Does Black Wire on 7-Way Go To 12V Power

Updated 06/21/2022 | Published 06/18/2022

Question:

My equipment isn’t using the black wire on 7 way plug , I wanna know how and where it comes from so I can charge my batter in my tow vehicle while driving?

asked by: Jim

Expert Reply:

Typically the black wire on a trailer 7-Way like the Hopkins # HM20048 is for 12V power. It will run from the positive battery terminal on your tow vehicle back to your trailer battery or whatever you're needing to power (like interior lights).

With that being said there are a few things I want to clarify before you start making connections; you'll need to charge your tow vehicle battery with an alternator - not the trailer battery (that seemed like what you're doing with how you worded your question), and just because the black wire is typically used for 12V power doesn't mean that's the case for your application. The color of trailer wiring can vary between setups since the only thing that really matters is the gauge used and that it's connected to the proper function. You'll want to test that black wire or trace it to see where it goes prior to connecting it to a function.

expert reply by: Jon G