Should Blue Wire From Brake Controller Have Constant Power

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Question:

I am hoping you can help. Should the blue wire from the back of the controller have constant power?

asked by: Daniel

0

Expert Reply:

The blue wire coming from the back of your Tekonsha Voyager Brake Controller # 39510 is for brake output to the 7-Way connector. This wire should only have power with the brake pedal depressed or the manual override activated on the brake controller. If you are getting constant power on this blue wire this may be an indication that the controller is bad but there is an easy way to test this.

You will want to first sever the blue wire several inches from the back of the controller. Then use a circuit tester like # PTW2993 to test the end of the blue wire coming out of the controller. This should only have power when you apply the manual override. If you are still getting power there at idle, then there is an internal issue on the controller and it will need to be replaced.

If a replacement is in order, I highly recommend the Tekonsha Prodigy P2 # 90885. This is a great proportional controller that features continuous diagnostics to alert you to any potential issues and comes with a limited lifetime warranty.

If it tests normal (only showing power with the manual override) then go ahead and reconnect the blue wire. You will then want to move back to the 7-Way connector on your vehicle. Inspect the connector for any dirt or corrosion that might be built-up around and behind the pins. This can cause a short that might be bleeding over into the brake output pin. Clean the connector out as needed.

Then test the brake output pin on the 7-Way (5 o'clock position) to make sure it is only getting power with the manual override on the brake controller activated. If it shows power at any other time, then the issue is somewhere between the brake controller and the 7-Way. If this is the case, you will just need to inspect the wiring along the vehicle for any damaged or exposed sections, fixing/replacing as needed.

expert reply by: Chris R

0

Nick M.

7/15/2020

The test you describe above... is it implied that the trailer is plugged into the back of the tow vehicle? Is it true that the blue wire would test differently with the trailer plugged in or not? Thanks,

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Chris R.

7/20/2020

If you slide the manual override on the brake controller, it should send back full power on that blue brake output wire regardless of whether or not a trailer is attached. So you can perform this test without hooking up the trailer.

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Dave D.

4/6/2025

@ChrisR What about power on the trailer side? I have 12v on the blue pin at the connector(trailer side)

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Timothy

4/6/2025

@ChrisR I am having a similar issue trying to figure out what post go where on my new seven pin junction box it seems they mislabeled some of them. The Blue post that they say I should put the brake controller wire on is 12 V hot when the engine is running I don’t think this is correct. There is another post that doesn’t have power. I wonder if that should go there.

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Kate F.

4/7/2025

@Timothy Hey Timothy, You're right to question the labeling on that junction box. The blue wire is supposed to be for the brake controller output, which means it should only have power when you're pressing the brake pedal or using the manual override on your controller. It definitely shouldn’t be hot just because the engine is running. If that post is constantly live, then it’s most likely mislabeled. On a standard 7-way RV plug, the blue wire is for the trailer brakes, the black wire is your 12V power (used for charging a trailer battery or running 12V accessories), and the white wire is ground. There are also wires for turn signals, tail lights, and reverse, but for this situation, focus on those main three. You can use a multimeter to check which post is which, or something like the # PTW2993. The black (12V) should be hot with the ignition on, and the blue (brake controller) should only show voltage when you hit the brakes or use the manual slider. It’s not uncommon for junction boxes to be labeled incorrectly, so the best bet is to go by function, not the printed labels. Once you figure out what each wire does, you can relabel the box to avoid confusion later. Let me know how things work out.

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See All (5) Replies to Nick M. ∨

Answer 1

It is normal to have continuity between the brake(blue) wire and ground(white) wire. The electric trailer brake is an electromagnet when it has power it attracts to the steel inside the hub/drum. If you are having issues with your trailer brakes…

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Answer 2

No you should not have constant power on the brake output pin, the blue wire should only have power with the brake pedal depressed in the vehicle or the brake controller manual override is activated. If the blue wire has a constant 12V then it is an…

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Answer 3

The battery you use for a break away system needs to be able to power the trailer brakes on full for 15 minutes. A 12 volt battery rated for 5 amp hours is normally used, unless you have 3 axles each with brakes, then you would benefit more from a 9…

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Answer 4

I went ahead and hunted down a wiring diagram for the WH6GA water heater, and was able to find a diagram (attached below). This tank has a 10K Btu heating capacity, a 6 gal tank, measures 12-3/4"H x 12-3/4"W x 19-7/8"D, and is a direct…

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Answer 5

The Model 32 part number 903211000 you mentioned references a Kwikee 32 series powered double step just like the part #LC3722616 that you referenced so this is what you'd need.

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Answer 6

For a wire loom for 7-way wiring we recommend 1/2 inch diameter like part #459075-1 that is sold by the foot. I have a 7-way adapter on my desk that has a wire loom on it that is 1/2 inch so I know this size would be correct.

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Answer 7

You will need to use a different wire for the stop light circuit for installing your brake controller. You need to find a circuit that has 12 volts only when the brakes are applied. The easiest place to find this circuit is at the brake pedal switch…

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Answer 8

All the brake controller needs to sense a trailer connection so that you can test it is a slight amperage draw on the output circuit. For that you can use a circuit tester like the part #PTW2993 with one pin grounded and the other on the output pin.…

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Answer 9

This is definitely something that is frustrating and unfortunately, my answer is not going to be much better. When we have brought this to Dexter in the past, they have told us that their Electric Over Hydraulic actuators like the Dexter DX Series…

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Answer 10

I am sorry to hear you are having an issue with your Dexter DX Series Electric Over Hydraulic Brake Actuator for Drum Brakes - 1,000 psi #K71-650. When I reached out to Dexter and they had a few thoughts. First is to make sure that the drum brakes…

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Answer 11

If you are looking for a way to power the trailer brakes you would not run the blue wire of the 7-way to the positive post of your battery. Instead you would run that wire up to the blue wire of a brake controller like the part #90885 that you…

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Answer 12

Yes, you can replace a weld-on surge brake actuator with a bolt-on surge brake actuator and you can weld a bolt-on surge brake actuator to the trailer. If you are handy with a welder and have one available then I prefer this method over the other as…

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Should Blue Wire From Brake Controller Have Constant Power

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