Fixing Weak Trailer Brakes on 2025 Ford F250 with Redarc Tow-Pro Liberty Installation

Question

Question:

My issue. I have a new 2025 f250 diesel with factory installed trailer brakes system and the trailer brakes are very weak with all the setting set to max. My 2020 f250 had no problem with stopping my goose neck trailer at gain 7. total wight about 10k. My goose neck is one year old and I have a new 18 ft trailer and both have the same weak trailer brakes. My buddy towing the 18ft trailer with his f150 has no problem. I have had my 2025 f250 into the dealer at least 7 times for this problem with no results. Last Thursday they put under recall an updated trailer brake controller and still not working properly. Maybe about a 10 gain in braking. But still Weak trailer brakes. Its not a trailer problem. At this point I am on my own to fix the problem and want to know how your system will hook up to the factory wiring and will it bypass the factory system. I have done a lot of testing with a volt meter and I am getting about 3 to 4 volts at the trailer plug and at the brake controller about the same put for a short burst to about 5 volts. This is with the gain at 10. This seems low to me. How and where dose your plug adapter hook to the factory wiring plug. Do I unplug one of the two plugs going to the factory brake controller. There is also a plug next to the brake controller with 4 wires including the blue wire that I get voltage from when applying the brakes. This plug is not plugged into any thing. Before I spend $350 on your brake controller on my brand new truck I need some answers. Do you think your controller will solve my issue. Thanks for your help Larry

asked by: Larry O

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BC
(click to enlarge)

Expert Reply:

Hi Larry, I can definitely understand your frustration, and based on your testing, that low voltage at the 7-way is not normal and does point to an issue on the truck side rather than the trailers. Also, thank you for your photo.

The good news is you do have the correct factory plug under the dash to make an aftermarket controller a clean install. That gray connector in your photo is the factory brake controller port, so a plug and play setup like the Redarc Tow-Pro Trail Brake Controller with the custom harness part # RED44UR will connect directly there without any cutting or guesswork. This allows the Redarc to take over the brake output signal and send the proper voltage to your trailer brakes.

Instead of increasing power beyond normal, what the Redarc will do is restore proper, consistent output that your factory controller is not providing right now. That is why setups like this often feel like a big improvement in braking performance when the factory system is underperforming.

You will not need to unplug the factory controller module itself, the Redarc simply uses that port and manages the signal through the truck’s wiring. Before moving forward, I do want to confirm your trailer setup since this controller is designed for one or two brake axles.

Are you running a tandem axle on your trailers?

expert reply by: Heather A

0

Larry O.

5/5/2026

I have a 1 year old 16ft goose neck and a brand new 18ft light flat bed trailer. Both have two axles and 4 brakes. Both trailers have the same issue. Trailer brakes work put are very weak. I did some more testing with a volt meters at the controller and one at the rear 7 pin. There is a 1 volt drop between the control and 7 pin. After more inspection of the factory trailer brake system on the truck I noticed that looks like the blue wire coming out from the controller ending at the rear 7 plug connector is a 14 gauge wire. This is to small. It should be a 10 gauge wire. I am thinking that the small 14 gauge wire along with any plugs along the way is not capable of handling the amps required. My next step is to run a 10 gauge jumper from the controller out put to the 7 pin and see if there is an improvement. Do you know the amperage required per trailer brake times 4=. Thanks Larry

Heather A.

5/5/2026

@LarryO For a typical tandem axle trailer with four electric brake assemblies, you should expect around 15 to 16.3 amps total draw at full 12V output, which comes out to roughly 3.5–4 amps per brake depending on the size and rating. That range is normal for most 12" brake setups commonly found on gooseneck trailers. Running a 10-gauge jumper is a fair test, but it likely won’t fix the problem if the controller itself is only producing 4–5 volts. When you tested the 7-way plug, was the trailer plugged in? Sometimes the 12 volt is not active without the trailer plugged in.

Larry

5/5/2026

Yes. The trailer was plugged i and driven during testing. Thanks

Larry

5/12/2026

Update. First off let me say after having my new 2025 f250 into the dealer a least 7 time for week trailer brakes and finely a new updated trailer brake controller and programing I still had very week trailer brakes. It is a ford problem and I came to realize I have to fix it myself so I ordered the Redarc Tow-Pro Trail Brake Controller. While I was waiting for the Redarc Tow-Pro Trail Brake Controller w/ Custom Harness - Dash Knob - Off-Road Mode to arrive I did add a 10-gauge wire from the factory brake controller to the 7pin at the back of the truck. I no longer have a 1 volt drop put it did not solve the week trailer brakes. Today the Redarc Tow-Pro Trail Brake Controller arrived. Problem solved. Works grate. Now I have complete control of the trailer brakes. I highly recommend any one with a 2023 to 2025 ford f250 / f350 to install this kit. It simply plugs into a pigtail near the factory trailer brake controller.

See All (4) Replies to Larry O. ∨

Answer 1

Great questions Dennis, happy to help! Yes, the Redarc Tow-Pro Liberty Brake Controller #RED44UR is a proportional, inertia brake controller. Once installed and calibrated, it uses an internal accelerometer to automatically apply the trailer brakes…

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Answer 2

That's a very good question, we tend to be extra cautious and say to use 10 gauge wire because that would be more than enough. When you get into longer trailers that will end up using a lot of wire the heavier gauge wire becomes more necessary.…

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Answer 3

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Fixing Weak Trailer Brakes on 2025 Ford F250 with Redarc Tow-Pro Liberty Installation

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