Why am I Only Getting 6 Volts of Power Back at My New Dexter Brakes, but the Full 12 Volts at 7Way?  

Question:

Expert Reply:

Hello Greg,

I am sorry to hear you are having issues after installing your new Dexter Electric Trailer Brakes - 10" - Left/Right Hand Assemblies - 3.5K # 23-26-27.

First off, nice work taking on the whole brake replacement instead of just fixing the one that quit. That’s the smart way to avoid repeat headaches down the road. The big clue in your story is the voltage drop: you’ve got a healthy 12 volts at the truck’s socket, but only about 6 volts by the time it reaches the trailer’s brake wiring. That cut in half explains exactly why the brakes feel weak.

Electric brake magnets really need close to full battery voltage to clamp down properly. At 6 volts, they’ll kind of grab, but never strongly, which matches what you’re seeing with the wheels still being able to turn by hand and the trailer not helping much when you stop.

The usual suspects for this kind of drop are the wiring and the grounds. Many trailers are wired with fairly skinny wire (14–16 gauge), and with four magnets pulling 3–4 amps each, that wire just can’t carry the load without serious voltage loss. Grounds are just as important, if the brakes are only grounded through the trailer frame, corrosion or poor connections can add resistance that robs even more voltage. Running a proper 10-gauge power feed and a dedicated ground return from each brake back to your junction box is often the cure.

The best way to confirm what’s going on is with a direct test. Disconnect one brake and run a pair of 10-gauge jumper wires straight from a 12-volt battery to its two leads. If it grabs firmly, to the point where pliers stick hard to the magnet, then the brakes themselves are fine and your issue is just wiring and grounding. You can also use a clamp meter on the brake feed: with all four brakes engaged you should see around 12–16 amps total. If it’s much less, that tells you the magnets are starving.

One extra tip: whenever you’re testing brake function without driving, make sure to use the manual override on your brake controller rather than just pressing the brake pedal. The override sends full power straight to the trailer brakes, so you’re testing them directly without any of the truck’s braking mixed in. It’s the safest and clearest way to check how strong they really are. You would think that putting the controller to high and press the brakes would do the trick, but it does not.

I also attached a help article for trailer brakes, please read the "Step 4: "Break-in" New Brakes" so that you can make sure you are breaking them in the right way. This process is necessary.

We are a few days behind on answering questions, my apologies for that, were you able to get it figured out already? If so, what was the issue?

expert reply by: Kate F

0

Kate F.

9/29/2025

Hey Greg, Did you manage to resolve the issue with the voltage drop affecting your Dexter brakes? I'd love to hear what solution worked for you, as it could help others facing similar challenges.

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