in spot 27 or the relay in spot 37. My truck doesn’t have any female pegs to put the fuse and relay into. Theses trucks activate the 12v to the trailer when the truck recognizes a trailer and the brake is pressed. The problem I have is that even after doing that, I still get no power going to the trailer battery. I have checked the fuses and haven’t found any blown. Any help would be appreciated. Thank You,


Expert Reply:

The only way that your 2017 Ford F-350 would not need the Fuse 27 and Relay 37 for the 12v power circuit on the 7-way connector is if it has the OEM trailer brake controller.

With the OEM controller the computer detects a trailer is connected, and then sends the 12v power.

I recommend using a circuit tester like # PTW2993 to check the 12v power wire on the trailer side connector with the truck connected to the trailer to see if power is making it through the connector. If you are not getting power, then check the wire in the 1 o'clock position of the trucks 7-way connector to see if the truck is actually sending power or not.

If you are not getting power, you will need to trace the power wire back and look for any damage to the wire that could be causing power to not make it back to the trailer.

Keep in mind that the 12v power circuit will not charge a low or dead trailer battery, it will only put a small maintenance charge.

If you cannot find any issues you will need to take the truck in to your local Ford dealer to have them troubleshoot the issue.

I included a link to a helpful article on wiring for you to take a look at.

expert reply by:
Samuel C

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