What Circuit on Trailer Wiring Does Blue Wire Usually Connect To

Published 10/13/2022

Question:

So there’s a blue brake wire coming up to the tongue of my trailer but it doesn’t tie into the trailer wiring harness. It’s just hanging loose. Where does that go?

asked by: Hai

Expert Reply:

Normally the brake output circuit is blue if standard trailer wiring colors were used. But since not everyone uses standard wiring colors and instead will just use what they have available you'd need to trace the wire to see where it goes. If it was the brake output circuit it would have ran from the 5:00 position of the trailer 7-way to the brake assemblies.

expert reply by: Jameson C