Shorting electric brakes

[John in Michigan]

Mark, your brake controller is indicating a short, thus 1 ohm resistance. So if you have completely isolated the wiring from the frame, then next things I would check:

- check 7 blade plugs to make sure none of the wires are touching/loose/etc
- inspect both brakes and test the resistance of the brake magnet (should be significantly higher than 1 ohm)

[John in Santa Cruz]

typical electric brake is 3.0 to 4.0 ohms. at 12 volts, that draws 12/3 = 4 amps to 12/4 = 3 amps. (ohms law, volts/ohms = amps).

[Kevin A]

May not help but...

We had an intermittent short indicated on our Prodigy controller when towing last Sept. It would be green and fine, then suddenly red with the screen warning. After checking everything (I thought), I reached behind the wheels again to see if anything was loose. One insulated connector seemed to wiggle a bit when I gently pulled on the two wires entering it. My wife, watching the controller screen, noted it would flip from green to red and back as I wiggled it. My problem was found! I replaced the connection and insulation and everything has been fine since. Lesson: the connection looked fine but it was moving with the action of towing it, causing the broken circuit.

[John in Santa Cruz]

That sounds like an open circuit, not a short?

[Kevin A]

True, but the error message simply indicated brakes not working/connected. Could have been either condition of short or break.

[John in Michigan]

Original poster's initial post states that the brake controller indicated a short.

[Kevin A]

You are correct. That's why I started with "This may not help but..." My error message was "Open ground/No brakes."

[Byron Kinnaman]

Originally Posted by John in Santa Cruz

That sounds like an open circuit, not a short?

Everybody knows that there's only two problems with electrical circuits, a faulty ground and a short.

[steve dunham]

Disconnect both wires a both brakes and then ohm out the wire from the 7 pin trailer plug back to the brakes If the wire ring clear ( No short to ground )
Then check the blue wire for continuity from the 7 pin plug to the brake
That should tell you where the problem lies

[Radar1]

Originally Posted by Paul O.

The electromagnet can become worn and eventually the coil will short to the drum when applied. That in turn will short to the spindle and frame through the bearings. This will be intermittent and the brake behavior will be erratic. I had tat problem and it was a pain to diagnose. I ended up buying new brake assemblies (with self adjustment - well worth it).

Same with me. On a long trip I started getting a " not connected" warning shortly after applying brakes. Pulled my hubs, the magnets were worn, so I put in complete self adjusting brake assemblies and love them. Doesn't matter which wire is which, as long as one is grounded and the other gets power.

[Markz]

ADDITIONAL CLUES!

With the camper unhitched the brake controller switches between connected and not connected. When I apply the brakes it shows SHORT.

[Markz]

Originally Posted by John in Michigan

Original poster's initial post states that the brake controller indicated a short.

New Clues!

With the trailer not connected, nothing in tow. The brake controller toggles between connected and not connected. When I apply the brakes the controller shows Short.

I'll check the seven pin on the truck. Othwise I have no idea.

[John in Santa Cruz]

so its showing SHORT without a trailer plugged in? then for sure, the problem is truck side.

follow the harness from the brake controller, there should be a plug somewhere behind/under the dash near the left side where the brake controller harness plugs into the vehicle harness, unplug this connector, and try again, if THAT shows short, then the problem is in the brake controller harness, or the controller itself..

otherwise, check the back of the truck's 7-blade tow socket, check the cable bundle which probably goes from the 7-blade connector forward to the drivers side of the cab and into whatever sort of electrical junction box your truck has under the dash... specifically inspect the cable where its secured to the frame rails, and near any suspension parts or anything else that might move or flex.

[Markz]

Thanks, I'll give it a try and let you know.



BTW the brake controller is a:
Tekonsha Prodigy P2 Trailer Brake Controller - 1 to 4 Axles - Proportional and the tow vehicle is a Chevy Traverse.

Originally Posted by John in Santa Cruz

so its showing SHORT without a trailer plugged in? then for sure, the problem is truck side.

follow the harness from the brake controller, there should be a plug somewhere behind/under the dash near the left side where the brake controller harness plugs into the vehicle harness, unplug this connector, and try again, if THAT shows short, then the problem is in the brake controller harness, or the controller itself..

otherwise, check the back of the truck's 7-blade tow socket, check the cable bundle which probably goes from the 7-blade connector forward to the drivers side of the cab and into whatever sort of electrical junction box your truck has under the dash... specifically inspect the cable where its secured to the frame rails, and near any suspension parts or anything else that might move or flex.

[John in Santa Cruz]

ooops,, hahahaha, with the brake controller harness unplugged, duh, its not going to show anything, as it won't be getting any power.

ok, how about this... with the vehicle shut off, ohm the truck's trailer connector brake pin to ground pin. this should be like 1 ohm or more. if its close to zero ohms (or, say, less than about 0.2 ohms), something is shorted all right... now unplug the brake controller harness connector under the dash, and do this again. if its now 'open circuit', the problem is in the brake controller or the pigtail/harness that its plugged into. if with the brake controller harness unplugged, you still see less than 0.2 ohms, then the short is in the chassis wiring somewhere, inspect the harness under the truck, follow it up to where it goes into the cab looking for abraded sheathing or whatever.

[Markz]

Originally Posted by John in Santa Cruz

ooops,, hahahaha, with the brake controller harness unplugged, duh, its not going to show anything, as it won't be getting any power.

ok, how about this... with the vehicle shut off, ohm the truck's trailer connector brake pin to ground pin. this should be like 1 ohm or more. if its close to zero ohms (or, say, less than about 0.2 ohms), something is shorted all right... now unplug the brake controller harness connector under the dash, and do this again. if its now 'open circuit', the problem is in the brake controller or the pigtail/harness that its plugged into. if with the brake controller harness unplugged, you still see less than 0.2 ohms, then the short is in the chassis wiring somewhere, inspect the harness under the truck, follow it up to where it goes into the cab looking for abraded sheathing or whatever.

Love these instructions! It may take me a bit to get to this but I will post here as soon as I follow through. Thanks [emoji3]

[Markz]

Found the Short! Loose wire harness allowed the wire to rest on the muffler and burned through the insulation.

On to the next repair! [emoji2]

Sent from my SM-G930V using Fiberglass RV mobile app

[Markz]

Thank you everyone for your help!

Sent from my SM-G930V using Fiberglass RV mobile app

[Paul O.]

Thanks for posting about the outcome of your search.

[Markz]

Happy there wasn't more damage

I repaired the wires and secured the wire harness out of the way with zip ties.

The brake controller no longer shows a short and appropriately displays "not connected" without the trailer.