Which Pin On A 7-Way Should Have Constant 12V Power When Vehicle Is Running
Updated 07/01/2025 | Published 09/22/2019
Question:
Is any prong of the female 7 point light harness suppose to be continuously hot? The black is showing consistent power and my brakes on my trailer engage when I connect my lights but I’m not braking!
asked by: Byron
Expert Reply:
The only pin that should be continuously showing 12V power on the 7-Way connector on your vehicle is the 12V power circuit which is normally the black wire but not always. In 7-way wiring the 12V auxiliary power feed is carried on the contact at the 1:00 position as you look at the socket. I have added a photo that shows you the pin positions. I recommend to use a circuit tester like part # PTW2992 to test the pins on your 7-way for power. If the brake output is the one with constant power then that is why your brakes engage when you plug your trailer in. You do not want full 12V constant power at the brake output circuit unless you can activated the manual override on your brake controller.
If you have full 12V constant power on the brake output the first thing you want to do is test your brake controller to see if it's bad, sever the blue wire from the back of the brake controller about 7 inches back from the brake controller. Test the blue wire from the brake controller for power. If it has constant 12V power without activating the manual override then the brake controller is bad and needs to be replaced. If you only have power when you activate the manual override on the blue wire then there is a short somewhere between the brake controller and the 7-way connector.
In that case you would want to check the blue wire between the brake controller and 7-way for frayed wire or a short somewhere.
Paul S.
6/17/2025
This was helpful with cutting the blue wire. When I cut it the brake controller is now flashing, before it was on all the time. Any thoughts on this?
Heather A.
7/1/2025
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Terry
3/11/2025
Hello Heather, I was wondering if you could tell me if a 7way camper plug should get hot while I'm towing, I just purchased a newer camper and while getting it home 10 miles away, I noticed that the plug when disconnecting was a little warm. Is that normal?