Trailer Wiring Basics and Tips

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Trailer wiring is by far the most defamed aspect as far as trailer mechanics are concerned. Considering the numerous pitfalls of wiring repairs, and the stressful tracing down of broken wires, bad connections, and intermittent problems. And once the problem gets discovered, you sure do not want to escalate it by using the wrong cable. It is worth noting that not all wires are created equal. Quite the contrary, trailer wire types and gauges are quite specific.

Basics and Tips on Wiring a Trailer

The first crucial rule is, it is imperative never to use a reliable trailer. Solid wires are well suited for houses and industrial use. So unless you are using it for bailing cable, it should never be used in your trailer. It is highly recommended you use flexible trailer wiring.

Stranded wires are an excellent example of flexibility. Solid core, on the other hand, though it can bend, cannot do so repeatedly. Using solid core wire in any trailing application is highly frowned over. So before you get to how to wire a trailer, you need first to understand the type of connectors you need and get the right wires.

Here is some crucial information you need to know next time you are thinking of wiring your trailer.

How To Choose The Right Trailer Wire

Choosing the proper wire is crucial when it comes to wiring your trailer to your RV or truck, especially when adding electronic or electrical components such as racing electronics or high-end audio to it. There are several factors you need to consider; size, material, and color. 

Size Of Wires

Sizing is the core issue for wiring. Since the wire is the conduit of electrical current, its length, gauge, and thickness directly determine how much current it can carry. Signal wires, like those from a sensor to a computer, need not be massive as they require minimal current (amperage). 

The primary power wire applications, on the other hand, like electric motors, alternators, and other high-draw items, require bigger wires to support the load. The distance from the source is directly proportional to the diameter of the cable. 

Also, an issue of voltage drop may arise. Any time you run a wire, it leads to a certain amount of voltage drop. Like a water hose, the longer it leads to a corresponding decrease in pressure of the outlet. In electrical circuits, the voltage drop is fixable using larger gauge wires.  

In some instances, such as not having the correct size, the large wires that can support large amounts of current may get you into trouble. You should, however, go for the significant options and not the smaller ones. That is mainly because most of the standard smaller wires are mostly used for signals such as sensors. 

Material Of Wire

The material used to make the wire is just as vital as the gauge. For any electrical application, copper is the most recommended. However, it is expensive, and other alternatives such as aluminum and copper-clad aluminum may come in handy. The two main types are CCA (Copper Clad Aluminum) and OFC (Oxygen Free Copper). Aluminum is known to conduct about 40% less electricity as compared to copper. That translates to comprehensive wiring for more heat. 

Also, aluminum is poorly characterized by corroding. This natural corrosion is hastened in the presence of electricity. And when combined with the moisture in the air, the electrolysis process takes place, which in turn adversely affects the conducting ability of the wire. You may have come across the byproduct of electrolysis if you found a whitish powder covering when you open up a cable. Even though this may also happen to copper, it takes a longer wire and results in the cable’s green tinting. 

That should be put into much consideration, especially with signal wires. These wires being 18 gauge or even smaller, the quality is even more essential as any additional resistance translates to degrading of the signal, and your trailer will suffer. Before you purchase any wire, you need to ask beforehand as there are many available cheap wiring kits and spools that use CCA instead of OFC. You are advised to stick to OFC. 

Trailer Wiring Color Code

At first, this may seem not to be an essential factor. But its importance comes in when trying to trace a faulty circuit. To take the hassle out of racking your brain, you need to color-code your wires with an accessory. That’ll give you a comfortable time during installation and troubleshooting. 

Types of Trailer Wiring Connector Right for You

A trailer wiring connector, in simpler terms, is that which is used to link the electrical system of your car to that of the trailer. That comes in handy when your trailer has blocked your car’s rear to enable other drivers to see your car’s lights. That not only serves to ensure safety but is also required by the law. These regulations may vary depending on the state, so you need to verify your region’s requirements to be in compliance. Below is a list of some of the standard wiring connectors and their functioning. 

Types of Sockets and Plugs

Just like how you plug your appliances into sockets on the walls in the house, cars similarly require you to connect the trailer in mention, into an outlet on the vehicle. Sockets and plugs come in varying shapes, commonly round, RV blade, and flat. 


These have the pins linearly in one single row. In general, the flat connectors are associated with a lower pin number and are mostly used to tow smaller loads that do not require many functions. 

RV blade and round

These are both rounds with their pins assuming a circular arrangement. For connectors with six pins and higher, there is one taking the middle position. At times they may come with a lower number of pins, but they are reliable for use with larger loads requiring more functions as they commonly have a higher pin count.

For RV blade and round connectors, the shapes of the plug and outlet are similar, but as for the holes and pins, the forms vary. Round caps are characterized by round holes and pins, RV plugs, on the other hand, have rectangular holes and bolts. 

Pin Number

Back at home, household outlets mostly work with either three-pronged or two-pronged plugs. But with trailers, substitute prongs with pins such that as a household plug has four prongs, your trailer will require a four-pin wiring connector. Trailer connectors commonly range from five to seven pins. The number of pins in a connector is directly proportional to the total functions that can be handled by it. 

Five-pin and four-pin 

One of the pins in a connector is ground, meaning the four-pin connector can control three things, and the five-pin connector, four. The four-pin connector deals with lights, from the brake lights, turn signals, to the taillights. When you add the five-pin connector, you have electric brakes or reverse lights. 

Six-pin Connector

With the six-pin connector, you are adding a 12-volt connection. This addition is more of convenience rather than safety. Instead of controlling lights, the sixth pin, known as hot lead, allows you to charge your trailer’s battery. That is necessary if you need to haul a small-sized camper trailer, but unnecessary when towing a boat or such item.  

Seven-pin Connector

This connector enhances the capacities. It incorporates some capabilities of smaller pin connectors so that you have all-in-one functions; electric brakes, lighting functions, and the 12-volt connection. Once again, this only comes in handy when towing an RV or a camper.

Final Verdict

And that’s everything you need before wiring your trailer. Wiring a trailer can be a tough task, but with the right guide on how to wire a trailer, you should be able to handle it pretty well. The wide range of trailer wiring connectors makes sure you have the correct features regardless of the type of load you need to haul; choose one to tow your trailer legally and safely.