What is the pin configuration of the trailer socket, and what causes the lights to fail?
7-pin plug (Type N, ISO 1724) — the older standard:
| Pin | Terminal | Colour according to DIN | Function |
|---|---|---|---|
| 1 | L | yellow | Left direction indicator |
| 2 | 54G | blue | Rear fog light |
| 3 | 31 | white | Ground |
| 4 | R | green | Right-hand direction indicator |
| 5 | 58R | brown | Right-hand rear light |
| 6 | 54 | red | Brake light |
| 7 | 58L | black | Left rear light and number plate light |
13-pin plug (ISO 11446) — current standard, with additional functions and separate earth connections:
| Pin | Colour according to DIN | Function |
|---|---|---|
| 1 | yellow | Left direction indicator |
| 2 | blue | Rear fog light |
| 2a | — | Switch for rear fog light on the vehicle |
| 3 | white | Earth (circuits 1–8) |
| 4 | green | Right-hand direction indicator |
| 5 | brown | Right-hand tail light, side marker light and number plate light |
| 6 | red | Brake light |
| 7 | black | Left tail light, side marker light and number plate light |
| 8 | orange | Reversing light |
| 9 | red, 2.5 mm² | Direct power supply (terminal 30) |
| 10 | black-red | Battery charging lead |
| 11 | green-brown | Earth for charging cable |
| 12 | — | not assigned |
| 13 | white, 2.5 mm² | Earth for circuit 9 |
The numbering stamped on the plug and socket is binding — for cable sets with different numbering, this applies rather than the wire colours.
Adapter: Converting from a 13-pin connector on the vehicle to a 7-pin connector on the trailer is straightforward. Conversely, only the basic functions will work — the reversing light, constant power supply and charging circuit are missing, as there are no corresponding wires in the 7-pin system. Disconnect the adapter when not in use, otherwise the contacts will corrode.
If the lighting fails, it is usually not the bulb that is faulty, but the connection to it. Check in the following order:
- Contacts in the plug and socket — corrosion is the most common cause. Clean, dry and apply contact cleaner.
- Earth — is the connection to the frame secure and rust-free? If several functions fail at the same time, the earth connection is almost always to blame.
- Cables on the drawbar — this is where cables most often chafe through, often directly behind the plug.
- Bulbs and lights — only once everything else has been checked.
Conversion to LED: Lights must have a valid approval mark. After conversion, the trailer monitoring system in the towing vehicle may no longer be able to detect the trailer because the current flow is too low — in which case a suitable control unit will help.
Spare parts: electrical components, plugs and cables, as well as lighting.
