How to Activate 12 Volt Power Circuit on 7-Way All the Time

Question:

I have a 7 pin wiring harness and the pin that I thought would supply aux power to the trailer is NOT live when the truck is off. This pin is live when the key is turned on and when the truck is running which makes me think it’s purpose is to charge a battery in the trailer which I don’t have. Can you offer any suggestions as to how I can make this a true aux power pin, Ie. always live. Hope this makes sense, thanks!!!

asked by: Mark M

Expert Reply:

You'd need to run a wire from the positive post of your vehicle battery through a circuit breaker like part # 9510 to the 12 volt pin on your 7-way which is the 1:00 position and you'd have the circuit active all the time. You should use 10 gauge wire for this like part # 10-1-1 (sold by the foot). Your current setup is pretty common. A lot of vehicles won't have that circuit active unless the key is on.

expert reply by: Jameson C