trailer brake problem

“intermittent issue with the brakes working about half the time”

So half the time you can’t stop? I suggest a pro look at your brakes for MY safety.

dryfly wrote:
Recently installed 4 new electric brake assemblies and Prodigy P3 controller. Worked great for 800 miles.

Plugged the trailer in one morning and got a "Short" error on the controller. Checked all truck/trailer wiring and nothing evident. Next time I plugged in trailer I got an "Overload" error. Prodigy tech support this does not indicate a short to ground but that the system is drawing too much current.

This has evolved into a highly intermittent issue with the brakes working about half the time and getting the "Overload" the other half. I have eliminated the truck and controller as being part of the problem.

Obviously it has to be wiring in trailer or brake magnets causing the problem. The error will not occur with the truck setting still, but it just doesn't react like a wiring issue, and should show up as a "short" error if it was wiring.

Is it possible that the magnets could be breaking down internally under load of breaking??

The magnets should be fine with the miles indicated. Unless the assemblies were installed wrong...

Both controller messages are indicative of trailer side wiring issues. First place to start is the cross over wire inside the axle housing. These chafe and the insulation cracks causing both types of error.

Short error would be a cross connection on the brake positive and negative wires.

Overload could be multiple issues, but most common is brake positive contacting the axle housing.

Check any wire nuts and scotch lok wire connectors -they fail but look outwardly fine.

Magnets can fail and have internal shorts. You are going to have to disconnect one magnet at a time to determine which one is at fault.

In my trailer, if I ever have to do any brake wiring work, I will homerun every magnet to a common connection in a distribution box so that troubleshooting something like that is easier.

Use an ohmeter and measure between the brake terminal and ground of your trailer connector with it unplugged. Since magnets are typically a little over 3 ohms, you should measure slightly below 1 ohm for the 4 of them in parallel.

dryfly wrote:
Is it possible that the magnets could be breaking down internally under load of breaking??

Were the magnets replaced?

Here's my story: I had a Prodigy controller that was showing an error code. I replaced it with a Prodigy P2. The error code was still displayed. I traced it to a break of the copper inside the jacket of one of my umbilical connections on the truck. I must have tossed up a rock and it was enough to part the copper but not enough to break the jacket.
I disassembled the umbilical connector on the truck, stripped back to good wire and reassembled. All is now good.

mapguy wrote:

dryfly wrote:

The magnets should be fine with the miles indicated. Unless the assemblies were installed wrong...

Both controller messages are indicative of trailer side wiring issues. First place to start is the cross over wire inside the axle housing. These chafe and the insulation cracks causing both types of error.

Short error would be a cross connection on the brake positive and negative wires.

Overload could be multiple issues, but most common is brake positive contacting the axle housing.

Check any wire nuts and scotch lok wire connectors -they fail but look outwardly fine.

Assemblies were installed correctly. I thought about the cross over wire inside the axle tube. I think I will pull the wire and examine, but I feel if this were the case, I would be getting the error with the truck sitting still at some point while manually applying voltage to the brakes.

babock wrote:
Magnets can fail and have internal shorts. You are going to have to disconnect one magnet at a time to determine which one is at fault.

In my trailer, if I ever have to do any brake wiring work, I will homerun every magnet to a common connection in a distribution box so that troubleshooting something like that is easier.

Use an ohmeter and measure between the brake terminal and ground of your trailer connector with it unplugged. Since magnets are typically a little over 3 ohms, you should measure slightly below 1 ohm for the 4 of them in parallel.

I agree on testing one brake at a time. At this point it's probably the only logical way, but just hoping someone might recognize something different to save me the work. Pulling homeruns would be ideal but that would involve pulling the underbelly cover on both sides and that would be "a bear". Disconnecting one wheel at a time would be a lot quicker.

The 4 magnets in parallel measured 1.1 ohms. One ohm plus or minus 0.2 ohms is considered normal. Of course this with trailer sitting still. My concern is that a magnet is breaking down during the braking process, maybe caused by heat.

time2roll wrote:

dryfly wrote:
Is it possible that the magnets could be breaking down internally under load of breaking??

Were the magnets replaced?

YES. See the OP. Complete new brake assemblies!

OK with new magnets I am thinking it is the wiring. Most likely the feed wires that go through the axles. Still could be anywhere. I would be inclined to pull new wire from the first splice and out to the brake magnets.

Unless somehow the wire in the drum assembly could be rubbing. PITN to pull them off and inspect.

Rest of the wire is fairly well protected.

As I learned even though the P3 is indicating a short, you still have brakes its just that one of the magnets, or wiring to it has an issue.

What an OP suggested to me and I did was jack up one wheel at a time and spin it, then have someone depress the brake, to locate the wheel. Once that is done and you find the wheel, check the wiring, looking for loose, worn rubbed. You can do a continuity check by connecting both sides to an ohm meter. I bought 50' roll of two conductor 16 gauge wire from the home center (lamp cord) and soldered on alligator clips. I stuck it in the appropriate hole on the 7 way plug then back to the wheel.

In my case the wires were fine, trailer ground was fine, and it turned out to be the magnet. The OP said if the wires are good just replace the magnet and that's what I did. Problem solved. I now always carry two sets of full brake assemblies with me as my brake problem occur hundreds of miles from home. I also carry wire. Never a good feeling being over the road with a problem. I hope that this helps you.

Happy trails