Could Center Pin of Trailer Wiring 7-Way be 12 Volt Accessory Circuit

Updated 03/28/2024 | Published 06/27/2018

Question:

I have a 1999 Ford F-250. Factory tow package. Its being hooked up to a enclosed trailer with its own battery and a 7 pin connection. Im trying to test the 7 pin on my truck and it seems a little off from standard. With the truck running and the lights off, the only post that is receiving power is the center post. This would lead me to believe the center is wired as the Aux power and not reverse lights. I have verified that my 30 amp fuse is good and my trailer battery charging relay under the hood is working. In my research, once in a while I see a post that says the center pin can be reverse/aux. How do I verify? I just want to make sure that if its always powered when the truck is on, its the correct circuit for trailer battery charging.

asked by: Kellen

Expert Reply:

You basically already did verify that the center post of your 7-way is the 12 volt accessory circuit. Normally the center post is the reverse light circuit and the 12 volt pin is the 1:00 pin position. If your center pin is hot all the time then it would be the 12 volt accy circuit.

expert reply by: Jameson C

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Kenney

3/20/2024

I had 30 amp fused 12 v going to 5 o clock and the green brake at the 1 o clock. I am wiring for a brake controller so I made the 12 v at 5 o clock, a Battery + to 40 amp to 1 O clock. And I moved the green brake to 5 o clock. Now, I still have a 12 v 30 amp fused at the center reverse. Is it ok? or what do I do with a 12 v at 1 o clock and at center? Thank you very much and bless your heart for trying to understand and reply to all our needs. Thanks again. Kenney

Jameson C.

3/28/2024

@Kenney The center pin of a 7-way is typically used for a reverse light circuit but it's also considered by some to be an aux 12 volt power circuit. Or basically you can use it for whatever you want as long as the matching 7-way is wired up the same. All of the changes you made are totally fine as well.