7-PIN type S connector 12V

Updated: 13/01/2026
By: Kevin van Mierlo

The 7-PIN Type S connector is an outdated plug standard that was used in the past alongside the 7-PIN Type N connector. Together, these connectors provided the complete electrical control of caravans and other towed vehicles at a time when functions were not yet combined in one connector .

Today, the 7-PIN Type S connector is no longer used in new construction or modern conversions. This connector was formerly used as a supplement to the 7-pin Type N connector for additional functions and has been functionally replaced by the 13-PIN connector.

While the Type N connector was used for basic lighting, the Type S connector was used for additional functions, such as:

reversing lights
constant power supply
battery charging while driving

This system was defined in the ISO 3732 standard. In current practice, the Type S connector is no longer used in new construction or modern conversions. The functions of both Type N and Type S were later brought together in the 13-PIN connector (ISO 11446), which has since become the standard. The Type S connector is still only found on older caravans and existing installations.

Wiring diagram 7-PIN connector type S (12 V)

The Type S connector had a different function assignment than the Type N connector, despite both being 7-PIN connectors. This made the connectors not interchangeable.

PIN	Function	Colour
1	Battery charging current	Grey
2	Free (optional)	Black
3	Mass for PIN 1	White
4	Free (optional)	Green
5	Reversing lights	Blue
6	Mass for PIN 2 (constant current)	White
7	Constant power supply	Red

Because the pin assignment differed from that of the N connector, confusion could lead to interference or damage to connected equipment.

When was the 7-PIN type S connector used?

The 7-PIN Type S connector was mainly used in combination with the Type N connector, on vehicles and semi-trailers with two separate connections. Common applications were:

older caravans with refrigerator or battery operation
Semi-Trailers with reversing lights before the introduction of the 13-PIN connector
motorhomes and vintage vehicles with separate power circuits

In newer vehicles and semi-trailers , this system has been almost completely replaced by the 13-PIN connection.

CAN-bus problems with modern vehicles

When connecting an older semi-trailer with N+S connections to a CAN-bus vehicle, interference may occur:

LED lighting does not work or gives error messages
Constant current supply is not recognised
Battery does not charge while driving

Take a look at our CAN-bus solutions or read the article:
Fix CAN-bus interference with LED lighting

Frequently asked question

Why have N and S plugs been replaced by 13-PIN connectors?

The double plug solution was error-prone and cumbersome. Therefore, with the introduction of ISO 11446, a single, safe and waterproof 13-PIN connector with integrated N and S functions was chosen.

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Kevin van Mierlo

Lighting expert at TRALERT® - Kevin tests lighting and finds out everything about legislation. He can tell you all about it.

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