7-pin trailer plug wiring diagram

This connector takes care of essential functions such as:

• Indicators
• Brake lights
• Rear lights
• Rear fog light

This type of connector is mainly used on simple or older trailers, including luggage trailers, cycle carriers and boat trailers. In situations where additional electrical functions are required, the 7-PIN connection is often no longer sufficient.

Wiring diagram for the 7-PIN connector

1. Left indicator | yellow
2. Rear fog light | blue/brown
3. Mass (for contacts 1 to 7) | white
4. Right-hand indicator | green
5. Rear light/side marker light and number plate right | brown
6. Brake lights | red
7. Rear light / side marker lights left | black

Although the ISO 1724 standard specifies blue for the rear fog light (PIN 2), in practice brown is also common.

Application in trailer lighting

This scheme is used for the connection between the vehicle and the trailer for standard trailer lighting. The connector acts as the link between the towing vehicle, the cabling and the lighting. A fault in the connection therefore has an immediate effect on the entire system. See the complete guide to trailer lighting for further explanation of how functions work, cabling and types of applications.

When a constant power supply or reversing lights are required, the 13-PIN connector in accordance with ISO 11446 is the right choice.

7-pin to 13-pin trailer plug adapters

If the towing vehicle and the trailer have different plug types, an adapter may be the solution. Examples of these include:

• Vehicle with a 13-PIN connection, trailer with a 7-PIN connector
• Vehicle with a 7-PIN connector, trailer with a 13-PIN connector

Please note: when using an adapter from 13 to 7, additional functions such as constant power and reversing lights remain inoperative. Only the basic lighting is supported.

CAN-bus interference with LED lighting

When a trailer fitted with LED lighting is connected via a 7-PIN connector, interference may occur. This is common in modern vehicles equipped with a CAN-bus system. Possible symptoms:

• Non-functioning or flashing lighting
• Fault messages on the dashboard
• Lighting which does not switch off after disconnection

These interferences are caused by the vehicle not recognising the low current consumption of LED lighting as the correct load.

Want to know more? Read the article:
Troubleshooting CAN-bus interference in LED lighting

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

A 7-PIN connector supports basic lighting only. A 13-PIN connector additionally enables functions such as reversing lights, constant current and caravan facilities. For modern vehicles and applications, 13-PIN is in many cases the better choice.

Connecting and troubleshooting interference

In our article on connecting trailer lighting, you’ll find useful tips on how to do it properly. With trailer lighting, interference can arise due to an incorrect pin sequence, a poor mass connection or corrosion in the connector or junction box. Differences between vehicles, adaptors and wiring also regularly cause faulty signals. In this expert article by one of our technical specialists, we explain more about the causes of trailer lighting failures and what you can do to resolve them.

Would you rather not assemble the wiring yourself? Then take a look at our 7-PIN wiring harnesses for trailers.

Related articles

• 7-PIN connector (12V)

• 7-PIN S connector (12V)
• 13-PIN connector (Jaeger and Multicon West)
• CAN-bus solutions for trailer lighting