Diagram Showing How Trailer Brakes are Wired

Question

Question:

when you wire tandem axles, do you do it in series or parallel ? how about a diagram ?

asked by: phil

0

Expert Reply:

The brake wire providing voltage is wired in parallel, with one lead from each magnet being grounded to the trailer frame.

We have a great Wiring Help Page that shows a diagram, I will provide a link to it below.

expert reply by: Mike L

0

Ed C.

6/30/2025

Just got electric brake setup to replace hydraulics. New backing plate with complete setup shoes, magnets etc. I also got the breakaway switch., new 7 pin cord, and wire for trailer. Now :…. How do I wire the whole thing up? Ed

Mike L.

7/2/2025

@EdC I highly recommend running your trailer's 7-way whip into a junction box like # 3375601100. This provides an organized and clean place to make all your connections so they're protected from the elements. I don't know which whip you have, but be aware that the color coding of the wires in the whip might be different than those of the trailer. Each brake assembly will ground to the trailer frame, with the other wire carrying voltage from the brake controller. Join those into a single lead running to the trailer tongue where you'll install the junction box. The brake output circuit from the vehicle (usually a blue wire) will install on the same junction box terminal as the wire you ran forward from the brakes. I'll link you to a help article that explains this, there are some really nice, easy to understand wiring diagrams that I hope you'll find helpful. I'll also link to an install video for the junction box.

Helpful Links

faq-wiring.aspx

tv-review-buyers-trailer-junction-box-3375601100.aspx

Ed

7/2/2025

@MikeL thank you.

Ed C.

7/2/2025

@Ed thanks Mike can you talk to ma about the breakaway box wiring up? How’s that work?

See All (7) Replies to Ed C. ∨

Answer 1

Hello Jeffrey, Thanks for writing in. Just as long as your current hubs are in good condition, you will be able to use them with electric brakes as well, as long as they are standard 7" brake drums with the correct 4-bolt mounting flange (which…

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Answer 2

It sounds like you are speaking of the wires for the brake magnets. If this is correct, you will need to connect one of the wires to the brake controller output wire on your trailer connector and the other wire will need to be grounded to a clean…

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Answer 3

Hey Steve, you are on the right track but instead of the #RD58SR you'd want the part #118266 instead as this kit completes a 7-way in your 2008 Nissan Frontier while using the factory wiring for a much easier install without any splicing. Then…

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Answer 4

Even on manufactured trailers wiring colors can vary so there is no way to say for sure. The only way to know which wire is tied to which function is to trace the wire back. On an SAE standard 7-way the brown wire would be the tail/running lights. On…

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Answer 5

You should be getting 12 volts on the running light circuit when the running lights are turned on. If not, the problem is either in the connector or upstream from there. The first thing you should check is the trailer connector on your towing…

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Answer 6

The Dexter hub you referenced, 8-201, is a 5,200 lb hub, though a 5 on 4-1/2 bolt pattern does not come on 5,200 lb hubs. The correct bearings for the 5,200 lb hub are #25580 and #LM67048, while the proper races are #25520 and #LM67010. I have…

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Answer 7

Hey, Andre. We have just the hub/drum for you! Since you have a 3.5k axle you will want the trailer hub and drum assembly part #TRU58AV.It come pre-greased so will make for a pretty easy install. This drum does use a typical bearing combination…

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Answer 8

I recommend using the Tandem-Axle Trailer Hangers #H248 for your boat trailer. The center hanger is slightly taller by 3/8" which will work well as the Road Armor Shock Absorbing Equalizer Kit #LC696740 pivots on the hanger. The Lippert AP Kit…

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Answer 9

The outer diameter of the bushing that comes with the 4-Leaf Double-Eye Spring #e54SR is 11/16 of an inch. For a replacement bushing for the #e54SR you would want a Nylon Bushing #TRBU11566. I attached a link to all the bushings we offer also.

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Answer 10

We actually have a variety of brake components here at etrailer.com that I have linked for you to filter through. Usually what we see is that it's more cost-effective to replace the entire brake assembly instead of piecing it out plus you know…

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Answer 11

There are Retrax XRs for your 2020 Ford F-250 Super Duty which have rails that will allow you to install a rack system to carry four of the Yakima FrontLoader Wheel Mount Bike Carrier #Y02103. The correct Retrax XR tonneau cover will depend on the…

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Answer 12

DOT5 brake fluid is what you'd want to use in the Dexter surge actuator part #DX89FR. If the breakaway pin was pulled it would be replaceable. The breakaway cable is replaceable.

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Diagram Showing How Trailer Brakes are Wired

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