Trailers come in all shapes and sizes, and so do their electric systems. Whether you’re hauling a small utility trailer or a large fifth wheel, you need to make sure your trailer lights are in compliance with the law and functioning properly.
To do that, you need to understand the standard trailer wiring diagram. In this article, we’ll explain the ins and outs of trailer wiring, including how to troubleshoot common problems and how to wire your trailer for best results.
What is a Trailer Wiring Diagram?
A trailer wiring diagram is a schematic representation of the electrical system of a trailer. It shows how the electrical components are connected and allows you to troubleshoot any issues that may arise.
There are several types of wiring diagrams for trailers, but the most common is the 7-way RV plug. This plug is used for trailers that have electric brakes, and it provides power to all the necessary components, including turn signals, brake lights, and taillights.
The 7-Way RV Plug
The 7-way RV plug has seven pins, each of which serves a different function. The pins are arranged in a specific order, and are labelled as follows:
| Pin Number | Function |
|---|---|
| 1 | Ground |
| 2 | Left Turn/Brake Light |
| 3 | Right Turn/Brake Light |
| 4 | Taillight |
| 5 | Reverse Light |
| 6 | Electric Brake |
| 7 | 12V Battery |
Each pin is colour-coded for easy identification. Ground is white, left turn/brake is yellow, right turn/brake is green, taillight is brown, reverse light is black or grey, electric brake is blue, and 12V battery is red.
How to Wire a Trailer
Wiring a trailer is not difficult, but it does require some basic knowledge of electrical systems. The first step is to choose the right wiring harness for your trailer.
There are several types of wiring harnesses available, including 4-way, 5-way, 6-way, and 7-way. The most common is the 7-way RV plug, which provides the most comprehensive electrical system for your trailer.
Step-by-Step Guide to Wiring a Trailer
Follow these steps to wire your trailer correctly:
- Choose the right wiring harness for your trailer.
- Mount the harness onto the trailer tongue.
- Run the wires through the trailer frame and secure them with zip ties.
- Connect the wires to the appropriate electrical components on the trailer.
- Connect the harness to your vehicle’s electrical system.
- Test the trailer lights to ensure they are functioning properly.
Common Trailer Wiring Problems and How to Fix Them
Just like any other electrical system, trailers can experience issues with their wiring. Here are some common problems and how to troubleshoot them:
No Power to the Trailer Lights
If your trailer lights are not receiving power, the first step is to check the connection between the trailer and the vehicle. Make sure the harness is properly connected and that all the wires are in good condition. If that doesn’t work, check the fuses and relays in your vehicle’s electrical system.
Blown Fuses
If one of your trailer lights is not working, it may be due to a blown fuse. Check the fuses in your vehicle’s electrical system and replace any that are blown.
Corroded Wires
Over time, the wires in your trailer’s electrical system can become corroded, which can interfere with the flow of electricity. If you see any signs of corrosion, replace the affected wires.
FAQs About Standard Trailer Wiring Diagrams
1. How do I choose the right wiring harness for my trailer?
The right wiring harness for your trailer depends on the type of trailer you have and what electrical components it has. The most comprehensive wiring harness is the 7-way RV plug, which is suitable for trailers with electric brakes.
2. Can I wire my trailer without a wiring harness?
No, it is not recommended to wire your trailer without a wiring harness. A wiring harness provides a safe and reliable connection between your trailer and your vehicle’s electrical system.
3. Do I need to use a specific type of wire for my trailer?
Yes, you should use wire that is specifically designed for use in a trailer’s electrical system. This wire is heavier and more durable than standard electrical wire and is designed to withstand the harsh conditions of the road.
4. Can I replace a blown fuse with a higher amperage fuse?
No, you should always replace a blown fuse with a fuse of the same amperage. Using a higher amperage fuse can cause damage to your trailer’s electrical system and create a safety hazard.
5. What should I do if my trailer lights are not working?
If your trailer lights are not working, start by checking the wiring harness and the connections. If that doesn’t work, check the fuses and relays in your vehicle’s electrical system. If you still can’t find the problem, consult a professional mechanic or electrician.
Conclusion
Understanding how to wire your trailer and troubleshoot common problems is essential for ensuring that your trailer lights are functioning properly and that you’re in compliance with the law. By following the information in this article, you should be able to wire your trailer correctly and keep it in good working order.
