Is It Normal For 12v Power To Be On The Trailer Side 7-Way Plug When Disconnected

Updated 04/08/2024 | Published 04/04/2024

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Question:

Should I see 12v at travel trailer 7 pin plug, not connected to vehicle? I suspect my trailer batteries are draining from towing. Is this plausible assumption?

asked by: Phil

Expert Reply:

Hey Phil,

It's ok to see 12 volts on one specific pin (pictured below). It means that whoever wired it ran a line to the battery so that the 12v hot pin on your tow vehicle's 7-way can charge the trailer battery a bit while you tow. Power sitting in the wire can drain the battery but it's such a low amount that it would take a long time to really drain the battery. Typically on trailers there's a lot of other appliances (lights, monitors, etc.) that have a small drain which all together end up draining a sitting trailer battery over a month or two.

You can install a battery disconnect like # SE56VR to help prevent battery drain while your trailer is sitting in storage. I also recommend picking up a small solar panel like the Optimate # MA49JR that you can throw on the trailer tongue to keep the battery charged up while in storage.

expert reply by: Kevin C