The comprehensive guide to trailer wiring diagram

Welcome to DeyTrade, your trusted partner for reliable electrical accessories. You have decided to buy a trailer and are now faced with the question of correct wiring? Don’t worry! In our comprehensive guide to trailer wiring diagram, we explain everything you need to know to wire your trailers safely and efficiently. Whether you have a 7-pin or 13-pin connector, need help with troubleshooting or just want to learn more about the world of the trailer wiring diagram – you’ve come to the right place. Let’s discover the world of trailer wiring diagrams together!

The necessity of trailer pin assignment

A trailer needs to be properly powered for road use to ensure that tail lights, brake lights, turn signals and other important functions work properly. This is where the trailer connector comes into play, providing an important bridge between the trailer’s lighting and the towing vehicle’s on-board electronics. The assignment of the trailer connector provides information about which cable assumes which function in the connector.

So a trailer wiring diagram is a visual representation or guide showing how the wiring is laid out in a trailer. The purpose of the diagram is to help in connecting the vehicle to the trailer correctly, ensuring all the lights and signals work as they should. This is important not only for safety but also because many jurisdictions require trailers to have functional lighting systems for road use.

Difference between 7-pin and 13-pin connector pin assignment

There are two common types of connector pin assignments for trailers: the 7-pin and the 13-pin connector. While older trailers are usually still equipped with a 7-pin connector, modern trailers are predominantly equipped with the 13-pin connector. The 7-pin connector only allows the transmission of basic electrical functions, such as turn signals and brake lights. The 13-pin connector, on the other hand, offers a variety of other functions. In addition to the basic functions, this connection provides a charging line, a steady plus and a reversing light. Furthermore, this connection is splash-proof, which prevents damage to the electrical system.

Details on the connectors of your trailer

In this section we want to give you detailed information about an essential element of your trailer – the connectors. Often underestimated, they are the heart of any safe and smooth ride. They ensure that the electrical functions of your trailer, such as brakes, lights and signaling systems, always work properly. Connectors are usually available with different pin numbers and arrangements, the most common types being 7-pin and 13-pin. Each pin of these connectors is responsible for a specific function, for example, the brake light, the reversing light or the turn signals.

The 13-pin plug assignment according to ISO

The 13-pin plug layout is the standard version for modern trailers and offers a wide range of functions. It has 13 screw terminals and a black plastic housing. The pin assignment corresponds to the DIN/ISO standard and the cable colors are for information only.

The 7-pin plug assignment according to ISO

The 7-pin pin assignment is an older version and is often used with older trailers. It has 7 flat plug connections and a black plastic housing. Here, too, the pin assignment corresponds to the DIN/ISO standard.

trailer wiring diagram for 7- and 13-pin connectors

DeyTrade provides you with information about the pin assignment of the 7-pole plugs (no. 1-7) and the 13-pin plugs (no. 1-13). It is important to note that the wire colors for contacts 9-11 and 13 may vary. The 7-pin connector is mainly used for smaller trailers or bicycle carriers and contains the basic light functions such as rear lights, turn signals and brake lights. The 13-pin connector provides additional connections for convenience functions such as reversing lights, rear fog lights and continuous power, which is useful for larger trailers or caravans with additional electrical equipment.

Converting a trailer plug

If your towing vehicle is equipped with a 13-pin socket, but your trailer still has a 7-pin connection, you can make a trouble-free connection with the help of an adapter. However, it is advisable to remove the adapter after use to prevent water from getting into the socket via the adapter. It is also possible to replace the old trailer plug with a new 13-pin plug in the long term. Ensure to study the trailer wiring diagram first.

Maintenance and care of the trailer plug

Regular care and maintenance is essential for optimal functioning of the plug. In the event of a malfunction, never use water to clean the contacts. Instead, you can use contact spray to remove contamination. Regular inspections of the electrical wiring can help to detect and repair damage at an early stage.

Frequently asked questions (FAQs) about the trailer wiring diagram

Here you will find answers to some of the most frequently asked questions about the trailer wiring diagram:

Why is the trailer wiring diagram important?

The trailer wiring diagram is important because it ensures that your trailer’s lights and other functions are properly connected to your vehicle’s onboard electronics. It provides important information about which cable performs which function in the connector.

What is the difference between a 7-pin and a 13-pin plug assignment?

A 7-pin connector allows the transmission of basic electrical functions, such as turn signals and brake lights. A 13-pin plug, on the other hand, provides a variety of other functions, including a charging line, a steady plus and a reversing light. You can read about the functions in the corresponding trailer wiring diagram. It is also splash-proof, which protects the electrical system. 

Can I convert a 7-pin trailer plug to a 13-pin one?

Yes, you can replace the old trailer plug with a new 13-pin plug. Alternatively, you can use an adapter to connect a 7-pin trailer to a 13-pin socket. Make sure to be informed about the trailer wiring diagram of the used plug.

How do I care for my trailer connector?

To care for the plug, you should clean it regularly with contact spray to remove contamination from oil, grease deposits and condensation. It is also advisable to check the electrical wiring regularly to detect and repair damage at an early stage.

What happens if I connect the trailer connector incorrectly?

Incorrect connection assignment can cause damage to the electronics of the towing vehicle and impair the functions of the trailer. It is therefore important to connect the trailer connector correctly. The trailer wiring diagram of the respective connector helps here.

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