How To Wire In A 7-Way To Replace A 5-Way Flat  

Expert Reply:

You can install the 7 way plug in place of the 5-way that is installed on your trailer currently. The colors would not 100% match up. But white would go with white which is your ground wire. Green goes to green which is your right turn signal. Yellow goes to yellow that is your left turn signal. The black wire goes to the battery. It's a lot better to test them by function.

There will be two additional wires, The blue wires goes to the brakes and the wiring let alone will be the auxiliary wire. If your color of wires is different you would need to trace the wires and see what function that they have or you could use The Hook Probe Circuit Tester # PTW2993. Using this tester will let you test your connections easier and will let you know which wire has what function.

I attached a review video link below

ETBC7 Wiring Diagram
(click to enlarge)