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Troubleshooting No Power on a 12v Power Pin on a 7-way Harness on a 2020 Ford F-350


I purchase a 7 way plus that has lights that tell you blinkers power reverse lights and 12v power etc. When I plug that into my truck I cannot get the 12v light to come on. This is what is supposed to charge the camper while connected to the truck, with the truck running. I am at a loss and have no idea how to activate this pro get it to work! I have checked the fuse under the hood fuse 7 I think it is there and not blown. Truck was running, key inside and doors shut found this on the internet. I even tried putting truck in neutral and still no luck... How do I get this thing to activate the 12v power to the 5th wheel or even to my dummy plug? Any help would be much appreciated.


Expert Reply:

The first thing you need to do is check the appropriate fuses on your vehicle for a blown fuse on your 2020 Ford F-350 super duty. If everything looks good with the fuses, I recommend checking for shorts or fraying in the 12v wiring anywhere from the plug to where the harness connects to the front of the vehicle. This can be done at different points of the wiring with a circuit tester # PTW2993. It is also important to check and make sure the ground wires on your harness are mounted to clean metal surfaces.

As a last resort, there is a way to run a power line from the 12v pin on your 7-way plug to your battery. Typically, the power pin on your 7-way is in the 1 o'clock position on the harness. I went ahead and attached a photo that shows you the typical layout (both front and back).

The way to do this is to run the length from your plug to your battery while using 10-gauge wire # 10-1-1 (which is sold by the foot). One end plugs into the 12v pin on the 7-way plug while the other hooks to the positive battery terminal with the # 9510 40 amp circuit breaker. In order to connect to the terminals, you need You'd need two # DW05741-1 ring terminals to connect to the breaker and a # 44-5356A ring terminal to connect at the battery.

This setup provides you with the power you need. Once you are done, you can confirm the pin by using your dummy tester plug like the # TR20117.

Typical 7-Pin Layout with Front (left side) and Rear (right side) View
Typical 7-Pin Layout with Front (left side) and Rear (right side) View
(click to enlarge)
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