Troubleshooting a Hot 7-Way Connector When the Battery Disconnect is On

Question:

7-way trailer side plug is electrically hot when trailer is on battery power. Have a 12v battery connected as a temp power source w/ 12v disconnect switch. When the disconnect is on will current backfeed to the 7-way plug? To my mind it shouldnt, but got a spark when cleaning a contact on the plug that says yes. But that means whenever the trailer is on battery power the 7-way plug is hot - which means if it gets wet or something it can short. Thanks for the help on this one....

asked by: Joe

Expert Reply:

No, it should not be back feeding into your truck's 7-Way. There could be something wrong with your disconnect: grounding, connected to the power wire incorrectly, or it's just not working. Another possibility is your trailer's brake away switch battery depending on where you have it wired compared to the disconnect. Last thing it could be is there's something wrong with the 7-Way which is why you caught a spark while cleaning it.

I recommend checking all your connections on the disconnect and moving the brake away behind it if it isn't already. Then move on to checking the wires on your 7-Way with a tester like item #

expert reply by: Jerred H