Plugs and sockets for trailers and caravans
7-pin plugs and 13-pin plugs play a major role in trailer electrics. These caravan plugs provide a secure connection between trailer, caravan and towing vehicle.
Vehicles with a towing device are equipped with a 13-pin socket. The rear fog light has been mandatory for trailers since 1.1.1991, so the last free pole of the previous 7-pin plug connection has been occupied. Continuous current in the vehicle is no longer possible. That is why there is the 13-pin plug, here you have additional connection possibilities with a 13-pin plug connection:

•     Reversing light
•     Continuous current for caravan
•     Charging line for an additional battery or for lights in the trailer etc.

13-pin to 7-pin or 7-pin to 13-pin, adapters allow any combination between 7- and 13-pin equipped vehicles and trailers. The attachment points are identical for 7-pin and 13-pin connectors.
When buying your trailer plug or trailer socket, look for high-quality contacts with surface finish and a bayonet lock, so that your trailer electrics have a long service life.
Carbest trailer sockets are temperature resistant from +100° to -40°C, dustproof and waterproof.

Trailer electrics - brief overview
The articles for the trailer electrics are mostly identical for caravans, motor homes, commercial trailers and boat trailers. The trailer electrics on older trailers are matched to 7-pin cables. The newer trailers have 13-pin cables and sockets. It usually makes sense to carry the appropriate adapters between the trailer and the towing vehicle, as the standards are often not identical. The most convenient are the so-called short adapters. For more than 10 years, all new vehicles have been equipped with 13-pin trailer sockets. This also allows reversing lights and other additional functions to be transferred to the trailer. However, trailer couplings with 7-pin trailer sockets and trailers with 7-pin trailer plugs are still in use on many older vehicles. For a few years there was also competition between different trailer systems. This is now mostly history.

7-pole plugs, what is where?
7-pole plugs work with Ø 1.5 car cables. The assignment is as follows:
        1 - Left indicator (yellow)
        2 - Rear fog light (blue)
        3*- Ground (white)
        4 - Turn signal right (green)
        5 - Taillight right (brown)
        6 - Brake light (red)
        7 - Taillight left (black)
*The earth wires must not be connected conductively.

Assignment of the 13-pole plugs
13-pin plugs work with Ø 1.5 car cables and Ø 2.5 for charge, earth and continuous positive.
The pin assignment is as follows:
        1 - indicator left (yellow), 2 - rear fog light (blue), 3*- ground (white),
        4 - indicator right (green), 5 - tail light right (brown), 6 - brake light (red),
        7 - taillight left (black), 8 - reversing light (grey), 9 - steady plus (+) (brown/blue),
       10 - charging line (+) (brown/red), 11 and 12 - not assigned, 13* ground pole 9-12 (black/white)
*The earth wires must not be connected conductively.

The WeSt plug or Multicon world plug
The 13-pole Multicon-WeltStecker (WeSt) still fits into 7-pole junction boxes, but no longer into the current 13-pole sockets (Jäger system). Multicon plugs are plugged in and unplugged by pulling and pushing. The western plug is held in place by moulded prongs and plugs. The WeSt plug is now only rarely used as a caravan plug or trailer plug. Caravan plugs with a waterproof and dustproof bayonet lock are preferred.

You find motorhome plugs here.