What to Do w/ the Black and Red Wire When Wiring a 7-Way Connector

Question:

Im trying to rewire the 4pin from trailer to 7pin harness cord and have a red and black wire from 7pin that are left over. What do I do with them?

asked by: Jerryskidx2

Expert Reply:

The black wire is usually the 12v power wire that typically goes in the 11 o'clock position on the trailer side 7-way connector as you are looking directly at the front of it. It'll keep your battery charged, run an electric jack, or something along those lines. Not the end of the world if you don't have anything to run it to. Now the red wire is going to do something with your left side trailer lights if you are wiring your 7-way in a standard configuration so it's pretty important.

I have linked a diagram below that will show you how to set up your 7-way. It is best to use a circuit tester like item # PTW2993 when doing trailer wiring so you can match up the wiring with the correct pin. You can also physically trace the wires from the connector to where they end up to discover their functions. Another option is to apply power to each wire using a separate 12-volt battery and see what light or function turns on.

expert reply by: Jerred H