"Check Trailer Wiring" and "Trailer Brakes Connected" and intermittent loss of trailer brakes

[Boudicca908]

17 hours ago, Wayfinder said:

sounds so similar to my own break issues

This does seem to be a common problem. People have resolved in different ways, having found different causes.  By the way -- we did replace my brake wires in both front and rear axles, but the original rear axle wire was left abandoned in the rear axle. Unfortunately I didn't pull it out that day, because we were working against the clock, trying to finish as the sun was setting. Now it's a lot harder to access. I hope to get it out of there to inspect it though, because I really want to see it. Thanks @Wayfinder for linking the image of your frayed wire -- Wow! That is a mess. The jury is out on my 'fix' and time will tell. 

[Boudicca908]

UPDATE on August 9, 2026:

It has now been 1,800 miles of towing since the wiring work, and NO warning messages have been appearing on my Tow Vehicle ....  I believe @ScubaRx is correct that we had the right avenue for my particular fix. I will update again, if it comes back. Thanks again to @jd1923 and @ScubaRx for all of their help, and to @jd1923's family for their gracious hospitality in Prescott. 

[Sweis]

2025 Ford lariat F150Having the same intermittent warning pop up on my dash. Legacy elite two 2021 hull 707.

Brakes look like they had some mileage exchanged with four new Dexter backing plate brake combo. Worked fine. All the slow drives. I did around neighborhood to test.
 

First trip up through George started getting warnings and brakes would basically shut off. Checked all my connections 23 times when sitting still operated fine about 3 A at each break 14 A when tested at the breakaway switch finally saw the threads about the wire in the axle pulled the front one out. There was a few rubbed spots.  eventually  would’ve failed but found about the middle of the wire in the axle.  looked like somebody had set a hot welding rod a piece of hot metaldown on the wire in a couple places. Didn’t have any wire yet so cut the bad section sliced back together taped it to the axle. Seems to be working fine a couple hundred miles. 
 

Ordered some new marine grade  Wire and some “solder butt connectors” comes with small heat gun.  shrink wraps, and solders at the same time. Will attach the wire to the outside of the axle.