Why Does The Blue Wire On A Nexus Motorhome 7-Way Have Power Without A Brake Controller

Updated 12/15/2025 | Published 11/09/2024

Question:

why does my nexus with mv have power to blue wire on 7 way plug when brake pressed with no controler

asked by: Mark

Expert Reply:

Hey Mark,

Wire color isn't always the same across every manufacturer so there's the chance that the wire could just be your 12v auxiliary wire. What pin is it wired to on your 7-way? When you're testing this does it have power when the brake pedal is not being depressed? If it does I'd say it's probably for a different function. It looks like Nexus does prep their motorhomes to be ready for a brake controller so if you aren't the original owner there's also the possibility that someone else installed a brake controller in a weird spot.

Let me know what you find and we can keep troubleshooting to figure out why it's doing this.

expert reply by: Kevin C

7-Way Wiring Diagram
(click to enlarge)

Jameson C.

12/15/2025

Hey Mark, what did you find when you checked which pin that blue wire was connected to on your 7-way? Once you know that, we can narrow down whether it’s tied to the brake signal or something else. Your update could really help others sorting out similar wiring setups.