2014 Ford F350 towing a mobile Suites 5th wheel. For a few days I was getting a "WIRING FAULT ON TRAILER" message when I started the truck. Then I would "OK" it and it would not come back. The brakes were all checked last year with new brake assemblies so I was pretty comfortable they would be fine and they were until they weren't. I had stopped for an overnight and the next morning I got the fault "OKed" it and as I tested the brakes I had nothing. I also did not get the "TRAILER CONNECTED" message. So, I start trying to find the source of my problem. Nothing I could find. I pull the break away plug out to see if that will activate the brakes, Ooops, forgot to unhook the 7plug from the truck. Breakaway starts smoking and melting. I grab a pair of cutters and cut the wires. After it cools I try to find what damage I had done. I find nothing save for the breakaway which is now a crispy critter. I turn the key on to see if anything looks wrong and the "TRAILER CONNECTED" message comes on. I start the truck, everything normal. I squeeze the brake control and everything looks normal, start across the parking lot and squeeze the brake controller and the brakes grab. I get up to 30 MPH or so and hit the brakes and the trailer brakes grab and work. So, I think what a lucky guy am I. I make my 400 miles that day and take today off. I bought a new breakaway rig and installed it. Plugged in and started the truck, everything seems normal.A great outcome but CAN ANYBODY TELL ME WHAT THE HELL HAPPENED? I'm thinking a short in the breakaway that burned up but why would that make the brakes totally inoperative. Thanks in advance.

 

I am thinking there is a loose wire somewhere myself.

The 7 pin connection truck side makes sense to me, but then again, if you did not touch it when parked why it would work and not work is a mystery.

 

Whenever I have weird wiring troubles on trailers, I always go through EVERYTHING and make sure ALL grounding is correct.........all the way back to the batteries on the tow vehicle. I do this first and most of the time my problems go away.

 

It’s almost always a dodgy ground somewhere, no?

Last time I had an issue a single strand of wire in my replacement 7 way plug trailer side was catching a turn signal line or something dumb. All those trailer plugs are really tight given how much abuse they take. Check grounds then connections then get ready to start getting REAL familiar with a test light and multimeter.

 

UPDATE I now have 1200 miles towing on the repair and everything has been normal except I got one 'TRAILER DISCONNECTED' and then an immediate 'TRAILER CONNECTED'. I hit a lot of very hard bumps the last couple days and somethiong may have shook loose. I've done all the grounds and the 7way is less than a year old. I don't even know where to start.

 

Pull the 7 pin connection, truck side, apart from its mount and look at the wiring connections to the plug.

That is exactly where I would begin.

The messages tell me that it is not on the 5th wheel.

 

Yeah, if you haven't checked inside the 7-way then that should be the next step.

 

Not sure but on my 2015 I have to wrap a bungee around the in bed connection. I think it's worn enough the "wiggle" driving did the connected/disconnected message.