Trailer socket
The trailer socket is part of a complete trailer coupling . Its primary purpose is to ensure the operation of the lighting equipment in accordance with the regulations. In Germany , these are set out in the Road Traffic Licensing Regulations (StVZO).
Car
In passenger cars , the connectors carry a nominal voltage of 12 volts. The 13-pin plug connection according to ISO 11446 ( Jaeger system ) has been mandatory since the late 1980s; in old vehicles, the 7-pin plug connection according to ISO 1724 , if necessary also according to ISO 3732 . There are adapters for connecting the two mechanically incompatible systems. There are also the rarer Multicon connectors according to the Dutch NEN 6120. This is compatible with ISO 1724, and also contains the contacts 8 to 13 of the 13-pin connector according to ISO 11446 in a ring.
Mechanical execution
The 13-pin plug connection according to ISO 11446 is operated by means of a bayonet lock. With one hand you have to lift the cap on the vehicle and insert the plug a little with the other. A quarter turn clockwise pushes the plug completely into the socket without having to push the plug against the vehicle. Then you let go of the sealing cap, which lowers it a little and presses the round blank molded onto the plug so that the plug can no longer be twisted and the plug remains in position. To release the plug, lift the cap a little, turn the plug a quarter turn to the left, pull it out completely and let go of the cap.
This principle ensures that the plug is fully inserted and electrical contact is established. Here are contact resistance is reduced and scraped any existing oxide layers on the plug contact pairs. The housing of the plug and socket in most versions is made of fiberglass-reinforced plastic.
The 7-pin plug connection according to ISO 1724 or ISO 3732 as well as the 7 + 6-pin plug according to Multicon are unplugged and plugged in by pulling and pushing. Depending on how tight the individual contacts are, large compressive or tensile forces have to be applied. If the other hand is not used, the carrier plates of the trailer sockets are often bent. The socket cover, whose molded prongs grip behind the plug, serves as a safeguard against unintentional loosening.
The contacts consist of orthogonally slotted contact pins and rigid sleeves. The contact pressure is achieved by the spring action of the slotted contact pins. Due to wear and tear and incorrect operation, however, the spring action diminishes over time. Together with surface corrosion, this can lead to inadmissibly high contact resistances, which can lead to heating and even scorching of the contacts, making them permanently unusable. The housing of the plug and socket is made of fiberglass-reinforced plastic, die-cast metal or sheet steel.
Trailer sockets and contact assignment
The assignment of the individual contacts is regulated by the standards and leaves no room for other types of assignment. The assignment of contacts 1 to 7 is identical for all connector variants. The cable colors are to be adhered to according to the guideline if possible . As a result, other colors or other uses of the existing colors can occur in individual cases.
For the StVO-compliant version, it is sufficient to assign contacts 1 to 8. The other contacts are mainly used for convenience, for example in caravans . The convenience electrical connections are not always used on brand new towing vehicles or retrofit kits.
| Contact | 7-pin plug connection ISO 1724, normal plug connector type N | 7-pin additional connector according to ISO 3732 , additional connector type S | Connector system 7 + 6-pole 12 V according to NEN 6120 Multicon system, compatible pin 7 with plug-type N . The additional annularly arranged contacts 8 to 13 are (at system Multicon spring either as resilient tongues or in a system WeST We lt st ecker ) and socket contacts carried out. The laterally exposed contacts of the WeST socket also allow the insertion of a Multicon spring connector. ISO 11446 |
13-pin plug connection according to ISO 11446 | Conductor cross-section in mm² | informative cable color 7-pin | informative cable color 13-pin | |
|---|---|---|---|---|---|---|---|---|
| image | The additional system differs in its white housing or contact inserts and, compared to the 7-pin plug connection according to ISO 1724, in a changed contact arrangement ( Fig | , | ||||||
| function | Contact no. | Contact no. | recommended conductor cross-section in mm² | Identification color | Terminal designation according to DIN 72552 | |||
| Left direction indicator | 1 | 1 | 1.5 | yellow | L. | |||
| since January 1, 1991 rear fog light, previously permanent plus or not used | 2 | 2 | 1.5 | blue | NS or 54g | |||
| Switch-off contact for the rear fog light of the towing vehicle, connected to contact 2 without a plug | (2a) | (2a) | (2a) | - | - | - | - | |
| Ground of contacts 1, 2 and 4… 8 1 | 3 | 3 | ≥ 1.5 | White | 31 | |||
| Direction indicator right | 4th | 4th | 1.5 | green | R. | |||
| Right tail light | 5 | 5 | 1.5 | brown | 58R | |||
| brake-lights | 6th | 6th | 1.5 | red | 54 | |||
| Left tail light | 7th | 7th | 1.5 | black | 58L | |||
| Reversing light | - | 1 yellow | 8th | 1.5 | pink | RF or ZR | ||
| Continuous voltage + | - | 4 (Green | 9 | 2.5 | orange | 30L | ||
| Charging line for any own battery in the trailer | - | 6 red | 10 | 2.5 | Gray | 30g or 15 | ||
| Since 2004: mass for contact 10, previously: free 1 | - | 7 black | free | 11 | 2.5 | black-and-white | (31) | |
| Since 2004: reserved, previously: trailer detection (with contact 3) | - | - | free | 12 | ≥ 0.75 | - | ||
| since 2004: ground only for contact 9, previously: ground for contacts 9 and 10 1 | - | 3 white | 13 | 2.5 | White-red | 31 | ||
| 1 The ground lines must not be electrically connected to one another on the trailer side. | ||||||||
The permanent voltage connection (9) can discharge the battery of the towing vehicle through loads in the trailer to such an extent that it is no longer possible to start the engine. The other connection (10) called the charging line is different , it only carries voltage when the alternator of the towing vehicle is supplying power. A relay coupled with the ignition is common for this purpose. The charge control connection of the alternator or the oil pressure switch is also suitable for connecting such an isolating relay.
Trailer detection
Trailer detection is not mandatory and cannot be implemented with the permissible, universally designed electrical kits with a flasher relay that must then be replaced and an additional C2 flasher control lamp in the dashboard.
Before 2004, contact 12 according to ISO 11446 was intended as a trailer recognition in the trailer, which was then connected to contact 3 (ground). In fact, this detection was only evaluated by very few trailer control units. For this reason, too, since 2004 with ISO 11446: 2004, contact 12 can no longer be used. It is to be kept free for future use.
Mainly for reasons of comfort, the manufacturer of towing vehicles often carries out trailer detection; the signal can e.g. B. adapt the shift points of automatic transmissions and chassis. Current vehicles therefore have technologies that recognize a trailer with the help of the plugged in. These methods are common:
- There is a switch in the socket that switches off the rear fog lamp in the towing vehicle. This method is to be preferred because of its simplicity and traceability. Disadvantage: A 13-to-7-pin adapter is already recognized as an attached trailer.
- When the ignition is switched on, the trailer control unit connected to the CAN bus of the towing vehicle measures whether light bulbs are connected to the socket outlet. For this purpose, a short current pulse is applied to the line at regular intervals; existing incandescent lamps attenuate the signal due to their characteristic cold resistance. If the indicators, reversing lights and rear fog lights as well as white reversing lights are connected to the socket, the trailer control unit reports the trailer operation via the CAN bus. In this way, for example, driving dynamics properties or gear shift points can be influenced. The disadvantage is that taillights with incandescent lamps must be used; LEDs then require resistors connected in parallel because of the comparatively low power and the lack of positive temperature coefficient .
Rear fog lights switch off on the towing vehicle
When connecting a trailer plug, the rear fog light on the towing vehicle may be switched off. The switch-off is only permitted if the respective switch-off or on again takes place automatically by plugging in or removing the connector for the trailer lighting.
Various methods are possible depending on the design of the electrical system.
- A switch in the trailer socket interrupts the supply to the rear fog light on the towing vehicle when a plug is inserted into the socket. The corresponding contact on the socket is usually labeled 2a or 2b.
- A switch-off relay, which picks up when there is a corresponding current flow via contact 2 (rear fog light) of the trailer socket, interrupts the power supply to the rear fog light on the towing vehicle with a break contact.
- some commercially available trailer control units detect the presence of a trailer by means of a lamp resistance test and thus deactivate the rear fog light on the towing vehicle.
Each variant can involuntarily be operated incorrectly. If an adapter remains e.g. B. from 13 to 7 pole, when not in use in the socket, according to variant 1 the rear fog light is deactivated even without a trailer. According to the legally binding installation instructions, each adapter must be removed when not in use. The installer has to instruct the customer accordingly. With variants 2 and 3, trailers with a rear fog light using LED technology that is not designed for the purpose have the option of not switching off the rear fog light on the towing vehicle.
adapter
Adapters are commercially available for using seven-pin plugs on thirteen-pin plug connections. It is sufficient to connect through contacts 1 to 7, which are assigned identically in both connector systems. Adapters without an intermediate cable, in which the bayonet sleeve of the thirteen-pin plug connection and the lid hinge of the seven-pin plug are connected to one another, are also called “short adapters”.
Although it has not been described in the current standard since 2004, trailer detection contact no.12 can be connected to ground contact no.3 in the 13-pin plug or adapter to 7-pin socket. The aim is to deactivate the distance warning device installed on the towing vehicle when reversing and the fog light.
Furthermore, when using an adapter from a 7-pin connection on the towing vehicle to a 13-pin connection on the trailer, the permissibility must be observed. By using the adapter, the connections for the reversing lights of the trailer cannot be provided, which since January 1, 2011 according to European law is only permitted for trailers up to 750 kg gross vehicle weight.
The reversing light must also work for all trailers on which a reversing light has been properly installed. This applies if a 13-pin trailer connector is available and the reversing light has been electrically connected at the factory.
Trucks, tractors
Connectors that carry a nominal voltage of 24 volts are common for trucks or tractors.
- ISO 1185 : Plug devices for the electrical connection of towing vehicles and trailers - 7-pin plug device type 24 N (normal) for vehicles with 24 V nominal voltage
- the white, 7-pin trailer plugs according to ISO 3731 : plug devices for the electrical connection of towing vehicles and trailers - 7-pin plug devices type 24 S (additional) for vehicles with 24 V nominal voltage
- the ISO 7638 , which describes the plug-in devices for braking systems and braking systems of vehicles with a 24 V rated voltage.
- ISO 11992 : Exchange of digital information about electrical connections between towing vehicles and trailers
- ISO 12098 : Plug devices for the electrical connection of towing vehicles and trailers - 15-pin plug device for vehicles with 24 V nominal voltage
In the case of trucks or tractors, there may be several types of plugs in parallel or versions for 24 volts or 12 volts. The versions for 12 volts correspond to those for cars.
Individual evidence
- ↑ STVZO §53d rear fog lights , paragraph 6