peculiar brake situation with Prodigy P3

[rexlion]

The short version: My Prodigy P3 is displaying "OVERLOAD - NO BRAKES", but the trailer brakes are still activating. What's the most likely cause, and should I worry?

The long version: I hooked up to the trailer on Monday and checked/adjusted the brake controller. It was working normally. Tuesday and Wednesday I was towing (not long distances) but had no occasion to look at the controller, so I can't swear that it was still working as expected. On Wednesday I dropped off the trailer at a shop to have a new axle and springs installed.

When I hooked up the trailer at the shop on Thursday and started down the street, at the light I noticed that the P3 was displaying the warning message "OVERLOAD - NO BRAKES". So I turned around and took the trailer back to the shop. They put a tester on the 7-pin receptacle (back of the vehicle while standing still) and got a proper reading, so it looked to be the trailer. I left it with them again. They went through the brakes "thoroughly" (their word) and everything checked out; they said they could not find any bad grounds and the brakes functioned fine. I hooked up and pulled forward a bit, hit the brakes and the P3 showed the fault. When I asked if we could try the tester on the back of the vehicle one more time, the guy acted put out and said I'd have to take my vehicle to a shop and have it checked out because they don't work on vehicles.

On the way home, I observed that the trailer brakes are activating as expected even while the warning message is displayed. If the vehicle is not in motion and I depress the brake pedal or use the controller lever, the P3 does not show a fault; only when I'm moving the rig forward will it fault.

With power set at 12.0, some numbers from the troubleshooting menu:
Battery 13.6V
Stoplight 12.8V
Output voltage 11.9V
Output current 5.6A
The above numbers were read while activating the lever.

I cleaned the 7-pin connection with Deoxit Red, and no change in behavior.

What is the likely cause? Should I throw some money at a new brake controller and see what results? Should I assume that the shop has screwed something up and can't find their mistake? Or something else? Since the trailer brakes are functioning, should I just let it go?

[hussbuss]

Had a similar problem with my last T.T. Had it in the shop for 4 new backing plates and bearing repack. Got it back and everything seamed alright until going to Florida from Wisconsin I lost breaking on 1 side coming down Mt. Eagle. Scary, it would pull to one side. Lucky I had a dually to keep it straight. Found out that when the shop put the new backing plates on a magnet wire got pinched between the plate and the axle flange. Didn't show up until hard braking. Look for anything like this. Also get rid of the scotch locks. Do it right with the proper connections. Good Luck and Happy Camping.

[opnspaces]

The problem is definitely in the trailer. You're controller didn't just decide to fail between the time you dropped off and picked up the trailer. Hopefully though the problem didn't now damage your Prodigy.

What I would do, but then I always do things a bit differently than most. Disconnect one wheel at a time and carefully do a test pull to see if the problem goes away. If the problem does go away then take it back and tell them which wheel seems to be causing a problem.

[bgum]

Dead short at or near magnet. Take it back to shop and have them fix their connections properly. It is not your controller. The problem started with them.

[rexlion]

10 years and probably 150,000 miles old. I'll do my best to shine a light into the square tube that some of the wire passes through; could be a wear spot like you say. One of the things I've been wondering is, what if the axle came with the wire that runs through it, and what if that wire had spot that isn't insulated? It would explain the commencement of the problem with the new axle.

[time2roll]

12 volts divided by 2.3 ohms gives 5.22 amps. Seems about right.

Double check the wiring is not rubbing some place and the connections are good. How old is this trailer?
Does seem like it could be something intermittent such as worn insulation in a blind area.

[rexlion]

Inertia! I hadn't thought of that. Thanks, that explains the difference in behavior.

Looking underneath, I see that the shop used quick splice connectors, the ones where you press the blade down to cut the insulation. Just waiting to corrode! 😞

[Terryallan]

rexlion wrote:
Ok, thanks, I guess the P3's reading of 5.6A tells me it is in range overall, right?

Both magnets are actuating (it's a single axle). I checked with a compass, for what that's worth.

If 2.3 ohms is excessive, that seems to indicate that the shop messed something up. But since the brakes work, does it matter? Maybe I should just ignore the warning message.

However, if 2.3 ohms is an acceptable readout, then I'd be inclined to think maybe the controller is bad.

I'm thinking it does not show a fault while sitting still, is because the controler is not doing any thing. Why? Because the P3 is a enertia based controler. When sitting still it is waiting for a signal. Pressing the brake pedal while sitting still will not send a current to the trailer. Activating the lever will. But only the amount of current you have dialed into the controler.

and since it worked as advertised before they worked on it. I would say something did not get hooked back up correctly.

[rexlion]

Ok, thanks, I guess the P3's reading of 5.6A tells me it is in range overall, right?

Both magnets are actuating (it's a single axle). I checked with a compass, for what that's worth.

If 2.3 ohms is excessive, that seems to indicate that the shop messed something up. But since the brakes work, does it matter? Maybe I should just ignore the warning message.

However, if 2.3 ohms is an acceptable readout, then I'd be inclined to think maybe the controller is bad.

[time2roll]

At full braking you should have about 3 amps per wheel.

[rexlion]

Bookumdanno wrote:
You have a short somewhere in your brake wiring or a magnet in the drums. You need to ohm the electric brake connector to ground at the 7 pin trailer connector. Should have around 1-2 ohms. If higher you need to go thru the wiring and then to each wheel and check each individual magnet for 3.2-3.5 ohms. If all this is good then look at the Controller.

Thanks, I just checked the plug and got 2.3 ohms. Is that in the proper neighborhood, or too high?

[Bookumdanno]

You have a short somewhere in your brake wiring or a magnet in the drums. You need to ohm the electric brake connector to ground at the 7 pin trailer connector. Should have around 1-2 ohms. If higher you need to go thru the wiring and then to each wheel and check each individual magnet for 3.2-3.5 ohms. If all this is good then look at the Controller.