Connecting a trailer socket and a towbar for a car or truck, color scheme, pinout

A towbar socket is a device necessary for connecting various signals and ensuring the functionality of the electrics on the trailer: brakes, turn signals, parking lights, license plate lights, etc.

Below we will look at the main types of sockets, talk about connection diagrams and pinout features. We will pay special attention to the purpose of the electronic matching unit and the nuances of connecting the socket.

As an example, we will give the principle of connecting the device to a Chevrolet Niva, a LAV boat trailer, a VAZ-2110 and a number of other vehicles.

Types of trailer sockets

When choosing a socket for a passenger car, pay attention to the types of products.

There are two types on sale (according to the number of cores):

Seven-core (7 PIN). Designed to output external lighting sources and is used for standard cargo trailers. Such a socket, in turn, can be European or American (they differ in connectors). The peculiarity of the European circuit is that all seven wires are involved in it.
13-wire (13 PIN). Unlike the previous type, additional connectors are used here to allow you to connect a caravan trailer and ensure the functionality of all lighting and additional equipment (refrigerator, battery charger, etc.). So, to charge the battery, there is a separate conductor, which goes from the machine’s power source to the towbar socket and is protected by an individual fuse insert.

The 13-wire socket has more functionality and is suitable for many cars from the United States or the EU. But purchasing it will cost a lot, and connecting it will require a higher level of skill.

Sometimes situations occur when the car has a 7-pin socket and the trailer has a 13-pin socket (or vice versa). This is not a problem, thanks to the availability of adapters from 13 to 7 or from 7 to 13.

Pinout of 15 pin connector

This type of connector for connecting trailers and semitrailers is an accepted standard for tractors from almost all manufacturers, including American ones. Considering the requirements for trailers of this class, a standard 13-pin connector is not suitable for powering and controlling their electrical equipment.

American connecting chips

Many American standards differ from European ones, and trailer hitch socket pinouts are no exception. Here are two types for your reference: 7 and 4 pin connectors.

Connection diagrams (pinout)

When studying the connection diagram for a trailer socket and a car's towbar, it is important to focus on the current GOSTs and rules. They indicate the requirements of government agencies to avoid errors when connecting and operating devices, as well as when checking the electrical connection diagram.

What GOST 9200-76 says

One of the main documents positioning the connection of 7-pin connectors for cars and trucks, as well as tractors, is GOST 9200-76. It was approved and put into operation on January 19, 1976 and is still in effect.

The standard complies with the following ISOs:

1185-75.
3731-80.
1724-80.
3732-82.
4091-78.

Before the advent of GOST 9200-76, the document GOST 9200-59 was in force, but with the advent of new rules it became invalid.

The following types of sizes are considered here:

24 N and 24 S for 24 V voltage;
12 N and 12 S for 12 V voltage.

At the request of the consumer, the use of 12N is allowed on car tractors, as well as trailers and semi-trailers with a voltage of 24 V.

Connector Features:

24 N is equipped with a large socket for 1 contact and 6 small pins. The inner diameter of the 1st contact must be such as to provide the required disconnection force.
24 S also comes with one large 1st contact and 6 smaller ones.
The 12 N has four sockets (pins one, three, four, and six), as well as three spring-loaded pins—pins two, five, and seven. The diameters of the pins must be such that they fit into the plug sockets and provide the necessary force.
12 S provides a special design. This socket is equipped with four sockets (one, three, four and six), one recessed 7th socket (3 mm deeper), as well as a pair of spring pins (second and fifth contacts).

Diagrams and pinouts of 24 N connectors.

Socket, type 24N for rated voltage 24 V

Plug, type 24N for rated voltage 24 V

24N pin assignment

Diagrams and pinouts of 24 S connectors.

GOST 9200-76 pays special attention to technical requirements. In particular, the connector must provide a stable connection at currents up to 40 A. It is important that the pins and sockets do not rotate in their places, and their designation must be applied in a reliable way to ensure good readability.

The permissible temperature rise should not be more than 45 degrees Celsius when the load current is 25% more than the rated one.

Pinout

When connecting the trailer socket and towbar, it is necessary to take into account the subtleties of the pinout. Let's consider each option separately.

7 PIN

7-pin sockets for trailers are used in Russia and Europe. Type - 12 N, ISO 1724.

The designation of the legs is as follows:

Left turn signal (L). Yellow, 1.5 sq. mm.
Rear fog lights or +12 V (54G). Blue, 1.5 sq. mm.
Grounding (“minus”) White/gray, 2.5 sq. mm.
Turn signal right (R). Green, 1.5 sq. mm.
Lamp for illuminating the license plate and marker on the right (58R). Red, 1.5 sq. mm.
Brakes - stop light (54). Red, 1.5 sq. mm.
Left dimension (58L). Black, 1.5 sq. mm.

Simplified diagram.

In the case of the American version of the 7 PIN socket, the placement of the contacts is slightly different. Here the reverse contact connector has been changed, and there is no section on left and right dimensions. In a number of cars from the USA, the dimensions and STOP signals, which run on the same wire, are not separated.

Alternatively, you can assemble a “Russian” circuit. Its peculiarity is that there may be no wire on the PTF, or there will be only one, connected to the 7th pin of the plug. In this case, the 5th contact is not used or is short-circuited by the 7th.

One example of a 7-pin device is the ATE-05 metal socket from the manufacturer Airline. This is the most durable product for a towbar without an elastic boot.

13 PIN

When choosing a 13-pin socket (ISO 11446), the number of connectors is larger, so you need to be more careful when connecting.

Let's look at the main elements:

Left turn signal (1/L). Yellow, 1.5 sq. mm.
Rear fog lamp (2). Blue, 1.5 sq. mm.
Ground connector for terminals one through eight (3/31). White, 2.5 sq. mm.
Right turn signal (4/R). Green, 1.5 sq. mm.
Right side marker and license plate light (5/58-R). Brown, 1.5 sq. mm.
STOP signal lamp (6/54). Red, 1.5 sq. mm.
Dimensions on the left and license plate illumination (7/58-L). Black, 1.5 sq. mm.
Reverse lamp (8). Pink, 1.5 sq. mm.
Constant voltage at 12 V and 35 A (9). Orange, 2.5 sq. mm.
Voltage 12 V and 35 A (supplied after turning the key in the ignition), (10). Gray, 2.5 sq. mm.
"Mass" (11). Black and white, 2.5 sq. mm.
Signal conductor, reserve (12). Light grey, 1.5 sq. mm.
Ground for the ninth terminal (13). Red-white, 2.5 sq. mm.

Having before your eyes the pinout of the trailer and towbar sockets, you can easily make connections and carry out an electrical inspection (in case of a malfunction).

In Europe, 7-pin (ISO-1724) and 13-pin (ISO-11446) connectors are in demand. As you can see from the pinout above, the 13-pin version gives more options and has better protection against water and dirt.

The connectors work on 12V systems, but there may be exceptions for the 7-pin connector. They often operate on 6 and 24 V. Thus, cars and trailers with 6-pin systems can use a 7-5 pin connector.

7 pin towbar socket

So, although there may be different types of connections on a car, today the most common solution is a connection diagram where the plug has 7 pins. This is the so-called 7 pin Euro connector. By the way, even on cars with electronic circuits and control units, there is a smart connect type option that coordinates the operation of the car’s wiring with the trailer.

If we talk about the Euro connector mentioned above, this solution is used for the vast majority of passenger car trailers. It is important to take into account that the receiving part, as well as the mating part, have two types of sockets, that is, a “male” socket and a “female” socket. This solution is necessary for safety in order to eliminate possible errors when connecting such connectors. Also, the location of the sockets prevents short circuits.

Similar connectors can be purchased at a car dealership or car market. To make the connection, multi-core copper cables that have wires of different colors are usually used.

Let’s also add that in order for the connectors to last as long as possible, the contacts need to be coated with lithol. It is also recommended to always use protective plastic caps to prevent water and dirt from getting inside when the trailer is disconnected.

Let's move on. To synchronize the light signals, you need a special pinout of the trailer socket (usually 7 pins), as well as connecting such a socket to the car wiring. It turns out that the car has a towbar socket (trailer socket), into which the trailer wiring plug is inserted.

It is better to place the socket in various openings for replacing lamps, since such areas provide the most convenient access to the sockets. Let’s also add that if the towbar itself has a socket with signals output to it, you can purchase a 7-pin plug. This is the standard towbar connection diagram.

If there is no such socket, then you should resort to a universal connection, when the wiring can be connected directly to the signal circuits, but only on cars without a BC. The wires from the connector are also connected to the circuits for the tail lights. Let's look at the connection in more detail.

Why do you need an electronic matching unit?

Not in all cases it is possible to simply connect the sockets of the towbar and trailer. If the machine has complex electronics, a matching unit will be required.

Its use allows you to avoid errors when testing the operation of lighting equipment and vehicle electrical systems.

In addition, the matching unit is an invariable thing when it is necessary to transmit a signal using a multiplex bus.

The connection diagram is as follows:

Signals from the car are sent to the matching unit.
The latter processes the information.
If there are no conflicts, the signal is transmitted to the trailer of the car or truck.

For correct operation, the unit must be connected to the battery and the wires must be connected correctly (taking into account the pinout).

The connection diagram is shown below.

About installation methods when connecting a tow hitch

The presence of electronics in the vehicle control system allows the use of an electronic coordination unit in the installation of the electrical system for signaling and trailer control. It will monitor and test control signals through a multiplex program.

If the current in the circuits increases, the device will generate an error in signal transmission. Installation and connection to the connector on the tow mechanism is carried out according to a special program with the connection of a matching device in the circuits.

During installation, it is necessary to use a device in the circuits of the machine that will transmit control signals through the matching unit to the towed mechanism, and not through the detachable part in the trailer.

What is needed to connect

Before connecting the trailer socket, you need to prepare and buy the necessary material in advance.

The package includes the following equipment:

Socket cover for tow bar. Please note that there is a cover equipped with a rubber seal. When purchasing, inspect the product for the fit of all casing elements and for the absence of loose housing or contact connections. Pay special attention to the condition of the threaded connection and the fastening of screws to the terminals.
Wire (one core) with a cross-section of 1.5 sq. mm or more. When purchasing, check the possibility of using it in the electrical wiring of a vehicle.
Corrugation made of metal or polypropylene. Used to insulate wire harnesses and protect against mechanical damage. The average length is up to 2.5-3.0 meters. Immediately take 20-30 plastic clamps to secure the harnesses.
Connecting blocks. When choosing, give preference to a model with sockets in which fuses can be installed.
Tools: set of wrenches, drills and bits, screwdrivers, soldering iron, electrical tape.

The specified equipment is usually sufficient for installation work. If something is missing, the scarce elements can be purchased separately.

Features of connecting trailers Skif-M1, Skif-M2, MZSA and others

When connecting SKIF trailers, you need to be careful, because the pinout in them is somewhat different from the 7-pin circuit according to GOST 9276 and ISO 1724.

Thus, on the second terminal of the Skif-M1, produced from 1981 to 1987, and Skif-M2, produced from 1987 to 1993, the “plus” of the battery is located, and not the rear fog lamp.

Skif-M trailer electrical diagram

Electrical diagram of the Skif-M1 trailer

Electrical diagram of the Skif-M2 trailer

In addition, on MZSA trailers, the dimensions are connected only to the 7th contact. This is done for convenience, so that if necessary you can connect to an old domestic car.

The presence of a “+” battery is a big plus when camping, because it can be used to connect lighting. The designation of the contact group has also changed. Instead of the usual Arabic numerals, Roman numerals are given here.

If we talk about earlier versions of Skif-M, they have more differences.

The following scheme was used here:

I—STOP signal;
II - left turn signal;
III — turn signal indicator light;
IV - right turn signal;
V - “plus” of the battery;
VI — rear dimensions and license plate lights;
M is mass.

The circuit provides a matching block that relieves the car's turn signal relay.

To operate this element, constant power is required, supplied through the fifth contact from the battery through the outlet.

The old connectors did not separate the side light contacts and they were supplied only through the seventh contact, and the second was considered a spare one.

A lamp was provided there that allowed you to monitor the operation of the trailer and its turn signals.

When connecting an old trailer to a modern type socket, the turn signal on the trailer hitch will only flash when the lights are on. In addition, the fog light (on some models) and the warning light on the dashboard may flash.

In the case of MZSA trailers, nothing comes of the fifth signal. Therefore, if after connection the lights on the tow hitch do not light up, the reason, as a rule, is that the signal is output to the fifth contact, but there will be no signal on the seventh.

A number of trailer manufacturers in the Russian Federation, when installing a reversing lamp, connect it to the fifth terminal, leaving the dimensions with the seventh contact connection.

LAV boat trailer pinout

Of particular interest is the pinout of contacts in LAV brand trailers. Let's highlight the features of contacts:

Left turn signal.
Rear PTF.
Weight.
Right turn signal.
Reversing lamp.
STOP signal.
Side and contour lights, room lighting.

Knowing the features of the contact group will help you accurately connect the trailer and towbar socket.

Connecting a VAZ 2110 trailer socket

The VAZ 2110 uses a trailer socket made according to the 12 N, ISO 1724 standard.

There are seven contacts here: two turn signals (first and fourth), fog light (second), ground (third), rear lights and right side lights (fifth), brake light (sixth) and left side lights (seventh).

As in previous cases, wires with a cross-section of 1.5 square meters are used for all contacts. mm, except for the “ground”, which goes to 2.5 square meters. mm.

Niva Chevrolet

When connecting a trailer socket to a Niva Chevrolet, you can use a wiring harness with a trailer hitch (tow hitch) and European accessories 0183 for the specified Avato model. Article - 00001-75045552-00-0.

In addition, this harness is suitable for connecting trailers of other cars with a 7-pin connector, avoiding the use of a bundle of wires with five + two wires.

Important information

The definition of a connector can be described as a combination of plugs and sockets that are connected after the trailer is attached to the hitch.
Here it is important to pay attention to who is the manufacturer of the towing device and the trailer itself. In some cases, the number of contacts they have is different. Our standard pinout includes 7 contacts. This is a European and domestic manufacturing principle. But if you have an American car in front of you, be so kind as to understand the 13-pin connector. It is also important that the contacts on plugs and sockets are counted differently.

If you need to connect different types of trailers and vehicles, you will need to use a special connection block or adapter. Alternatively, you can make adjustments to the pinout. But this will require deeper knowledge of auto electrics, as well as a detailed study of the design of the car itself.

Connecting a trailer socket to a KamAZ truck

Owners of KAMAZ trucks often ask what type of socket can be used for a trailer.

The main option is a plug device type PS 325-100 for 24 V. The product is designed to transmit electrical signals to side lights, brake lights, turn signals and other elements. They come with 7 and 15 cores.

In this case, 7-core models are conventionally divided into two types - N and S. The first type is very similar to the other models, and the S-type has the appearance of an empty tube.

Pinout:

Mass (Part 4), white.
Left size (G.52), black.
Turn signal on the left (K.75), yellow.
Brakes (3.57), red.
Turn signal on the right (P.74), green.
Right gauge (Kch. 52), brown.
Not involved. You can connect a reverse gear or a portable lamp. Blue.

As an analogue, you can use a 24 V socket manufactured by BAAZ). Its pinout is the same, only the manufacturer is different.

When choosing the original PS 325, pay attention to the following points:

When turning the product over, the lid should not open. It is optimal if it is well spring-loaded and opens only with force from the user.
The pins inside should not dangle.
In the fake, the holes at the base are very small. You can check this using a special wire crimper.
Pay attention to the quality of the internal thread and material. It is very difficult to screw a screw into a fake socket. In addition, the product itself is made of aluminum.

Knowing these points allows you to distinguish a fake from an original and avoid wasting money.

Vehicle installation

Basic procedure

First, remove the bumper and cut off the lugs. Drill holes if necessary and weld the fasteners.

Here's how to connect a trailer towbar to a car:

We will need an inspection hole on the overpass or in the garage into which we drive our vehicle.
Now we turn off the power from the mains by disconnecting the negative terminal from the battery.
Installing towbars will require removing everything from the trunk and removing its upholstery.
The device itself must be attached to the place where it is planned to be attached and the necessary markings must be made.
At the attachment point, holes are drilled on both sides with a drill, which are best treated with an anti-corrosion agent to extend service life;
As the photo for this article suggests, we can tighten the hitch using nuts, washers and bolts, as well as a suitable size wrench.
Now you need to remove the load from the car frame and provide a more reliable fastening. To do this, we make a couple of holes at the bottom of the side member and from the inside of the luggage compartment with the installation of reinforcing linings.
Tighten all the necessary bolts with wrenches.

Fastening to the car frame

Using the connection diagram

A ready-made towbar, as a rule, already has all the necessary holes for fastening, which is taken care of by the towbar manufacturers. Now we can start connecting the hitch.

We cannot do without an outlet that connects the electrical wiring of the car and the trailer. The towbar socket diagram is usually included in the kit. As for the electrical equipment of the coupling device, it consists of a plug socket with a set of wires. The color of the wiring may not match the color of the wires in the photo.

Bolted to the bracket, the socket is connected to the main wiring. When connecting, you need to look at the colors of the wires according to the diagram. You need to connect it to a standard connector, which can be 7-wire or 13-wire (only on foreign cars).

Car installation

Below are instructions with which we can connect the towbar to the electronics of the car:

We will need a hole located in the bottom of the trunk to connect the socket to the rest of the wiring. In the case where the coupling device is made independently, you will have to drill the holes yourself. Consider the location of your future location;
After the socket is installed on the towbar, we will stretch the wire through the hole in the trunk and connect it to the socket.

The connection diagram for Largus can be of some help if you are the owner of this particular model

During connection, the wiring must be connected in such a way as not to confuse the order. If the number of wires does not match, purchase an adapter for the socket. A special tube into which you need to pass the assembled wiring kit will help protect the electrical package from external damage and short circuits;
Secure the wires to the trunk walls and carefully cover them with upholstery.
You can connect the trailer, check how high it is from the ground, and whether its brake lights, turn lights, and running lights are working.

The towbar can be installed on any car. Installation points are indicated in the product instructions

Electrical work

Electrical equipment for towbars is a different area than the manufacture of towbars. When choosing a device, select it in such a way that it does not cover the vehicle’s license plate. Sometimes you have to cut off part of the bumper for this purpose.

The photo shows the installation process on a ninth generation VAZ

The opposite situation may also arise when there is no need for a coupling device. For example, the owner purchased a vehicle with a tow bar installed, but wants to remove it. In this case, you will need to work backwards to disconnect all the wiring that is assembled together.

In the same way as we connected the towbar socket, we will disconnect it in the same way.
Mechanically it can be dismantled using a special key.
If it is not there, then you will have to cut off the bolts or welds. It is better to entrust such work to experienced mechanics and electricians.