How To Wire A Trailer With Electric Brakes

If your trailer needs brakes and they're not already wired then you're probably wondering how to go about doing it yourself. Luckily, it's a fairly straightforward process and shouldn't take you too long to do.

In this guide, we've laid out the steps of how to wire your trailer with electric brakes as well as some other useful tips.

Do I Need Trailer Brakes?

If you have a light trailer then you may not be legally required to have independent trailer brakes installed as the brakes on your tow vehicle should be sufficient to safely bring you to a stop.

However, in most states, there are laws in place that require you to have brakes for your trailer if it weighs over 3,000 pounds when fully loaded.

The laws do vary between states so it's important that you check the specific requirements of any state that you intend to travel through before setting off.

For example, in California, you must have brakes on your trailer if it weighs over 1,500 pounds when loaded but in Alaska, the legal limit is 5,000 pounds.

Generally, it's best to install brakes for your trailer regardless of which states you are traveling through as they greatly increase your safety when towing.

We'd also recommend installing a brake controller to enhance your towing experience. Brake controllers can be fairly easy to install and are usually pretty affordable.

8 Steps For Wiring Your Electric Brakes

For all trailers, there is a requirement for a minimum of 4 functions when it comes to wiring. These are brake lights, tail lights, left turn signal, and right turn signal.

For light-duty trailers such as small campers, off-road trailers, light boat trailers, and small utility trailers 4 wires are connected to a 4-pin connector to enable these basic functions.

For this type of wiring, the white wire is the ground wire, the brown wire is connected to the tail lights, running lights, and side marker lights, the yellow wire is connected to the left brake light and left turn signal, and the green wire is connected to the right brake light and the right turn signal.

For trailers that require brakes, a connector with at least 5 pins will be needed. This is to accommodate a 5th blue wire that provides power for operating or disabling the brakes on the trailer.

Below, we give a simple explanation for wiring your electric brakes that is fairly universal and can be used in most situations. However, in some cases, there will be specific industrial standards you will need to follow.

Step 1

Firstly, you'll need to install the 6-conductor cable into your trailer frame. You'll then need to split the cable so that the blue, yellow, and brown wires can go down the left-hand side of the trailer and the green wire can go down the right-hand side.

You can ignore the black wire as this is not going to be used.

Step 2

Now, take the green wire and connect it to the right turn signal.

Step 3

Take the yellow wire and connect it to the left turn signal.

Step 4

Take the blue wire and connect it to the electric brakes.

Step 5

Now, you'll need to take the brown wire and connect it to the tail lights on both the right and left sides of the trailer, as well as the side marker lights. If your trailer is more than 80 inches wide then it will require a triple light bar at the rear center.

If this is the case, you'll need to connect the brown wire to this as well.

Step 6

Using a self-tapping screw, you'll need to attach the white wire to the trailer frame.

Step 7

Now, go back to the 5-pin connector and splice all of these wires you've just connected to the same color wire on the connector.

Step 8

Once this is all done, you simply need to tape all of the connections so that they're fully secure.

Wiring Trailer Brakes With a 7-Pin Connector

Some trailers have a 7-pin connector that has 2 extra connections for functions such as auxiliary power and backup lights. Wiring electric brakes for a trailer with a 7-pin connector is the same process as for a 5-pin connector.

The first 5 wires need to be connected in the same way that we have outlined above. Then, you can either ignore the other two connections or wire them up for other functions such as auxiliary power.

Trailer Wiring For Breakaway Kits

As well as having brakes fitted, it is also a legal requirement for many trailers to have a breakaway kit installed. In the majority of states, this is needed if the weight of your trailer is over 3,000 pounds when fully loaded but again, this does vary between states.

Breakaway kits automatically apply the brakes on the trailer if it becomes detached from the tow vehicle, so we'd always recommend using one whenever you're towing a trailer.

Different breakaway kit systems will sometimes have different wiring color schemes so always check the instructions from the manufacturer before you install one.

Generally, the wiring schematic for a breakaway kit is as follows. The battery is charged by the red wire (occasionally the black wire), the blue wire is used to power the brakes, and the white wire is used as the ground wire.

As mentioned, be sure to check the instructions for your specific system in case the schematics are different.

Trailer Wiring Routing

So, we've now established how to connect the wires to the relevant components and you may be wondering how to actually route them.

The best and safest way to route the wires is to nestle them around and into the trailer frame. Once they're nestled in, it's also recommendable to cover them with either a plastic conduit or a flexible conduit to give them a good layer of protection from the elements and from snagging.

The covering you use doesn't have to be fully watertight but we would highly recommend that you use some form of weather protection when you splice into the wires.

Tips On The Different Types Of Trailer Wiring

Trailer wiring sizes

There are lots of different wire sizes available for you to choose from and you'll notice that they're usually listed by 'gauge'. The smaller the number, the thicker the wire will be.

Typically, you would use a 16 gauge wire or higher for lighting and a thicker wire, such as a 12 or 14 gauge, for brakes.

Blue wire

The blue wire is the wire that's used to power the electric brakes on your trailer. It connects to the 5th pin of the connector but this is not always listed as standard.

Sometimes the 5th pin will be labeled as 'reverse lights' and sometimes the 5th pin will be used for disabling the brakes when reversing. This means that when using a 5-pin connector you'll need to make sure that you always check that the wires in your car match the functions of your trailer.

In the tow vehicle, the blue wire for electric brakes will go to the brake controller.

White wire

The white wire is very important as it is the negative or ground wire that connects to the vehicle battery's minus side. It serves this function for all of the trailer's lights and brakes, as well as any additional functions like auxiliary power and backup lights.

It is common for trailer owners to simply connect it to the trailer frame and then connect all of the other wires to the frame as well. Most of the time this will work but the ground section of the circuit is always the most likely to fail and cause electrical problems for your trailer.

The best way to avoid electrical issues is to run the ground wire along with all the other wires and then connect the ground from each individual wire directly to the white.

FAQS

Do I need a breakaway kit?

In most states in the US, you need a breakaway kit if your trailer weighs over 3,000 pounds when it's fully loaded. This differs from state to state so you need to make sure that you check the laws of any states you plan to tow in before beginning your journey.

As a rule, it's best to install a breakaway kit on any trailer where possible to keep you and other drivers as safe as possible.

If I have electric brakes do I need to have a brake controller?

Trailers that have electric brakes cannot be towed unless you have a brake controller installed. A brake controller allows you to control the brakes on your trailer from inside the cab of your towing vehicle. Without a controller, the brakes on your trailer simply won't work.

What are the risks of towing a heavy trailer without trailer brakes?

If you have a heavy trailer that should have brakes installed but doesn't you are putting yourself and other drivers at great risk. The added weight of a trailer significantly reduces your stopping distances and if your trailer doesn't have brakes then you run a real risk of jack-knifing.

Having brakes and a brake controller also means that you can control trailer sway when out on the road which is very important. If you're towing a heavy trailer without brakes and it begins to sway it will be incredibly difficult for you to bring it back under control safely.

How do I know if my trailer already has electric brakes?

Generally, you can tell if your trailer already has electric brakes if it has brakes installed but doesn't have an actuator.

The only time this would not be the case is if the trailer has hydraulic brakes but a previous owner has switched the actuator for a normal coupler and decided not to use the brakes.

Final Thoughts

Correctly wiring the electric brakes for your trailer is important to keep you safe when you're out on the roads. As you can see, it's not overly complicated and the advice in this guide should have you doing it yourself in no time.

Sources

https://itstillruns.com/wire-boss-snowplow-12064405.html

https://mechanicalelements.com/trailer-wiring-diagram/

https://www.elecbrakes.com/blog/can-standard-trailer-wiring-power-electric-brakes/

https://www.rvandplaya.com/how-much-can-you-tow-without-trailer-brakes/

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