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2 New Electric Trailer Brakes Get Full Voltage But with Other 2 Connected Voltage Drops Low  

Question:

my 20 ft. RV has new brakes. They dont work. Ive undone the connectors at the trailer tongue, established 14vdc, redid the connections and went back to the first axle, did the same, and continued to the rear axle and did the same so i now have 13-14 vdc at one side of each axle as Ive eliminated the other side till i figure this out. I did discover a bared wire entering one axle but ive eliminated that for now. so............ I have good voltage at the hub since ive duct taped the trailer control to full on ............NOW THEN i can hook the white gnd wire to one lead of either new magnet and still have 13-14 vdc but as soon as I touch the other lead to the blue hot wire the voltage s to about a tenth of a volt or pretty much zero and neither wheel will stop turning.......... new brakes, new magnets, good install, two wheels tested, brakes up touching the drum. new controller................ what the hay?

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Expert Reply:

The issue sounds like it is in the wiring going from one side to the other side. First, you may need to switch to a larger gauge wire such as # 10-1-1. But given how you have been testing and the results you are seeing there should not be that much voltage drop even with a smaller gauge wire. So wire gauge would be just part of the problem.

Check for any pinched or damaged wires and fix as needed. If you have a breakaway system then inspect that wiring as well.

It could also be how the wires are ran to the brake magnets. There should be one wire coming back that will split with one end going to the right side and the other going to the left side. The magnet power wires will splice into the power wire running to their side of the trailer. I have included a picture that shows this.

As far as the grounds make sure they are connected to clean and corrosion free bare metal surfaces near the magnets. You may have to sand any paint or covering at the ground location to get a solid ground connection. Also make sure that the vehicle and trailer side connectors are clean and free of corrosion.

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