Brake Wiring Warning

slaytop

Well-known member
I wanted to post this warning because it has the potential to be a problem for any trailer with brake wires routed through the axle tubes.

My Landmark had the brake wires routed through the axle tubes from the power source on the left side to the brakes on the right. The wires were similar to 18 gauge lamp cord with standard insulation. The wires passed through a grommet at each end of the axle tube and then laid freely within the axle tube. It makes a neat looking package with the wires out of view.

The problem is with the wires inside the axle freely moving as the axle vibrates during travel. Since the wires are not perfectly flat and have some bends in them, the insulation will wear slowly at the points where a bend makes contact with the axle tube. Eventually the insulation will be worn through and the bare wire will make contact with the axle tube. That will cause a short, blow a fuse and cause the brakes to fail.

At first, when the wire makes its first contact it is a very tiny area and may cause a momentary failure or warning and then as the wire moves a bit the brakes will go back to a normal mode. It will get worse as more of the insulation wears away.

My brake controller gave me a warning message that there was a problem. I checked all the external wiring and it looked fine. Since I had this same problem on a previous TT, I pulled the wires out of the axle tubes and found one of the wires to be worn through and the other beginning to do the same. In addition, the wire that was worn was lying in water inside the axle.

I have attached two photos of the wire so readers can get the idea of what I am saying. Sorry I couldn't focus the camera any better at the close range.

I replaced the wire with heavily insulated 18 gauge wire and attached it to the outside of the axle tubes with nylon straps.

One other idea that I like is to have a 30 Amp. self-resetting circuit breaker in the brake line rather than a fuse in the event of a short of this nature.
 

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slaytop

Well-known member
I want to add to this string to include another brake wiring problem that can also shut down the electric brakes unexpectedly.

I have Al-Ko brakes on my Landmark. This post may only apply to this brand of brakes but it is worth noting.

The electric brakes include a magnet assembly that includes a lever and a magnet mounted on the end. The brake magnet wires are clipped to the lever in two places and are firmly kept in place while traveling. The magnet itself has a little slack and is able to move on the end of the lever. As the wires leave the magnet they are wrapped around a short leg (that holds the lever away from the backing plate) before reaching the first clip. Since the magnet has some movement and the wires move with the magnet before reaching the lever, it is possible that abrasion and/or tension will cause the insulation to wear down at the point the wires touch the leg on the lever.

I found wires of two of the four brakes on my Landmark to be worn completely through the insulation where they wrapped around the edge of the leg on the lever.

Rather than replace the magnets, I found it satisfactory to repair the worn insulation with liquid plastic tape and heat shrink tubing. The heat shrink tubing will provide additional abrasion and wear resistance.
Larry
 

davelinde

Well-known member
Good note. I have a Prodigy brake controller and instead of letting the fuse blow the Prodigy will shut off the brakes and display a code for "short" or "overload" depending on how bad the chafing has become. In my case the problem only happened in heavy rains after an hour or so and I finally traced it to the wiring in the axles.
 
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