trailor brake wiring

StudNuts

StudNuts

Well-Known Member
Joined
Mar 21, 2005
Location
Wendell
For some damn reason the brakes on my trailor quit working. when the truck brake is applied, the controller just gives and error. I tested the output from the truck and its all gravy. I checked all the wiring under the trailor, visually it seems ok. I found one questionable spot, but cut the wires and respliced to make sure. The ground is good. I took the wheels and hub off and the brake pads are like new, and the wiring in the hub seems good. Anyone to guess what could go wrong with my brakes. BTW, all the lights are functional. Just no brakes.
 
MAgnets????

The magnets were shot in my old trailer. You should here a buzzing at the brakes when the truck brakes are applied. Check the continunity of the lines.

You did install a controller in the truck right? :flipoff2:
 
I have a SuperDuty, of course I have a brake controller.


But would the magnets cause the brake controller to throw error codes?
 
StudNuts said:
I have a SuperDuty, of course I have a brake controller.
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I've actually seen a SuperDuty without so much as a trailer hitch... :rolleyes:

Anyway, when I just went through my trailer's brakes - the wiring that went across the axle tube went in through a grommet, through the inside of the axle tube, and out the other side.. yeah, right. Cut that wire, and ran new lengths on the outside. Someone else had mentioned to me (Yager I think) that where the wiring enters the axle tube is a source of shorts, and I can clearly understand that!

Sounds to me like something finally rubbed through...
 
Yeah, it seems like an error code would have to be from the brake wire being grounded.

Oh and a buddy of mine (very educated) bought a 2002 Superduty and though that the break controller was factory and part of the dash like the new 2005's are. I had to brake the news that he needed a controller.
 
Well, Im going to buy some wire and rewire the damn thing. If that dont work, ill buy new magnets. If that dont work, im going to buy a new trailor - im in need of a goosneck anyway ;)

Ill try the axle tube wiring. That was actually the first thing I thought of, but the grommets and the wire look in great shape, so I let it ride. Get the snips and start cutting I guess.

I had to brake the news that he needed a controller.
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Im not that dumb.
 
Magnets are much easier to replace then re-wireing the whole trailer Jon. Just pull your drums and see what your magnets look like.
 
when i had a magnet going out my controler (prodogy) was going open, short and NC and all other kinds of errors. I ran 2 seperate runs down each side of the trailer and eliminated the wireing across the tubes.. It really doenst take much to cause a short... Also make sure you have a good trailer ground to the plug, so your not just grounding through the ball..

fwiw: usually you can't 'see' that a magnet is bad you really need to test it.. Mine were like 3 ohm when good, the bad one was in the 50s.. by runnign individual runs the to front I can now test all that without crawling under the trailer...
 
Anyone know how much amperage 4 brakes can draw? I guessed at 15.. Want to make sure I didn't undersize the wire on mine.

I'm gonna just replace all 4 brakes & magnets in a week or 2, they're still not working like I want... (grease got onto the brake shoes from the previous owner)
 
Rich said:
Anyone know how much amperage 4 brakes can draw? I guessed at 15.. Want to make sure I didn't undersize the wire on mine.

I'm gonna just replace all 4 brakes & magnets in a week or 2, they're still not working like I want... (grease got onto the brake shoes from the previous owner)
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I(current) = V(voltage)/R(resistance)

So if each brake coil has 3 ohms of resistance on a 12 volt system (actually about 13.4 volts), that would be 13.4/3 = 4.46 amp per coil, x4 would be 17.84.
I would allow for safety, 25% above expected draw, so in that case about 22 amps. Remember if for some reason the voltage drops, the current will go up.

So measure the resistance across the coil to get an accurate measurement.

Hope this helps.
 
I got the hubs all apart now and I am going to test the resistance of the magnets and hopefully troubleshoot the cause. Im still convinced its a wiring issue. They worked last weekend when I went to URE and now the just quit working. When in tow, speratically they will work, the rest of time just throw an error code on the controller.
 
well, i checked the continuity - 006 on drivers side, 007 on pass side. So magnets check out. The lights and brakes share a common ground, and the lights work so its not the ground. I got fed up and just rewired the brakes and now they work. I inspected the wires and there are not tears/cuts whatso ever. I dont understand why, but they work now :)
 
StudNuts said:
well, i checked the continuity - 006 on drivers side, 007 on pass side. So magnets check out. The lights and brakes share a common ground, and the lights work so its not the ground. I got fed up and just rewired the brakes and now they work. I inspected the wires and there are not tears/cuts whatso ever. I dont understand why, but they work now :)
Click to expand...

Wires can break internally and you would never see it. Use a high strand count wire (automotive) so the wire flexes easier. The more flex a wire has the longer it will last.
 
Rich said:
Anyone know how much amperage 4 brakes can draw? I guessed at 15.. Want to make sure I didn't undersize the wire on mine.
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Per Dexter's site - 3 amps per brake.
 
StudNuts said:
Well, Im going to buy some wire and rewire the damn thing. If that dont work, ill buy new magnets. If that dont work, im going to buy a new trailor - im in need of a goosneck anyway ;)

Ill try the axle tube wiring. That was actually the first thing I thought of, but the grommets and the wire look in great shape, so I let it ride. Get the snips and start cutting I guess.


Im not that dumb.
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I know where a 32' gooseneck is. It may be for sale soon. PM me if you need contact information.
 
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