Troubleshooting No Power for Brake Controller on 2025 Ford Ranger

Question

Question:

I have a 2025 Ford Ranger. It came with the 4-pin, but I bought the new wiring harness for the back and installed the 7-pin, no problem. I also have the factory brake controller port grey near the pedals. I bought the appropriate adapter to go from that port to the Redarc Liberty. Everything is installed correctly, but I dont seem to be getting power out of the factory port. I used a multimeter and tested, with a trailer connected and the truck recognizing it.

asked by: Allen

0

Expert Reply:

Hey Allen!

Thanks for reaching out! It sounds like you've already done quite a bit of troubleshooting, and I appreciate you checking the wiring with a multimeter. That helps narrow things down.

One thing that stands out is that your 2025 Ford Ranger originally came with a 4-pin connector rather than a factory 7-way. Even though you've upgraded the rear wiring and found the factory brake controller port under the dash, that doesn't necessarily mean all the circuits needed for the Redarc Tow-Pro Liberty are powered and ready to use.

I'd start by disconnecting the Redarc adapter and testing the truck's factory brake controller port directly. You should have a 12V power supply, a ground, a brake light signal that activates when you press the brake pedal, and a wire that carries the controller's output to the 7-way. Keep in mind that the brake output wire won't have power until the controller sends it, so it's normal for that circuit to show no voltage with the controller disconnected.

If you're not getting 12V on the power supply circuit, I'd check the trailer brake controller fuse using your owner's manual to identify the correct location. If the fuse is good, the next step would be having a Ford dealer check whether the brake controller circuit is fully equipped and enabled on your particular Ranger. I wouldn't recommend running additional power or modifying the factory wiring until that's confirmed.

I do have a couple of questions to help narrow this down. When you say you're not getting power from the factory port, are you referring specifically to the 12V power supply, or are you not seeing voltage on any of the terminals? Also, does the Redarc control knob light up at all when you connect your trailer?

expert reply by: Jerry B

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Allen

10/30/2026

I'm not seeming to get power out of the red/yellow power wire (the one that goes into the black power wire on the redarc adapter I believe. I tested from that wire with a good ground. The Blue knob does not light up at all unfortunately.

Jerry B.

10/30/2026

@Allen Thanks for checking that! You're correct that the red/yellow wire on your Ranger should supply 12V power to the black wire on the Redarc adapter. Since you're not getting any voltage there, that gives us a much better idea of where the problem is. The first thing I'd check is the trailer brake controller fuse in your Ranger's underhood fuse box. Your owner's manual will help identify the correct fuse. Since your truck originally came with a 4-way connector, it's possible that the brake controller power circuit wasn't fully equipped from the factory. I'd also recommend checking the red/yellow wire directly at the factory connector with the Redarc adapter unplugged. If you're still getting 0V using a known good ground, we've ruled out the adapter and controller as the cause of that missing power supply. If the fuse is good (and installed), but you still don't have power, I'd recommend checking with Ford to see whether your Ranger requires additional factory wiring or configuration to activate that circuit. I wouldn't recommend jumping power to that wire until we know exactly how Ford has it configured. One more question for you: when you upgraded from the 4-way to the 7-way, did you use a Ford factory wiring harness or an aftermarket conversion kit? That could help us determine whether there's another connection or component we're missing.

Allen

10/30/2026

@JerryB I actually used the correct harness from Ford to install the 7 pin and it works well.

Jerry B.

11/2/2026

@Allen Thanks for confirming that! That helps narrow things down quite a bit. Since your 7-way is working and you're not getting power from the red/yellow wire, I'm thinking the issue is on the truck's side rather than with the Redarc. I'd start by checking the 30 amp fuse #42 in the underhood fuse box. That's listed as the trailer brake module fuse for your Ranger. Since your truck originally came with a 4-way, there's a chance that fuse is missing or the circuit wasn't fully equipped from the factory. If the fuse checks out, we may need to get Ford involved to see if there's some additional wiring or programming needed.

John

11/1/2026

it was 100 percent perfect the installation instructions were very clear and accurate ,you cant go wrong with this product and E Trailer is the place to get it

Jerry B.

11/2/2026

@John We appreciate the kind words and feedback. Do you also have a 25 Ranger?

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Troubleshooting No Power for Brake Controller on 2025 Ford Ranger

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