Electric Trailer Brakes Lock Up When Trailer is Plugged in to Tow Vehicle

Question

Question:

Hi, my 10x2.25 electric brakes will not release when the 7 way plug is plunged into my truck.My trucks pulls my friends trailer with out problems so I am guessing that the problem is in the trailer.Also the break away is bypassed so that is not it.My controller is a voyager model if that helps.I really appreciate any help or suggestions.

asked by: Dale C

0

Expert Reply:

The easiest first step here would be to try the trailer on a different truck, and see if the same problem occurs. If the trailer brakes are free until the trailer is plugged in, I suspect that something is mis wired. I would suggest examine the wiring where the break away system was bypassed and make sure that the 12-volt accessory feed is not connected to the brake wire at some point.

Are you by chance using a 7 to 6-way adapter? If so, there are two accepted ways of wiring a 6-way connector. One method uses the center pin as the brake output circuit, the other uses the center pin as the 12-volt accessory circuit. If the trailer is wired one way and the adapter the other, the brakes will receive 12-volts as soon as the trailer is plugged in. We offer a universal 7 to 6-way adapter, part # 47549 that can be wired either way which would solve that problem for you.

expert reply by: Mike L

0

Gary H.

4/22/2020

I am having the same issue with my dump trailer. I have had this trailer for several years. I am still using the same tow vehicle. As soon as I plug in to my vehicle the brakes lock up. I tried plugging it into another vehicle and the same thing happens.

Reply

Chris R.

4/24/2020

So we know the problem is on the trailer and it's also not a standard mis-wire, since it's a new issue on an old trailer. What's likely happening is that the brake output wire is shorting out to the frame or a neighboring wire somewhere down the line. I recommend starting at the trailer side connector and visually inspecting it for any corrosion that might be bridging a couple pins together - cleaning out as needed. From there it's really just a matter of trying to trace the brake output wire back to the brake assemblies, looking for any frayed/exposed sections that need to be replaced.

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Gary H.

4/25/2020

I couldn’t find anything wrong with the wiring. I replaced the battery in the trailer and the problem went away.

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Chris R.

4/27/2020

That is odd, but at least the issue is fixed! Please let me know if anything like that pops up again.

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See All (6) Replies to Gary H. ∨

Adrienne

4/28/2024

I have this problem. Can the plug be re wired at home? Would love to talk to you about this. Please call 509-432-4572.

Reply

Mike L.

4/30/2024

@Adrienne If you're using the Hopkins # 47549, it can easily be disassembled and the wires swapped. If you're using a different brand adapter, You'll need to disassemble it by removing the screws on the side of the adapter. Once you get it open, check to see how the wires connect to the terminals. If they're soldered, you CAN swap them, but it's pretty difficult to do so and you'd likely be better off going with the # 47549. If they're attached with screws, swapping the wires will be simple. Please let us know if you have further questions!

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Jeremy T.

9/28/2025

This may not help anyone, but just in case...I had this same issue today. Hooked up my trailer today and when I went to pull away, the rear axle brakes were locked up. After reading the replies on here I started tracing back through the electrical system. I eventually found that I had plugged the trailer plug into my truck upside down... somehow. Ha! Guess that crossed up the connectors.

Reply

Plug S.

2/2/2026

@JeremyT lol life saver. Worked for me .

Reply

Answer 1

There are a few things that can cause the brakes to lock up on a trailer. First, disconnect the trailer from the vehicle. Then use a circuit tester like #PTW2979 if needed to test the connector on the vehicle. Have someone sit in the truck and run…

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Answer 2

I have a suspicion about what might be causing the problem you mention. Do your trucks have 6-way trailer connectors? Or, do the trucks have 7-way connectors, but you are using a 6-way to 7-way adapters because the trailers use 6-way connectors?…

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Answer 3

The Taskmaster tire #TTWPRG235R16 and most of all special trailer tires are manufactured by a couple companies that are based in China. The tire must meet the same DOT specifications for tires to be sold in the USA.

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Answer 4

For a tandem axle trailer rated for 7000 lbs, you can use either a Load Range C or D tire. Each axle will be rated for 3500 lbs so you need a tire that will carry 1/2 that capacity. That would make your minimum load range before limiting your system…

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Answer 5

The easiest way to disconnect your trailer brake controller from your vehicle is to disconnect your brake controller. You'll just need to unplug the controller plug from the back of the brake controller. This should eliminate any power draw from…

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Answer 6

The 14" aluminum wheel used for the Westlake ST205/75R14 Radial Tire w 14" Condor Aluminum Wheel - 5 on 4-1/2 - LR D - Gunmetal #LH37VR is compatible with 1/2"-20 lug nuts like #LHLR103. For this stud size you will want to torque the…

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Answer 7

There are 4 potential problems that are stated in the instructions that could cause the n.c. (no connection) reading on your Prodigy P2, part #90885. I am including a link to the instructions for the Prodigy P2 brake controller. The 4 possible causes…

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Answer 8

Since wire color codes are NOT universal, we always recommend wiring by function, rather than wire color. If you look at the Trailer Wiring FAQ article I have linked you to, you can see some diagrams showing the proper way to wire a vehicle and…

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Answer 9

For a 12,000 lb. electric car trailer winch like the Bulldog Winch Trailer Winch part #BDW10040, I recommend a standard 12 volt lead acid battery rated up to at least 650 cold cranking amps (CCA). As long as the battery is rated up to 650 CCA then…

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Answer 10

The port for installing the brake controller is located in a junction box behind the emergency brake pedal. Remove the black lid from the junction box, the brake control adapter is plugged into the second slot from the left on the top row. If you…

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Answer 11

On the 2009 Chevy Silverado there is no port to plug in a brake controller. Instead GM put a tow package wire bundle under the dash. You would use the harness with the blunt cut wires that comes with the brake controller and splice into the tow…

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Answer 12

Usually when electric trailer brakes lock up it is because the brake pin on the trailer side connector is getting constant power. If you are using a 6-Way trailer connector or a 7-Way to 6-Way adapter then the likely cause is that the 12 volt circuit…

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Electric Trailer Brakes Lock Up When Trailer is Plugged in to Tow Vehicle

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