Electric Trailer Brakes

tac911t

tac911t

New member
I am working through an electical problem with my trailer brakes.

When I hookup the battery for the brakeaway, with the brakeway switch open (plug inserted), I get sparks from the wire I am connecting to the battery, the trailer brakes kick on, and my brake controller in the tow vehicle displays the light that indicates a wiring problem.

I last used the trailer in early May, and each time I use the trailer I check the breakaway system to ensure it works (it did in May). The other week (without testing the system) I put the breakaway battery on a battery charger overnight without disconnecting the trailer wiring to the battery, but I did leave the breakaway switch plug inserted, which I would think disconnected the battery from the trailer wiring.

When I hooked up the trailer to the tow vehicle and pulled the plug on the breakaway switch, my brake controller started smoking and fried itself.

After running over to Walmart and purchasing a new brake controller (one with a light that will light up when it senses a wiring short, and has built-in short protection) and a new battery (small lawn mower battery) and installing all the new parts, the trailer brakes act the same, they kick on as soon as I connect the new battery, and now the brake controller displays the light that indicates a wiring short.

I cut one of the wires to the breakaway switch, same thing, brakes kick on and wiring short light is on.

With the breakaway battery disconnected, the trailer brakes work fine with the brake controller.

Any ideas on where the problem may be? Could it be a bad brake magnet?

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Todd Cohen
ITB Nissan 200SX
 
You've got a polarity problem somewhere - and you're got a ground where a + should be.

The magnets in the some trailer wheel brake lever arms are electrically 'floating' above trailer ground, so the two wires going to them should not be grounded. You may be picking up a ground somewhere in this wiring, and when you hook up the break-away battery, you're hooking the + battery to the chassis ground...hence all the smoke.

You need to trace all the wiring to the trailer brakes out, see how they're wired ('floating ground' magnets, etc.) and make sure you don't have a wire reversed someplace. All it takes is one wire backwards, and you're likely to get the symptoms you described.

Trailer wiring is a pox on humanity. The damn things come from the factory with bad bulbs, screwed up brakes and crossed wires, and it only gets worse after that. I have a serious hatred of trailer manufacturers.

[This message has been edited by JohnRW (edited July 28, 2005).]
 
Originally posted by JohnRW:

Trailer wiring is a pox on humanity......

[This message has been edited by JohnRW (edited July 28, 2005).]
Click to expand...

Bwaaahhaaa!

THAT is SO true!

It never ceases to amaze me how much time is spent dorking with the simplest of systems! Trailer wiring is 1st grade stuff, but it is always FUBR.

And if you are the second or third owner, God help you...splices, mismatched colors, loose wire nuts, corrosion, pinched wires, chaffed wires...it's all there........ in ONE trailer!

Reminds me...I have to go re-light/re-wire my enclosed!



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Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]
 
Um, are you supposed to check the breakaway battery with the trailer wiring hooked to the tow vehicle? I could be totally wrong, but I seem to recall a decal on my breakaway saying to check the breakaway before hooking up.

What caused you to replace the battery?
What about the breakaway switch? You replaced everything but, and things work fine when you isolate the breakaway circuit.

Maybe the charging fried the breakaway switch?

Let us know what you find.
Guess I've been lucky with my trailer lights and brakes, both trailers worked fine from new, although I do think something's not working with the interior 12v lighting on my enclosed. Yeah, guess that would be asking for too much :-)

Michael
 
I was able to fix the problem. I replaced the two wires from the breakaway battery; the insulation on one of the wires did look like it had degraded.

I have always checked the breakaway with the trailer hooked up to the tow vehicle, it does not seem to matter, connected or not, once I pull the plug on the breakaway switch the brakes activate.

Since my old brake controller fried itself, I though the battery may have had a short in it that was causing the problem. The old battery was fine.

These two wires cost $150 to fix, $100 for the brake controller and new battery, and $50 last night at Northern Tool for wire connectors, crimping tool, and I don’t know what else. Since I was already into this problem for $100, I need to ask for advice (which I got), before I began replacing brake magnets and wiring buried underneath the trailer.

I am at least the 2nd owner of this home built trailer. I think it cost me about $100 last year to get the trailer ready for the state inspection. This year I though I was on top of the trailers maintenance, everything worked several months ago, even after the trailer sat all winter.


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Todd Cohen
ITB Nissan 200SX
 
Todd,

If you want the trailer to never have another problem, go to radio shed, and get a cheap VOM meter. $25 is about the least you should pay. It's a really handy tool that will tell you how many AAC or DC volts you have, and whether the wires are grounded, etc. Super simple to use and will save a hundred troubleshooting hours.

Also, get some wire loom and wrap the exposed wires in it where they could chaf and ground...the wire quality aint the best on some trailers, and sunlight can kill the insulation.

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Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]
 
Jake,

Thanks for the advice. I have a VOM meter, not sure how to use all the features; mostly I use it to check for voltage. I probably should read up on using it to check for resistance.

Interesting about the trailer wires and sunlight, I never thought about that.



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Todd Cohen
ITB Nissan 200SX
 
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