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

Question

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?

asked by: JAMES R

0

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.

expert reply by: Michael H

0

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Answer 1

There can be a very small amount of power on the brake output circuit of a 7-Way (5:00 position) which would be the brake controller checking for a trailer, but there should not be 12 volts of power. That indicates a short of some kind or a problem…

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Answer 2

Your brake controller should be getting 12 volts of power going into the brake controller. The wire that feeds power to the brake controller is the Black wire. You can test this wire by using a multimeter part #PT89ZR. The amount of power coming…

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Answer 3

On each individual electric brake magnet the amperage draw would be 3.0 to 3.2 max amps at 12 to 13 volts on 7-inch brake magnets and 3.2 to 4.0 max amps at 12 to 13 volts on 10 and 12-inch brake magnets. The max amperage draw for the brake magnets…

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Answer 4

If you are receiving no power at the receptacle but you are receiving power at the bumper 7 way connection then it is unlikely it is a blown fuse. More than likely it is a damaged wire or a bad connector, to determine this start by tracing the…

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Answer 5

All the brake controller needs to sense a trailer connection so that you can test it is a slight amperage draw on the output circuit. For that you can use a circuit tester like the part #PTW2993 with one pin grounded and the other on the output pin.…

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Answer 6

Since the trailer was off of the ground it would not take much voltage to stop the wheels from spinning so they may be getting power but they may not be getting enough power due to a short or wiring issue. But 9 times out of 10 weak trailer brakes…

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Answer 7

Since you are exceeding the trailer's gross vehicle weight rating (GVWR), the braking power is surely to be compromised. I would first recommend increasing the gain on your vehicle's brake controller. This will help to increase the braking…

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Answer 8

Since you are not getting the 12V power when your truck is running, you most likely don't have a fuse issue as you stated their isn't a specified fuse or relay in the owners manual. The issue is that your truck is computerized even at the…

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Answer 9

The AX (Auxiliary) location on the Hopkins 48505 connector that you reference, which is the same one used on the Hopkins #H20046, is typically used for 12V power. If you take a circuit tester like part #PTW2979 or #C73NR you should see that the…

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Answer 10

The only pin that should be continuously showing 12V power on the 7-Way connector on your vehicle is the 12V power circuit which is normally the black wire but not always. In 7-way wiring the 12V auxiliary power feed is carried on the contact at the…

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Answer 11

I would stick with the standard 12 volt circuit at the 1:00 position rather than use the center pin, which is normally used for reverse lights. Please note that the 12 volt circuit on a trailer connector, no matter which pin it is associated with,…

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Answer 12

Brakes can be installed on only one axle of a tandem axle trailer, however you should first check your state laws to see how many brakes are required for the gross vehicle weight rating (GVWR) of your tandem axle trailer. Some states require a…

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

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