Have you ever been in a situation where you had to connect a trailer to your vehicle and found yourself dazed at the sight of colorful wires and figured not knowing where to begin? If you do not have the right wiring harness there is the danger of having the equipment functionality being mismatched or even increased chance of an accident. Whether it’s for hauling equipment or transporting cargo, standard trailer wiring color codes can make your job easier and more reliable. To address these issues we need to have some knowledge of the codes that govern the use of basic cable colors.
A trailer cable is a cable designed for the electrical connection between the trailer and the towing vehicle. It is abrasion-resistant, oil-resistant and highly flexible while adapting to the conditions of the trailer on the move. To match different needs there are usually several types:
Trailer Cable Type
4-Pin Flat Wiring
The 4-pin flat connector is one of the most widely used types for small trailers. It supports basic lighting functions including tail lights, brake lights and turn signals. It has a simple structure and is easy to install and maintain.
5-Pin Flat Wiring
The 5-pin flat connector adds a wire for auxiliary functions, such as reverse lights, to the functionality of the 4-pin connector. This type is typically used for trailers that require additional lighting features. If your trailer has an emergency brake system, this connector can also help to disengage the brakes when backing up.
6-Pin Circular Wiring
The 6-pin circular connector is typically used for medium-sized trailers, such as horse trailers or utility trailers with electric brakes. Its circular design provides a stronger connection than flat connectors.
7-Pin Circular Wiring
The 7-pin circular connector is the most versatile and is commonly used on large trailers, including RVs, campers, and heavy-duty trailers. It is also known as the RV type connector. This connector is critical for trailers with multiple axles or advanced electrical systems.
To assist you in identifying the wire types easily and connecting them correctly, the trailer wiring diagrams along with the trailer wire color codes have been made available and can serve as a important reference for the process of trailer wiring.
Trailer Wire Color Codes
Why do we need a color standard? The purpose of trailer cable color coding is to furnish every electrical wire with a unique identity. Having different colors of wires makes the installation processes easier, and the maintenance and trouble shooting is also logical and more efficient. Keep reading below as this guide will help you quickly figure out what each wire does.
Standard Color Codes for 4 Pin Trailer Wiring
- White: Ground wire
- Brown: Tail lights or running lights
- Yellow: Left turn signal and brake light
- Green: Right turn signal and brake light
Standard Color Codes for 5-Pin Trailer Wiring
- White: Ground wire
- Brown: Tail lights or running lights
- Yellow: Left turn signal and brake light
- Green: Right turn signal and brake light
- Blue: Electric brakes
Standard Color Codes for 6-Pin Trailer Wiring
- White: Ground wire
- Brown: Tail lights or running lights
- Yellow: Left turn signal and brake light
- Green: Right turn signal and brake light
- Blue: Electric brakes
- Red or Black: Auxiliary power
Standard Color Codes for 7-Pin Trailer Wiring
SAE Standard
- White: Ground wire
- Brown: Tail lights or running lights
- Yellow: Left turn signal and brake light
- Green: Right turn signal and brake light
- Blue: Electric brakes
- Red or Black: Auxiliary power
- Purple: Backup Lights
RV Standard
- Green: Tail lights or running lights
- Yellow: Reverse Lights
- Brown: Right turn signal and brake light
- White: Ground wire
- Blue: Electric brakes
- Black: Battery hot lead
- Red: Left turn signal and brake light
SAE Standard vs RV Standard
Standard color coding for 7-pin trailer cables falls into two main categories: SAE Standard (Society of Automotive Engineers Standard) and RV Standard (RV Standard, often referred to as the standard set by the RVIA (RV Industry Association) and NFPA (National Fire Protection Association)). Both standards are identical in terms of connection function and pin location and differ only in color coding.
Simply put, the 7-pin plugs and sockets are physically compatible, meaning that both standards will apply to the same trailer. A trailer that follows the SAE standard can be connected to a vehicle that follows the RV standard and vice versa. But when we come across situations where differences arise due to regional customs or manufacturer-specific designs. Here’s an important principle: Always let the function guide you.
Trailer Wiring Made Easy: Pro Tips
Wiring the Ground Wire
First and foremost, connect the ground wire to the trailer frame as a first priority. Self-tapping screws or bolts may be used to make this connection. Care should be taken to ensure that the earthing points are free of paint or rust. A good ground connection is essential to secure that your trailer lights work properly; poor grounding can lead to intermittent light failure.
Wiring the Tail Lights
Next, brown wire must be connected to the taillights according to the color code for trailer lights. The wire provides power to the running lights, which light up in sync when the vehicle’s headlights are on. When wiring, align the wires neatly along the trailer frame and secure them with tie wraps or cable clips to avoid sagging or damage to the wires.
Wiring the brake lights and the turn signal flasher
Then, connect the yellow wires to the brake lights and turn signals on the left side. Similarly, connect the green wires to the brake lights and turn signals on the right side. These wires ensure that the trailer’s brake lights and turn signals are synchronized with the tow vehicle. In case the trailer has an electric brake system, the blue wire must be connected to the system so that the braking function of the trailer can be controlled from the tow vehicle.
How do I know which connector type my trailer needs?
Trailer Wire Size
Three common trailer cable gauges include 12 gauge, 14 gauge and 16 gauge. For longer trailers or applications that require carrying higher currents, such as braking systems, 14 gauge or thicker 12 gauge wire is recommended to minimize voltage drop and ensure adequate current supply. The 16 gauge cables specialize in low-power signal transmission, such as led lighting.
The connector type depends on the electrical requirements of the trailer. For basic lighting, a 4-pin flat connector works well. If your trailer has power brakes or other features, a 6- or 7-way trailer wire may be required. Also, verify that your towing vehicle supports the type of connector required; some vehicles may require adapters or converters to match different types of trailer connectors.
Need further help?
If the trailer was purchased new, consult the owner’s manual or consult a specialty manufacturer. For example ZW CABLE will recommend the type of connector best suited for that trailer as well as provide the best quality trailer cable products.
Based on the information above, We believe you are now able to identify the variety of trailer cable color meaning and how to select the appropriate one. But at the same time, it is rather possible that you have sprung up quite a few questions, what to do for instance, when the trailer lights do not light up? Or what to do if there is no standard color cable? Do not worry, we have worked out the most of frequent questions which are supposed to help you resolve these confusions.
FAQs
What should I do if my trailer lights aren’t working?
Start by inspecting the wiring for damage, such as frayed or broken wires. Check the connectors for corrosion or loose connections. Use a multimeter to test the electrical flow. Replace damaged wires or clean corroded connectors to restore functionality.
How can I test my trailer wiring?
To troubleshoot the trailer wiring, the best way is to check each wire’s functionality using a multimeter or test light. An easy way is to test the ground wire first and verify that the circuit is intact. After that, assess the operational status of the tail lights, brake lights, turn signals and more. Test all components before departure to secure they are functioning properly.
Can I use different wire colors if I don’t have the standard ones?
Yes, but you must label the wires clearly to avoid confusion. The function of the wire matters more than its color. Use a wiring diagram to match the wires correctly, regardless of their color.
How do I protect my trailer wiring from weather damage?
Use heat shrink tubing, electrical tape, or conduit to cover exposed wires. Secure the wiring with zip ties or cable clamps to prevent sagging or rubbing against sharp edges. Regularly inspect the wiring for wear and tear caused by weather or road debris. Store your trailer indoors or use a weatherproof cover when not in use. The practice shields your wiring from rain, snow, and UV damage.
