Trailer Brakes Shorting Out - Controller shows overload

Do the trailer brake wires run inside the axles from one side to other?
If Yes...wire probably has been chaffed causing insulation to break down.

Don't tip-toe around the useless warranty, fix your wiring. The axle issue mentioned is a good place to start, if that doesn't fix it pull the hubs and look for wiring faults in the magnet wires. Problems in the truck receptacle, trailer plug and any of the wiring back to the axle are other possibilities.

Derek,

Some background please:
How many brakes?
On how many Axles?

Get a compass.
Track the brake wiring and inspect it all.
There are often connections near the backing plate that can be separated. If you have those, you are in luck. If the brake control is two separate wires anyplace, put the compass near each and have someone step on the brake. by comparing the result, you will know which is the shorted magnet.

If it is a shorted magnet, you will probably have to pull the drum to replace it (or repair it if you can identify the issue).

Matt

I had a similar issue on a new trailer, it would intermittently show a short when moving. Dealership could not find it, it was still under warranty. Every time they said it was fixed I would pick it up and short would show up on the way home. I isolated the problem by jacking the trailer up and spin one wheel at a time until the brake controller indicated a short. Brought it to the dealership and pointed to the wheel that was causing it, when they removed the drum the brake wire had come loose from the clip inside and was just barely rubbing on the inside of the drum. They fixed the wire and have not had any trouble since.

The trailer has two 3500lb axles with 10" drum brakes on each wheel. Yes the wires run through the axle tubes. Here is what I have done as far as diagnosis so far.

1. Had son max out the controller manually to 11 on the meter. I shook, moved touched all the wires and no shorts were shown. The problem only shows up when the trailer is in motion.



2. I pulled all the drums off, checked wires and once again had son put power to the system while I moved the brake arm. No short found. Wires looked ok.

The trailer only has maybe 1500-2000 miles on it - so I thought about the inside the axle tube chafing issue - but my dealer warned me about the warranty issues if I started cutting wires.

I don't think the issue is with the car or the controller, hooked the trailer up to another truck and it did the same thing. It felt different almost like a chug-chug-chug as the brakes were being applied. The biggest issue I have is that the short only shows when the trailer is moving. Only way I can think to narrow it down is to start cutting or disconnecting wires and narrow down where the issue lies.

@dman535, if you know how to pull off the drums you can fix this. Yes, the dealer *should* fix this under warranty, but in my view I would rather fix it myself than put my camping season on hold waiting for a dealer appt. BTW, you're only "voiding the warranty" on this issue, not the whole trailer.

Even if you replaced all of the wiring between the tongue and the brakes, it's not that big of a job. You can get some good quality marine duplex wire at good prices here at Best Boat Wire. Just run new wire and zip tie to the outside of the back of the axle...get some waterproof crimp connectors to attach to the brake magnet leads. Some folks have upgraded the wire to #12 to minimize voltage drop and improve brake performance.

You may never find the problem but at least the brakes will be fixed and the camping can resume!

I started by cutting the power wire to the passenger side front axle, no change. Then cut the drivers side - an no more short. I reconnected the passenger side and have three drums running without issue. I can only assume at this point that the magnet in one axle is causing the problem.
Unless - just removing one wheel caused enough of a current drop not to trigger the overload.

I had the low vtage thing on my 10 year trailor, i didnt have the option of another tow vehicle. So consider yourself ahead of the game. I changed and redid all the grounds, re-did all the connections. I eventually had to rewire. Do that first, not that hard. I wasted a few days troubleshooting and not doing. After you check the grounds. That is unless your good woth a meter, bit then the problem cluld be while your rolling and may not be a problem while its sitting. And dont forget the e break switch eaither.

Old-Biscuit wrote:
Do the trailer brake wires run inside the axles from one side to other?
If Yes...wire probably has been chaffed causing insulation to break down.

that is what happened to us and the fix is run a wire on the rear of the axle tube and zip tie and connect the wires.

chevman

dman, the wires could also be chafing where they pass through the backing plate from the magnet to the main wiring. The hole in the backing plate might be missing the rubber grommet that's supposed to be there. Check the wiring right up to the magnet, magnets very rarely go bad and just short out, especially with that few miles. If it does turn out to be the magnet you can order one online at eTrailer. Just have the details from the sticker that should be on the axle tube to be sure you get the right parts.

BTW, nice work on the diagnostics! Feels good to have it fixed vs. waiting a month for the dealer to tell you they couldn't find any problems....