Connection diagram for 4-pin relay. Standard automotive relays

All the main electrical circuits and modifications for connecting the liquid cooling fan (CO) in VAZ cars of various models are provided. What is the essence of VO’s work? An electric motor with an impeller on a shaft is installed inside a rectangular metal frame, with which it is attached to the back of the radiator. When voltage (12 V) is applied to the contacts of the drive, it begins to work, rotating the blades and creating a directed stream of air, which, in fact, cools the antifreeze or antifreeze.

If the cooling fan does not work, do not rush to contact a car service. You can determine the cause of the malfunction yourself. Moreover, for this it is not at all necessary to have special skills - just study the reference material from website and follow the instructions to check/replace it.

Connection diagram for the VAZ 2104, 2105 and 2107 cooler

radiator fan
temperature sensor (located on the bottom of the radiator)
mounting block
ignition relay
egnition lock

A - to contact “30” of the generator.

Electric cooling fan VAZ 2106

electric motor switch sensor;
fan motor;
motor start relay;
main fuse box;
ignition switch;
additional fuse box;
generator;
accumulator battery.

Fan connection 2108, 2109, 21099

Until 1998, on cars with the old mounting fuse block 17.3722 (finger type fuses), relay 113.3747 was included in the fan circuit. After 1998 there is no such relay.

Also, before 1998, the TM-108 switching sensor was used (the closing temperature of its contacts is 99±3ºС, the opening temperature is 94±3ºС), after 1998 the TM-108-10 with similar temperature ranges or its analogues from different manufacturers. The TM-108 sensor only works in conjunction with a relay; the TM-108-10, reinforced for high current, can work both with and without a relay.

Scheme for switching on the engine cooling fan on a VAZ 2109 with mounting block 17.3722

Fan motor
Motor start sensor
Mounting block
Ignition switch

K9 - Relay for turning on the fan motor. A - To terminal “30” of the generator

Scheme for switching on the engine cooling fan on a VAZ 2109 with mounting block 2114-3722010-60

Fan motor
Sensor 66.3710 for turning on the electric motor
Mounting block

A - To terminal “30” of the generator

Connection diagram for VO VAZ 2110

The circuit diagram for switching on the cooling fan of the VAZ 2110 on carburetor and injection cars is different. On cars with a carburetor engine, a thermobimetallic sensor TM-108 is used for this, and on cars with an injection engine, control is carried out by a controller.

Diagram for 2113, 2114, 2115 injector and carburetor

Where is the fan relay located?

4 – electric fan relay;
5 – electric fuel pump relay;
6 – main relay (ignition relay).

Attention: the order of the relays and fuses can be arbitrary, we are guided by the color of the wires. Therefore, we find a relay from which comes a thin pink with a black stripe wire coming from the main relay (pin 85*) (not to be confused with the thin, red with a black stripe wire coming from the controller) and a thick power white with a black stripe wire (pin 87) (white and pink wires we need), this is the fan relay.

If the cooling fan does not work

To drive the fan, a DC electric motor with excitation from permanent magnets ME-272 or similar is installed. Technical data of the electric fan and fan switch sensor:

Rated rotation speed of the electric motor shaft with impeller, 2500 – 2800 rpm.
Electric motor current consumption, 14 A
Sensor contact closure temperature, 82±2 degrees.
Sensor contact opening temperature, 87±2 degrees.

The cooling system fan may not turn on due to:

electric drive malfunctions;
blown fuse;
faulty thermostat;
a failed thermal sensor for turning on the cooler;
faulty VO relay;
broken electrical wiring;
faulty expansion tank plug.

To check the VAZ fan electric motor itself, we apply 12 V voltage from the battery to its terminals - a working motor will work. If the problem is with the fan, you can try to repair it. The problem is usually the brushes or bearings. But it happens that the electric motor fails due to a short circuit or break in the windings. In such cases, it is better to replace the entire drive.

The BO fuse is located in the mounting block of the car's engine compartment and is designated F7 (20 A). The test is carried out using a car tester turned on in probe mode.

In a car with a carburetor engine you need to check the sensor - turn on the ignition and short-circuit the two wires going to the sensor. The fan should turn on. If this does not happen, the problem is definitely not with the sensor.
For injection cars it is necessary to warm up the engine to operating temperature and disconnect the sensor connector, disconnecting it from the vehicle’s on-board network. In this case, the controller must start the fan in emergency mode. The electronic unit perceives this as a failure in the cooling system and forces the fan drive to operate in constant mode. If the drive starts, the sensor is faulty.

Replacing an electric fan in a car

We park the car on a flat surface and immobilize it with the parking brake.
Open the hood and disconnect the negative terminal.
Using a 10mm wrench, unscrew the fastenings of the air filter housing.
Using a screwdriver, loosen the air duct clamp on the air flow sensor and remove the corrugation.
We unscrew the screws securing the cover of the air filter housing and remove the filter element.
Using a size 8 wrench, unscrew the air intake mount and remove it.
Using a 10mm wrench, then an 8mm wrench, unscrew the nuts securing the fan casing around the perimeter (6 pieces in total).
Disconnect the wire block on the fan connector.
Carefully remove the fan casing along with the drive.
Using a 10mm wrench, unscrew the 3 bolts holding the electric motor to the casing.
We put a new one in its place.
We install the structure in place, fix it, and connect the connector.
We carry out further installation in the reverse order.

Control circuit modernization

The cooling fan on the top ten turns on at a temperature of 100-105°C, whereas normal operating
The engine temperature is 85-90°C, so the fan turns on when the engine overheats, which naturally has a negative effect.

This problem can be solved in two ways: adjust the switch-on temperature in the “brains” or make a button. We'll focus on the second one. Turning on the fan from the button is very convenient: if you get into a traffic jam - turn it on, leave - turn it off, and no overheating.

A button for selecting the fan operating mode was installed in the cabin (always off, constantly on, automatically turned on via a sensor) - this “tuning” is not mandatory, but will be a very useful addition.

There will be a large current at relay contacts 87, 30, on the wire from the battery to the fuse and the fan ground, and therefore we must use wires there with a cross-section of at least 2 mm, otherwise the thinner wire will not withstand it and will burn out.

Video - connecting and checking VO

The design and circuit diagram of the radiator fan may differ not only depending on the make of the car, but also on the year of manufacture and model configuration. Let's consider not only the principle of operation, but also the connection option with the possibility of forced activation of the cooling system fan (VSO).

Cooling system design features

Depending on the design features, the fan can be turned on in 3 ways:

using a power sensor for activation of the VSO. This sensor is also called a fan temperature relay, since the power contacts of the electric motor pass directly through the sensor. With this scheme, the load on the thermal relay increases significantly, which reduces its service life;
using the fan switch sensor, but now closing the contacts in the temperature switch triggers the relay, through which the power contacts of the cooling fan are connected. This connection method is much more reliable than the previous option;
using an electronic engine control unit. The ECU, focusing on the coolant temperature sensor installed in the engine cooling radiator, supplies power to the VCO through a relay. A resistive temperature sensor is used as a meter. It is this switching circuit that is used on the vast majority of modern cars. On cars equipped with air conditioning, one of the electric fans will be controlled by the comfort unit. This is necessary for forced cooling of the condenser when the interior air conditioning system is activated.

Operating modes

When understanding the operating principle and connection diagram of a radiator fan, you should remember that electric motors often have two speed modes. This is implemented in 2 ways:

by adding a resistor to the circuit, which increases the resistance and, as a result, reduces the current. The design uses a two-contact sensor, which, depending on the temperature, powers the electric motor directly or through resistors;
a combination of parallel and series connection. The circuit is used on a car with two fans. They can be connected in series, in which case, according to Ohm's law, they will operate from 6 V, or in series, when 12 V is supplied to each of the VSOs. The modes correspond to low and high speed rotation of the propeller.

Scheme options

Schematic diagram of VSO connection on VAZ 2108, 2109, 21099 (until 1998).

As we can see, the sensor controls the fan relay, which is located in the fuse box. When a certain temperature is reached, the contacts of the temperature switch close, which leads to the flow of current in the electric motor circuit.

Above is a diagram for VAZ 2108, 2109, 21099 cars, but after 1998. As we can see, the power sensor now functions as a relay.

Let's consider a circuit using a resistor to implement two propeller rotation speeds using the VW Passat as an example. The two-position fan power sensor S23, depending on the coolant temperature, closes the contacts directly or through an additional resistance.

DIY connection

Some drivers, warning the engine against malfunction of the radiator fan power supply thermal relay, make a remote button to force the electric motor to turn on. To do this, it is enough to connect a fixed button in parallel to the control output of the relay coming from the sensor, which, when pressed, will close the contact to ground, thereby provoking the operation of the relay. If the car's design does not provide a fan relay, you will have to install it yourself to force cool the radiator.

Under no circumstances should you connect the electric motor directly through the button in the cabin! We also do not recommend connecting the circuit so that after turning on the ignition the electric fan constantly rotates, as this significantly reduces its service life.

To connect, you only need to understand the operating principle of a 4-pin relay and minimal knowledge in installing additional equipment. Be sure to include a fuse of the required rating in the power circuit and place it as close to the power source as possible (read more).

If desired, you can replace the single-position sensor with a two-position one, which, paired with a selected resistor, will allow you to realize a low speed of operation of the VSO. If you have a sufficient level of knowledge in electrical engineering, then you can build a PWM controller to adjust the speed of rotation of the propeller. Controlling the electric fan using a PWM signal will allow you to smoothly regulate and arbitrarily select the rotation speed depending on the temperature load on the engine. There is enough material on the Internet on how to make a PWM controller with your own hands.

. Intermediate electromagnetic relays are used in many electronic and electrical circuits and are intended for switching electrical circuits. They are used to amplify and transform electrical signals; remembering information and programming; distribution of electrical energy and control of the operation of individual elements, devices and equipment units; coupling of elements and devices of radio-electronic equipment operating at different voltage levels and operating principles; in alarm, automation, protection circuits, etc.

An intermediate electromagnetic relay is an electromechanical device that can switch electrical circuits and also control another electrical device. Electromagnetic relays are divided into relays permanent And alternating current.

The operation of an electromagnetic relay is based on the interaction of the magnetic flux of the winding and a moving steel armature, which is magnetized by this flux. The figure shows the appearance of the RP-21 type intermediate relay.

1. Relay device.

The relay is reel, the winding of which contains a large number of turns of insulated copper wire. Inside the coil there is a metal rod ( core), mounted on an L-shaped plate called yoke. The coil and the core form electromagnet, and the core, yoke and anchor form relay core.

Located above the core and coil anchor, made in the form of a metal plate and held by return spring. Rigidly anchored moving contacts, opposite which the corresponding pairs are located fixed contacts. Relay contacts are designed to close and open an electrical circuit.

2. How the relay works.

In the initial state, until voltage is applied to the relay winding, the armature, under the influence of the return spring, is at some distance from the core.

When voltage is applied, current immediately begins to flow in the relay winding and its magnetic field magnetizes the core, which, overcoming the force of the return spring, attracts the armature. At this moment, the contacts attached to the anchor, moving, close or open with the fixed contacts.

After turning off the voltage, the current in the winding disappears, the core is demagnetized, and the spring returns the armature and relay contacts to their original position.

3. Relay contacts.

Depending on the design features, the contacts of intermediate relays are normally open(closing), normally closed(breaking) or changeover.

3.1. Normally open contacts.

As long as the supply voltage is not applied to the relay coil, its normally open contacts are always open close, closing the electrical circuit. The pictures below show the operation of a normally open contact.

3.2. Normally closed contacts.

Normally closed contacts work the other way around: as long as the relay is de-energized, they are always closed. When voltage is applied, the relay is activated and its contacts open, opening the electrical circuit. The pictures show the operation of a normally open contact.

3.3. Changeover contacts.

At changeover contacts with a de-energized coil average the contact attached to the anchor is general and is closed with one of the fixed contacts. When the relay is triggered, the middle contact, together with the armature, moves towards the other fixed contact and closes with it, while simultaneously breaking the connection with the first fixed contact. The pictures below show the operation of a changeover contact.

Many relays have not one, but several contact groups, which makes it possible to control several electrical circuits simultaneously.

There are special requirements for intermediate relay contacts. They must have low contact resistance, high wear resistance, low tendency to weld, high electrical conductivity and long service life.

During operation, the contacts with their current-carrying surfaces are pressed against each other with a certain force created by the return spring. A current-carrying surface of a contact in contact with a current-carrying surface of another contact is called contact surface, and the place where the current passes from one contact surface to another is called electrical contact.

The contact of two surfaces does not occur over the entire apparent area, but only in separate areas, since even with the most careful treatment of the contact surface, microscopic tubercles and roughness will still remain on it. That's why total contact area will depend on the material, the quality of the contact surfaces and the compression force. The figure shows the contact surfaces of the upper and lower contacts in a greatly enlarged view.

Where current passes from one contact to another, electrical resistance occurs, which is called contact resistance. The magnitude of the contact resistance is significantly influenced by the magnitude of the contact pressure, as well as the resistance of the oxide and sulfide films covering the contacts, since they are poor conductors.

During long-term operation, the contact surfaces wear out and can become covered with soot deposits, oxide films, dust, and non-conductive particles. Contact wear can also be caused by mechanical, chemical and electrical factors.

Mechanical wear occurs when contact surfaces slide and impact. However, the main reason for contact failure is electrical discharges, arising when opening and closing circuits, especially DC circuits with an inductive load. At the moment of opening and closing, the phenomena of melting, evaporation and softening of the contact material, as well as the transfer of metal from one contact to another, occur on the contact surfaces.

Silver, alloys of hard and refractory metals (tungsten, rhenium, molybdenum) and metal-ceramic compositions are used as materials for relay contacts. The most widely used material is silver, which has low contact resistance, high electrical conductivity, good technological properties and relatively low cost.

It should be remembered that there are no absolutely reliable contacts, therefore, to increase their reliability, parallel and serial connection of contacts is used: when connected in series, the contacts can break a large current, and parallel connection increases the reliability of the electrical circuit.

4. Electrical diagram of the relay.

On circuit diagrams, the coil of an electromagnetic relay is depicted as a rectangle and the letter “K” with the serial number of the relay in the circuit. Relay contacts are designated by the same letter, but with two numbers separated by a dot: the first number indicates the serial number of the relay, and the second indicates the serial number of the contact group of this relay. If in the diagram the relay contacts are located next to the coil, then they are connected by a dashed line.

Remember. In the diagrams, the relay contacts are shown in a state when voltage has not yet been applied to it.

The manufacturer indicates the electrical circuit and numbering of the relay terminals on the cover covering the working part of the relay.

The figure shows that the coil terminals are indicated by numbers 10 And 11 , and that the relay has three groups of contacts:
7 — 1 — 4
8 — 2 — 5
9 — 3 — 6

Here, under the electrical diagram, the electrical parameters of the contacts are indicated, showing what maximum current they can pass (switch) through themselves.

The contacts of this relay switch an alternating current of no more than 5 A at a voltage of 230 V, and a direct current of no more than 5 A at a voltage of 24 V. If more than the specified current is passed through the contacts, they will very soon fail.

On some types of relays, the manufacturer additionally numbers the terminals on the connection side, which is very convenient.

For ease of operation, replacement and installation of relays, special blocks are used that are installed on a standard DIN rail. The blocks have holes for relay contacts and screw contacts for connecting external conductors. Screw contacts have contact numbering that matches the relay contact numbering.

Also on the relay coils the type of current and operating voltage of the relay winding are indicated.

Let's leave it at that for now, but let's look at Main settings And connection of electromagnetic relays, where we will analyze the operation of relays using examples of simple circuits.

See you on the pages of the site.
Good luck!

Literature:

1. I. G. Iglovsky, G. V. Vladimirov - “Handbook of electromagnetic relays”, Leningrad, Energy, 1975.
2. M. T. Levchenko, P. D. Chernyaev - “Intermediate and indicating relays in relay protection and automation devices”, Energy, Moscow, 1968, (Electrician’s Book, issue 255).
3. V. G. Borisov, “Young radio amateur”, Moscow, “Radio and Communications” 1992

DRLs (daytime running lights) are additional lighting devices installed on a car for use during daylight hours. I would like to emphasize that DRLs are intended to indicate your vehicle in front of other road users, and not to provide additional illumination of the roadway. There is no doubt about the benefits of using DRLs; your car will become noticeable at a distance of several kilometers. This is achieved by using bright LEDs in the DRLs. In this article, I will tell you about the legal aspects of installing DRLs, as well as the various DRL wiring diagrams.

Legislation

Before practicing installing DRLs, I would like to dwell a little on the legal standards for installing DRLs, as well as the rules of their operation.

The very first and basic rule is that unauthorized installation of additional light signals on a car is prohibited. Yes, you are right, you do not have the right to install DRLs on your car if it was not equipped with them by the manufacturer. This will be considered as making changes to the design of the vehicle. For every change in the design of a vehicle, a certificate must be obtained, which in itself is neither quick nor cheap. Otherwise, traffic police officers will issue you a fine, or even take your car to the impound lot.

How so? My neighbor installed DRLs on the Oka and drives calmly! - you ask. He is simply lucky to have loyal traffic police officers who do not pay attention to his DRL - I will answer you.

Once again, unauthorized installation of additional light signals on a car is prohibited if it was not equipped with them by the manufacturer. Therefore, you make any changes to the design of the vehicle at your own peril and risk. It’s a completely different matter if your car’s equipment does not include DRLs, but the more expensive trim levels of your model do have DRLs. In this case, you have the right to install DRL without any approval from the certifying authorities.

The first rule for installing DRLs concerns their location on the car body (see picture). If we briefly describe this figure, we get the following:

DRLs should be installed at a height of 250 to 1500 mm;
The distance between adjacent edges of the DRLs must be at least 600 mm;
The distance from the outer side surface of the vehicle to the nearby edge of the DRL should be no more than 400 mm.

Now let’s briefly go through the rules of operation and use of DRLs:

DRLs should only be used during daylight hours;
It is prohibited to use DRLs in conjunction with side lights, low and high beam headlights, as well as fog lights.

Everything that is not prohibited is permitted. It's that simple. Separately, I would like to dwell on an important point, it concerns the use of DRLs in conjunction with high beam headlights. The rule goes something like this: When the high beam signal is briefly signaled, with the side lights and low beam headlights turned off, the DRLs should not turn off. Let me break it down: you are driving with your headlights and side lights turned off, your DRLs are on, when you signal with your high beams to an oncoming car that you are approaching a traffic police post, your DRLs should not turn off.

Just? I also think that there is nothing complicated here. Knowing the legislation and rules for using DRLs, we are ready to move on to the practice of connecting them. Let's start with the simple and incorrect and end with the complex and correct. Go!

DRL connection diagram without relay

This is the simplest DRL connection diagram, but also the most incorrect. I'll describe it a little. With this connection scheme, you supply voltage to the DRLs from the main power circuit of the car. The main power circuit is activated when the key is turned in the ignition switch. Obviously, your DRLs will always work as long as the key is turned in the ignition, no matter what lighting you use. You have no way to turn off the DRLs until you remove the key from the ignition.

As you already know, the use of DRLs in conjunction with other lighting devices is prohibited. I do not recommend connecting DRLs using this scheme.

Connection diagram for DRL from oil pressure sensor

In this part we will tell you how to connect the DRLs so that they turn on when the engine starts. To connect according to this scheme, you will need a 4-pin relay. The principle of operation of the circuit is approximately the same. In the normal state, relay contacts 30 and 87 are open, i.e. no current passes between them, DRLs are turned off.

As soon as you start the engine, the oil pressure indicator light on the dashboard goes out, a signal from the oil pressure sensor arrives at relay contact 86, this signal excites the coil in the relay, which controls the closure of contacts 30 and 87. After the closure of contacts 30 and 87, your DRLs turn on . This scheme is also not correct because your DRLs will always work as long as your car's engine is running.

DRL connection diagram via 4-pin relay

To connect the DRL according to this scheme, you, as in the previous case, will need a 4-pin relay. Moreover, the connection diagram is absolutely identical to the previous case, only instead of the control signal from the oil pressure sensor, we will use a button in the car interior. Your DRLs will only turn on when you press a button in the cabin.

You can add a little automation to this scheme. In order for the DRLs to go off when the engine is stopped, you can send a signal to the button from the fuel pump, or from the same oil pressure sensor. This scheme already has the right to life, because you can control the DRL operation depending on your driving conditions.

The only downside is that you need to manually turn off the DRLs (press a button in the cabin) when you turn on the low beam headlights, and also manually turn on the DRLs when driving during daylight hours.

Connection diagram for DRL via 5-pin relay

This scheme is the most correct and automated; I recommend connecting the DRLs according to this scheme. This circuit uses a 5-pin relay. Let's talk a little about the operating principle of a 5-pin relay. The 5-pin relay has 2 power outputs. In the normal state, the first of the power terminals is closed, the second is open. After applying a control signal to the relay, the first output will become open and the second will become closed. This seems complicated, but let's look at an example and everything will become clear.

On the image:

Contacts 85 and 86 are control contacts. Depending on whether there is voltage on them or not, contacts 87 or 87A close;
Contact 30 – power supply contact of the relay. It is to this that voltage must be supplied to power consumers;
Contacts 87 and 87A – contacts for connecting consumers.

Let me give you an example. There is no voltage on contacts 85 and 86; power through the relay goes to the consumer at contact 87A. There is voltage on pins 85 and 86, the relay switches power to the consumer on pin 87.

How to connect:

We supply power to the DRLs and headlights through pin 30. For greater automation, take power from the main circuit of the car, which turns on when the ignition is turned on;
We connect DRLs to contact 87A, which will always be on;
We connect the headlights to pin 87, which will turn on only when the DRLs are turned off;
To contacts 85 or 86 (it doesn’t matter), we apply a control signal from the headlights button in the cabin;
We connect the remaining contact 85 or 86 to the car body.

With this connection, either the DRLs or the headlights may work. When the car is turned off, both the DRLs and headlights are turned off.

In my opinion, this is the ideal option.

As is known, the dimensions and power of a switch switching a powerful load must correspond to this load. You cannot turn on such serious current consumers in a car as, say, a radiator fan or glass heating with a tiny button - its contacts will simply burn out after one or two presses. Accordingly, the button should be large, powerful, tight, with a clear fixation of the on/off positions. It must be connected to long thick wires designed to carry the full load current.

But in a modern car with its elegant interior design there is no place for such buttons, and they try to use thick wires with expensive copper sparingly. Therefore, a relay is most often used as a remote power switch - it is installed next to the load or in a relay box, and we control it using a tiny, low-power button with thin wires connected to it, the design of which can easily fit into the interior of a modern car.

Inside the simplest typical relay there is an electromagnet, to which a weak control signal is supplied, and a movable rocker arm, which attracts the triggered electromagnet, in turn closes two power contacts, which turn on a powerful electrical circuit.

In cars, two types of relays are most often used: with a pair of normally open contacts and with three switching contacts. In the latter, when the relay is triggered, one contact closes to the common one, and the second one is disconnected from it at this time. There are, of course, more complex relays, with several groups of contacts in one housing - making, breaking, switching. But they are much less common.

Please note that in the picture below, for a relay with a switching contact triple, the working contacts are numbered. The pair of contacts 1 and 2 are called "normally closed". Pair 2 and 3 are “normally open”. The “normal” state is considered to be the state when voltage is NOT applied to the relay coil.

The most common universal automotive relays and their contact terminals with a standard arrangement of legs for installation in a fuse box or in a remote socket look like this:

The sealed relay from the aftermarket xenon kit looks different. The compound-filled housing allows it to operate reliably when installed near headlights, where water and mud mist penetrate under the hood through the radiator grille. The pinout is non-standard, so the relay is equipped with its own connector.

To switch large currents, tens and hundreds of amperes, relays of a different design than those described above are used. Technically, the essence is unchanged - the winding magnetizes a movable core to itself, which closes the contacts, but the contacts have a significant area, the fastening of the wires is for a bolt from M6 and thicker, the winding is of increased power. Structurally, these relays are similar to the starter solenoid relay. They are used on trucks as ground switches and starting relays for the same starter, on various special equipment to switch on particularly powerful consumers. Occasionally, they are used for emergency switching of Jeeper winches, creating air suspension systems, as the main relay for homemade electric vehicle systems, etc.

By the way, the word “relay” itself is translated from French as “harnessing horses,” and this term appeared in the era of the development of the first telegraph communication lines. The low power of galvanic batteries of that time did not allow transmitting dots and dashes over long distances - all the electricity “went out” on long wires, and the remaining current that reached the correspondent was unable to move the head of the printing machine. As a result, communication lines began to be made “with transfer stations” - at an intermediate point, the weakened current activated not a printing machine, but a weak relay, which, in turn, opened the way for current from a fresh battery - and on and on...

What do you need to know about relay operation?

Operating voltage

The voltage indicated on the relay body is the average optimal voltage. Car relays are printed with “12V”, but they also operate at a voltage of 10 volts, and will also operate at 7-8 volts. Similarly, 14.5-14.8 volts, to which the voltage in the on-board network rises when the engine is running, does not harm them. So 12 volts is a nominal value. Although a relay from a 24-volt truck in a 12-volt network will not work - the difference is too great...

Switching current

The second main parameter of the relay after the operating voltage of the winding is the maximum current that the contact group can pass through without overheating and burning. It is usually indicated on the case - in amperes. In principle, the contacts of all automotive relays are quite powerful; there are no “weaklings” here. Even the smallest switches 15-20 amperes, standard size relays – 20-40 amperes. If the current is indicated double (for example, 30/40 A), then this means short-term and long-term modes. Actually, the current reserve never interferes - but this mainly applies to some kind of non-standard electrical equipment of the car that is connected independently.

Pin numbering

Automotive relay terminals are marked in accordance with the international electrical standard for the automotive industry. The two terminals of the winding are numbered “85” and “86”. The terminals of the contact “two” or “three” (closing or switching) are designated as “30”, “87” and “87a”.

However, the marking, alas, does not provide a guarantee. Russian manufacturers sometimes mark a normally closed contact as “88”, and foreign ones – as “87a”. Unexpected variations of standard numbering are found both among nameless “brands” and among companies like Bosch. And sometimes the contacts are even marked with numbers from 1 to 5. So if the contact type is not marked on the case, which often happens, it is best to check the pinout of the unknown relay using a tester and a 12-volt power source - more on this below.

Terminal material and type

The relay contact terminals to which the electrical wiring is connected can be of a “knife” type (for installing the relay into the connector of the block), as well as a screw terminal (usually for particularly powerful relays or relays of obsolete types). The contacts are either “white” or “yellow”. Yellow and red - brass and copper, matte white - tinned copper or brass, shiny white - nickel-plated steel. Tinned brass and copper do not oxidize, but bare brass and copper are better, although they tend to darken, making contact worse. Nickel-plated steel also does not oxidize, but its resistance is rather high. It’s not bad when the power terminals are copper, and the winding terminals are nickel-plated steel.

Pros and cons of nutrition

In order for the relay to operate, a supply voltage is applied to its winding. Its polarity is indifferent to the relay. Plus on “85” and minus on “86”, or vice versa - it doesn’t matter. One contact of the relay winding, as a rule, is permanently connected to plus or minus, and the second receives control voltage from a button or some electronic module.

In previous years, a permanent connection of the relay to the minus and a positive control signal was more often used; now the reverse option is more common. Although this is not a dogma - it happens in every way, including within the same car. The only exception to the rule is a relay in which a diode is connected parallel to the winding - here polarity is important.

Relay with diode parallel to coil

If the voltage to the relay winding is supplied not by a button, but by an electronic module (standard or non-standard - for example, security equipment), then when turned off the winding gives an inductive voltage surge that can damage the control electronics. To suppress the surge, a protective diode is switched on parallel to the relay winding.

As a rule, these diodes are already present inside electronic components, but sometimes (especially in the case of various additional equipment) a relay with a diode built inside is required (in this case its symbol is marked on the case), and occasionally a remote block with a diode soldered on the wire side is used . And if you are installing some kind of non-standard electrical equipment that, according to the instructions, requires such a relay, you must strictly observe the polarity when connecting the winding.

Case temperature

The relay winding consumes about 2-2.5 watts of power, which is why its body can get quite hot during operation - this is not criminal. But heating is allowed at the winding, and not at the contacts. Overheating of the relay contacts is detrimental: they become charred, destroyed and deformed. This happens most often in unsuccessful examples of relays made in Russia and China, in which the contact planes are sometimes not parallel to each other, the contact surface is insufficient due to misalignment, and point current heating occurs during operation.

The relay does not fail instantly, but sooner or later it stops turning on the load, or vice versa - the contacts are welded to each other, and the relay stops opening. Unfortunately, identifying and preventing such a problem is not entirely realistic.

Relay test

When repairing, a faulty relay is usually temporarily replaced with a working one, and then replaced with a similar one, and that’s the end of it. However, you never know what problems may arise, for example, when installing additional equipment. This means that it will be useful to know the elementary algorithm for checking the relay for the purpose of diagnosing or clarifying the pinout - what if you came across a non-standard one? To do this, we need a power source with a voltage of 12 volts (power supply or two wires from the battery) and a tester turned on in resistance measurement mode.

Let's assume that we have a relay with 4 outputs - that is, with a pair of normally open contacts that work for closure (a relay with a switching contact “three” is checked in a similar way). First, we touch all pairs of contacts one by one with the tester probes. In our case, these are 6 combinations (the image is conditional, purely for understanding).

On one of the combinations of terminals, the ohmmeter should show a resistance of about 80 ohms - this is the winding, remember or mark its contacts (for automobile 12-volt relays of the most common standard sizes, this resistance ranges from 70 to 120 ohms). We apply 12 volts to the winding from the power supply or battery - the relay should clearly click.

Accordingly, the other two terminals should show infinite resistance - these are our normally open working contacts. We connect the tester to them in dialing mode, and simultaneously apply 12 volts to the winding. The relay clicked, the tester beeped - everything is in order, the relay is working.

If suddenly the device shows a short circuit on the working terminals even without applying voltage to the winding, it means that we came across a rare relay with NORMALLY CLOSED contacts (opening when voltage is applied to the winding), or, more likely, the contacts from overload melted and welded, short-circuiting . In the latter case, the relay is sent for scrap.

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