Low Voltage to Trailer Brakes After Installing New Brake Assemblies

Question

Question:

I have been reading some others posts but i cant seem to find what I am looking for. I just put on all new trailer breaks all the way around. Backing plate and all. But I still have very weak brakes. They are 12 in brakes on 6k axles. Now when I measure my trailer connector I am only showing 10 volts when I slide my controller and it turned all the way up. Also when I measure on my trailer side of the connection I get an even less 8 volts. Where is my problem coming from. I am losing power the further back I go. Thanks

asked by: Tyler

0

Expert Reply:

Its not uncommon for there to be slight voltage drop off over a certain distance but with the brake controller set to the maximum you should still be getting 12 volts at the brake magnets.

We need to determine if the low voltage is coming from the controller or somewhere down stream. What you will do is sever the brake controller blue wire several inched back from the controller. Then use your meter to test for voltage on the end of the blue wire coming from the controller while applying the manual override on full.

You should be getting 12 to 14 volts at maximum output. If you are getting less, fluctuations, or nothing then there is something wrong with the controller and it will need to be replaced.

If everything checks out fine at the controller then reconnect the blue wire. Next make sure the vehicle and trailer side connectors are clean and free of corrosion inside and out. On the vehicle, inspect the wiring as far as you can and fix any damaged areas.

On the trailer make sure no wires are pinched or damage and that the grounds are attached to clean and corrosion free bare metal surfaces. If you still get low voltage at the vehicle connector then there must be a wiring issue somewhere that you can't get to.

You could bypass the brake output wire by severing the brake controller blue wire and attaching a different wire, # 10-1-1 (sold by the foot) and routing it back to the trailer connector manually. If you do this be sure to avoid areas that may pinch or burn the wire.

expert reply by: Michael H

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Answer 1

If you are only getting 1.5 volts at your brakes then there is an issue, but there is not a fuse that controls the brakes. There are a number of possible issues so you will need to find out if the issue is on the brake controller, truck, or…

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Answer 2

It depends on what the brake controller output is set to. If you have the brake controller set to the maximum then there should be about 12 volts at the brake magnets. To see if the brake magnets are drawing the correct power set the brake…

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Answer 3

I believe you almost solved the problem when you swapped the wiring, but in reality you needed to use 10 gauge wire like part #10-1-1 (sold by the foot). You are experiencing a voltage drop due to the long distance of wire that's not thick…

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Answer 4

Testing your trailer brakes for proper function on the test bench will require a multimeter that can display readings for both amps and ohms, such as part # PT89ZR. (Some brake controllers, such as the Tekonsha P3, have built-in test functions.) You…

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Answer 5

It should be getting close to 12 volts if the power output is set to the maximum on the brake controller. Some brake controllers will not work properly if they are titled or turned to the side or if it has a leveler knob that is not level. Check…

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Answer 6

First, do a visual inspection. You should make sure that the front of the magnet is not worn to the point where the interior copper windings are visible. Also, check the armature surface (inside rear of brake drum where magnet rides) is free of…

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Answer 7

I do not recommend that you bypass the break away system because in many states it is a requirement to have a working break away system. Trailer brake magnets will have one power wire and one ground. The power output from a break away system will go…

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Answer 8

Yes. There should always be a very light power on your brake controller wire. However, it should be extremely minimal. As you increase in power using the manual override, you should see an incandescent circuit tester like #PTW2993 going from almost…

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Answer 9

The first test you will want to do is to test the amperage of the trailer braking system with a multimeter, like #PT89ZR. First, you will connect the ammeter inline with the blue wire exiting the back of the brake controller. Check the amperage. If…

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Answer 10

A slight voltage drop between the controller and the magnets is normal. But you will need around 12 volts at the magnets for proper operation. The only way to know the wire gauge is to strip away the insulation and measure just he copper strands. If…

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Answer 11

If you are only getting the 8 volts when you pull the pin using a meter like #PT89ZR, that has nothing to do with your brake controller as the breakaway battery is powering that from the trailer itself. You can confirm your brake controller is…

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Answer 12

Since you are getting 12 volts at the trailer connector and at each magnet individually it sounds like there is possibly a short between some of the brake magnets or, since you have 6 brake assemblies, maybe you are not using a wire that is thick…

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