2003 F-350 7.3L pulling Hart LQ horse trailer (approx 14,000#). Situation: Because of rising trans temp, we made a decision to return home from a Labor Day horse riding trip to Missouri. We were two hours from home. At one point, I decided I needed to pull over NOW to cool things off and I made a rather hard stop on Interstate, not an emergency stop, but put good pressure on brakes. Pulled over to side of road, trailer brakes locked up, brake controller light goes out. Checked all connections and fuses. Nothing seemed out of sorts. Had to unplug trailer brakes to free up brakes. Drove home with no trailer brakes. Not good.

Took truck to RV Center. Purchased new brake controller: Prodigy. Also purchased new plug for trailer brake line. Installed both. NOTE: original trailer plug on this trailer looked very dark inside each plug channel, kind of charred.

When getting new trailer brake plug installed, everything worked except running lights. Discovered that fuse #38 was blown. Replaced fuse. All well.

Took trailer out yesterday for weekend horse camping trip. Got only 10 miles from home, Prodigy starts flashing a code that means there is a short in brake wire at idle. Called RV Center. Guy says if I still have brakes, don't worry about it. Reluctantly, continued trip. Within 1 mile, Prodigy flashes new code. This one indicates loss of power to trailer brakes! This code flashes intermittently. Now, I'm worried. Turn around and go back home.

We have another, smaller horse trailer. Transfer horses to small trailer and travel 90 minutes away for some trail riding. No odd codes from Prodigy. No issues. However, on way back home we turn on lights. No running lights on this trailer now!!! Upon checking this morning, fuse #38 was blown again. Replaced fuse, running lights work on smaller trailer.

My opinion: The Hart trailer has a trailer brake wiring issue. There is a short in a wire. Or, a wire is somehow exposed and is touching something. Or, the trailer brakes won't fully release.

My question for you folks here is what are your ideas of the cause of this issue? Do you concur with my thoughts? What other culprits could there be that I'm not considering?

I would agree the wiring is the first issue to check. I have a hard time believing the brakes "Lock" up mechanicly.

Believe the fuse. It burns out when too much current is passed.

It turns out that we had a loose wire coming from the rear junction box going to one of the brakes. I hope that was the only issue! But, so far, based on one test run, it seems to be. We will be taking the trailer out for a shake down this weekend and then on a major week-long trip the following weekend. Fingers crossed.

BTW, the tech folks at Teconsha (Prodigy) and Hart were great to work with.

Got the trailer back from the trailer shop. I was told that one of the brake wires from the rear junction box to a brake was loose. Now that it is good-N-tight, I should be good to go.

We have a week-long vacation coming up the first week in Oct., so this weekend was to be a shakedown overnight trip to a nearby horse camp. If all went well, we'd be set for the longer trip. And, this coming Monday I'm having a few mods done to the F-350, so I'm excited.

Unfortunately, things did not go well at all. Twenty minutes from home we started to get the "SH" error code on the Prodigy again. This time I figured maybe it was just the Prodigy being too sensitive. I ignored the code and drove on. Within five minutes the trailer brakes suddenly grabbed, then let go. Just a little, but enough to know that something just happened. I had hardly uttered the words "this isn't good," when they did it again, and again and then locked up! This gets your attention when you are at highway speeds!

We pulled off the road and I unplugged the trailer from the truck. Home we went, another weekend trip ruined and back to Square One. It looks like we are going to cancel our vacation, too. Even if a mechanic says he has this fixed, I wouldn't feel good about making the first trip with a "fixed" trailer a 6-hour trip from home. I'd say there's a 50/50 chance that this trailer is getting ready to be traded in.

Okay, the trailer was checked out stem to stern. All systems check out fine. My mechanic took all the wheels off, pulled all the wires, checked the magnets. No issues! Which is really troubling me.

We have decided I am going to swap out the new Prodigy brake controller. What else could it be?

One thing is nagging at me. You see, the Prodigy unit is the SECOND brake controller I've had. Both indicated a short somewhere. With both controllers the trailer brakes pulsed and grabbed and finally locked on tight, without me pressing on the brake pedal. And, every time this has happened it's been in my large trailer and only when it's been loaded down with horses and gear, never when I've pulled that trailer empty.

So, here's what is nagging at me:

The only change to my setup that was made before I had the FIRST trailer brake SNAFU was the installation of SuperSprings. That's it, that's the only modification I had made to the setup. Is there ANY possible way there is a wire from the brake controller to the rear plug on my truck that is getting pinched when there is a heavy load on the truck? It would have to be only when the load is really heavy, such as when the big trailer is loaded down with horses and gear.