How To Replace 7-Way Trailer Connector On Trailer with 5 Wires

Published 10/19/2021

Question:

I have a 2015 Ford f-150 w/factory hitch and 7 blade plug. My trailer is a 2004 Big Tex with a 7 blade plug but only 5 wires. The plug got smashed and I can`t get my new 7 blade molded plug hooked up to 5 wires. Can you possibly help me ? Thanks

asked by: Dave M

Expert Reply:

In order to install a 7-way trailer connector like the 7-Way Molded Trailer Wire Connector part # H20043 on a trailer with five wires, we need to know what those wires do. I can almost guarantee what four of them are; left stop/turn, right stop/turn, running lights, and ground. If the trailer has brakes then the last wire is for the brake output. If the trailer has an on-board battery then the wire is for the battery charge line. If the trailer has backup lights or an electric actuator then the wire is for the reverse circuit.

Unfortunately, you'll need to apply power to each wire to see which circuit it actives as we can't comment on wire color since all trailers don't use the same color wires.

expert reply by: Conner L