The voltage of charging the car battery from the generator. How to check the generator at home How to check the generator with a multimeter when removing

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Generators are used in many areas as stand-alone sources of electrical energy. These devices are especially widespread in automobiles. Units, devices and units, which are completely dependent on the availability of electricity, will not be able to operate normally without a generator. The battery is also charged from it. Therefore, if any problems arise in the electrical system, one of the main questions becomes how to check the generator with a multimeter.

The best option would be to contact the service station for a complete diagnosis. However, this is not always possible, and the car may not be on the move. The only way out of this situation would be to independently check all vehicle systems, including the generator.

How to check the diode bridge of the generator with a multimeter

The diode bridge in the generator is a kind of rectifier, with the help of which the alternating current generated by the generator is converted into direct current. It includes 6 semiconductor diodes, 3 of them with a positive value, and 3 with a negative value. Each of these groups passes current only in one strictly defined direction.

Alternating current is used when it needs to be transmitted over a long distance. Electrical devices installed in a car require constant current, including for charging the battery. Since the generator is capable of producing only alternating current, a diode bridge is needed to convert to direct current.

The structure includes two metal plates that conduct electric current. Diodes are installed on their plane in order of priority. The alternating voltage produced by the generator changes the direction in which the electrons move. In order to obtain a constant voltage, it is required to redirect their movement in the so-called wrong direction, as a result of the further operation of the phases, a constant current will be created. In this circuit, it serves as a kind of capacitor that successfully dampens voltage fluctuations. If necessary, check the generator with a multimeter.

The diode bridge fails quite often. A similar situation occurs when the polarity of the battery is not observed, or the electrical circuit is closed in the generator itself. Any faults in the diode bridge negatively affect the entire on-board network. If one of the diodes is broken or the diode is broken, in this case dips appear in the stable pulsating voltage at the generator output, since the faulty diode stops supplying voltage to the on-board network.

The battery takes on a certain compensation for the failures at the expense of its own resources, however, the value of the total network voltage is still reduced. In addition to disturbing stability, dips lead to electromagnetic interference, which negatively affects sound-reproducing equipment. With a large number of such violations, it is likely that a mandatory check of the diode bridge will be required. To this end, you will have to check the generator for operability with a multimeter, having previously removed it from the engine. The diode bridge is disconnected and called by the tester.

During disassembly, it is advisable to use the instruction manual, since this operation may differ on different machines. On some models, the bridge is bolted, while on others it is simply soldered. The diode bridge and generator are labeled to avoid confusion during subsequent assembly.

The multimeter must be switched to the resistance measurement mode and the sound indication must be set.
Further, the probes of the measuring device are connected to each terminal of the diode. The negative terminal - "minus" is connected to the central steel or aluminum plate, and the positive terminal is connected to a metal core made in the form of a tinned bare wire, the diameter of which must be at least 1 mm.
To check each diode, you first need to touch the core or center plate with one probe, and the opposite terminal of the diode with the other probe. After that, the probes must be reversed.
If the diode is in good condition, the multimeter will emit sound signals only when the probes are in a certain position. If the tester beeps for all connection options, this indicates that the diode is broken. If there are no sound signals at all, then there is a break in the diode. The audible signals should be emitted by the instrument when only one side of the bridge is being tested.

There is another method for checking the generator with a multimeter. In this case, resistance is used - the main physical quantity. To carry out measurements in this way, the switch must be set to the 1kOhm mark. Touching with probes is carried out as in the previous version. When checking one direction, the device should give a result of 500-800 ohms, and when checking the other - infinity. In this case, all diodes of the bridge are in working order.

How to check the generator voltage regulator with a multimeter

In order to ensure the normal operation of light bulbs, windows, wipers and other electrical equipment, as well as charging the battery, you need to maintain a constant current value at 13.5-14.5 volts. If this indicator is less, then the battery will not be charged, and if it exceeds this level, on-board electrical appliances will fail. High voltages cause some harm to the battery, shortening the life of the battery due to overcharging.

Therefore, to convert the current generated by the generator, there is a special device -. With its help, the on-board network is provided with a current that maintains the required parameters, regardless of the speed of the crankshaft. Situations often arise when it becomes necessary to check the generator voltage with a multimeter.

Modern relays are electronic, and their design is non-separable. If they fail, they cannot be adjusted or repaired, but require a complete replacement. This is considered the only drawback of these devices, since the rest of the relays have a lot of advantages: compactness, durability, high accuracy of current parameters.

The headlights change the brightness of the glow, depending on the engine speed.
There is an insufficient battery charge or, conversely, its overcharging, accompanied by the boiling off of the electrolyte.
A burning odor may be present in the vehicle interior. Damage to the regulator can occur due to moisture ingress, various mechanical damage, short circuit and other non-standard short-term electrical influences.
Sometimes the regulator is initially of poor quality if it is a dubious product from unknown manufacturers.

There are different methods of how to check the generator relay-regulator with a multimeter and establish its operability. The simplest test is considered to be a multimeter, without dismantling the device. For this purpose, the voltage supplied to the battery to charge it is measured. For such a check, you will need an assistant who regulates the engine speed with the accelerator pedal.

The verification procedure takes place in several stages:

The car engine starts and warms up for 5 minutes.
Open the hood while the engine is running and connect the multimeter contacts to the battery terminals. The connection must be made observing the polarity, and the switch is set to the 20 V mark.
The estimation of the charging voltage supplied by the generator is carried out under certain conditions. It is necessary to check how much the generator gives out with a multimeter. The dipped beam should be on, and all other consumers off. The crankshaft rotates at a speed of 1.5 to 2.5 thousand rpm. If the voltage is more than 14.8 volts, then the regulator is considered faulty and must be replaced. Below 13.5 V, the relay is not the only cause of failure. The fault could be in the wiring or the generator itself.
More accurate results are obtained by evaluating the intensity of the current supplied by the load. This will require the inclusion of a high beam, stove fan, wiper and other consumers. In such a situation, the value of the charging current should not be lower than the 13.5 volt mark. If the indicator is still less than this value, then when all electrical equipment is turned on, the battery will not receive normal charging.

A more complete check is performed on the removed relay-regulator. Usually the electronic device sits on top of the generator, covered with a plastic cover. In some cases, the regulator can form a single unit with brushes. To check, in addition to a multimeter, you need to prepare a test lamp for 12 V, with a power not exceeding 3 watts and an adjustable current source. These methods are also suitable for checking the generator integral with a multimeter, that is, an integral voltage regulator.

The wires from the power source are connected as follows: "minus" is connected to the regulator ground, and "plus" is connected to the terminal marked with the symbol "B". The test lamp is connected through conductors with graphite brushes without observing polarity. First, a voltage of 13 to 13.5V must be applied to the relay-regulator, at which the light will be on. If this does not happen, then the control device is faulty.

Further, the light bulb remains lit, and the incoming voltage gradually increases. With a working relay, the light will go out when the voltage reaches 14.2-14.5 V. If, in the event of a further increase in voltage, the control light continues to light, then there is a breakdown in the relay and it is faulty. A malfunction is also evidenced by the fact when the light goes out at a voltage below 4 V. Such a current will be clearly insufficient to provide power to all electrical appliances and to charge the battery with high quality.

How to check the generator rotor with a multimeter

A defective rotor in a car alternator primarily causes the charging current to disappear and the battery to discharge. This is indicated by the battery discharge lamp located on the instrument panel. The position of the voltmeter needle is near the red zone or in the zone itself. In this regard, it becomes necessary to check the generator armature with a multimeter.

When checking the voltage with a multimeter with the engine running, its readings on the battery terminals will be less than the required 13.6 volts. In order to obtain more accurate results, it is recommended to check the charging of the battery from the generator with a multimeter in advance.

The main faults of the rotor are considered to be a short circuit of the windings and a rupture of the terminals between the field winding and the slip rings. To check, it is not necessary to remove the generator from the engine and remove the rotor from it. It is enough to remove the voltage regulator relay and perform all the necessary actions through the resulting window.

In order to check the presence of a short to ground in the rotor field windings, you need to set the multimeter to the mode and press the positive probe alternately to the slip rings. The negative probe is pressed against the mass - the generator body. If the resistance indicator tends to infinity, then the rotor is operational and there is no short circuit to ground. After that, you should check the generator winding with a multimeter for an open circuit. The multimeter is also set to ohmmeter mode, the positive probe is applied to one slip ring, and the negative probe to the other. A resistance indicator from 5 to 10 ohms indicates the serviceability of the excitation winding. In most cases, a defective rotor must be replaced.

However, not all items can be verified through testing. For example, it is not possible to check the generator brushes with a multimeter. This procedure involves visual diagnostics after the brush set has been removed. The voltage regulator can also be removed if necessary. As a rule, the brushes show even wear. In the normal state, the length of the brushes is 8-10 mm. If this indicator is less than 4.5 mm, then the brushes must be replaced. At the same time, coal dust, formed as a result of the friction of the brushes on the rotor rings, is cleaned out.

When performing generator diagnostics, rotor malfunction is allowed last. First of all, other elements are checked that are more likely to cause malfunctions of the device. Low voltage, a lit lamp on the instrument panel and other symptoms can occur in the event of a failure of the diode bridge or relay-regulator. They are checked first, and only then the rotor itself.

Car battery and alternator check

The car has two power sources - a battery and a generator. The first supplies the electrical circuit when the engine is not running. The second is when the engine is already running. In this case, the battery switches to the mode of an electric current consumer and replenishes the consumed energy to start the engine.

In practice, malfunctions of one or another power source are quite common. They often appear in the same way. The starter refuses to spin the engine, and as a result, the engine does not start. When the engine is running, the control lamp on the instrument panel with the battery icon comes on. It indicates that a malfunction has occurred and the battery is not charging.

Checking the generator on the machine

First of all, you need to see if the alternator belt is intact. If it is not torn, then the belt tension is checked. Then the turn for the battery. We measure the voltage at the terminals with a tester (multimeter). It should be around 12-12.7 volts. If everything is ok, start the engine. If the battery is discharged, charge and start the engine again.

We measure the voltage at the terminals of the storage battery (accumulator battery). It should be within the specified range, usually 13.2 to 14.5 volts. But on modern cars, these limits may differ. If an operating manual is available, you can refer to it. Any deviation from the specified values is a malfunction. These deviations can be of three types:

Lack of charging current- the generator does not work.
The charging current is present, but below the minimum value- there is insufficient battery charge.
Voltage above maximum value- recharge the battery.

All three cases indicate an existing malfunction in the vehicle's electrical supply system. you need to carry out a comprehensive check of the generator.

But before that, conduct a visual inspection of all wires and cables that go from the generator to the battery. There should be no visible damage, breakage and oxidation of the electrical wiring. Be sure to check the terminals on the battery, starter and alternator. They must be clean and dry. Any oxidation, rust and dirt must be cleaned. Often this helps to restore the lost contact and the car starts to work as expected. If this does not help, we proceed to a detailed check.

It is best to remove the alternator from the vehicle for further checking. First of all, remove the relay-regulator from the generator and check it. To check the voltage regulator, you will need a multimeter and a voltage regulator charger. It would be better to use a power supply instead of a charger. Adjusting the voltage from 0 to 16 volts will be sufficient.

Connect the plus of the power supply to the regulator - usually this is a male plug connection. Catch minus to minus, it is usually displayed on the ear of the relay mounting. Connect the red wire of the tester to the positive wire of the power supply, the black wire to the negative. Connect two stripped wires to the brushes, one for each. A light bulb is connected to the other pre-stripped ends (it can be removed from the rear lights of the car for the duration of the check). The test stand is ready.

Ringing relay-regulator

Connect the power supply to the mains, carefully use the regulator knob to start raising the voltage. At the same time, observe the readings of the multimeter. The light at the very beginning should not be lit, but as the voltage rises, it should light up, first at half-incandescence, and as the voltage is added, the brightness should increase.

When the 14.5 volt mark is reached, the regulator should work, cutting off the voltage. The light should then go out. It is generally accepted that the stabilizer is working if it cuts off the current at values from 14.2 to 14.8 volts. If this happens at lower or higher rates, then the voltage regulator is faulty. And also the relay is faulty if there is no current cutoff at all.

In the event of a failure, the relay is replaced with a new one. If it works, we continue checking.

How to check the generator with a multimeter

The diode bridge of the generator can be checked with a multimeter, but you can also use a stand that checked the regulator.

But before that, first of all, without removing the rectifier bridge from the generator, connect the red wire of the tester to terminal 30 of the generator, and the black wire to the body. Set the tester operating mode to dial tone (diode icon). If it is not, then put on 1-2 kOhm. The multimeter should show infinity. If the readings are different, the diode bridge is faulty.

Then check the rectifiers for breakdown. Leave the positive (red) probe at terminal 30, with the negative touch the axle bolts in turn. The multimeter display in all cases should give infinity, any other means a breakdown.

But in practice, such a check is often not enough. In most cases, it is necessary to ring the generator in more detail.

Careful dialing

To do this, unscrew the fixing bolts of the rectifier unit, disconnect the copper wires of the stator winding and remove the diode bridge from the generator. Now you can check each semiconductor individually. Before checking, it is advisable to rinse the stabilizer with running water using a medium-hard brush, and then dry thoroughly. A hair dryer is fine for quick drying.

Attach one of the tester probes to the diode plate, connect the other to the central terminal of each diode fixed on this plate. Then swap the test leads. In one case, the multimeter should show infinity, in the other - a nominal resistance equal to approximately 570-590 ohms. Rectifiers are considered defective if:

In the first and second measurements (when the polarity was changed), the readings of the multimeter are the same;
The resistance of the diodes is greater or less than the nominal values.

Do the same for the second plate of the diode bridge. If a malfunction is detected one or more diodes, it will be easier to replace the entire rectifier unit. True, there are craftsmen who change the failed diodes separately, but such work requires a certain skill and dexterity.

Checking the armature and stator windings

Further checking requires a complete disassembly of the generator. First of all, visually check the anchor. The brush rings must be free from blackening, chipping and wear on the treadmills. Blackening and slight wear can be removed with zero emery cloth. Rings with deep grooves must be replaced or - if the thickness of the rings permits - turned on a lathe.

The armature winding should not clearly smell like fumes.... The color of the winding should be uniform, not damaged or broken. To check the armature winding for an open, you need a multimeter. Set the operating mode for continuity or resistance measurement and connect the probes to the brush rings. The winding resistance should be between 3-5 ohms. Then leave one probe on the ring, connect the other to the body. The multimeter display should show infinity.

The generator stator is diagnosed after being removed from the housing. Perform a visual inspection first. There should be no visible damage to the wire and its insulation. Then connect the tester wire to the stator housing. With the second wire, touch the leads in turn. There are only three of them. The tester must be in dial mode. If the display shows infinity, then this indicates the health of the stator.

A further check consists in diagnostics of the windings. The resistance of all three windings must be the same.

Before assembling the generator, the bearings must be checked and, if necessary, replaced. When turning, they should not wedge or make a creaking sound. This suggests that they are badly worn out and they will soon fail. Therefore, it is better to replace them immediately..

The task of the generator, as the main source of electricity in the car, is to generate and maintain voltage at a certain level, regardless of the level of load on the on-board network.

A fully functional unit should produce 13-14.5 volts.

Voltage stability is maintained by an electronic relay-regulator, which in most cases is built directly into the generator. Its failure sharply limits the possibilities of operating the machine: in this case, the only source of energy will be the battery, which will soon be discharged. What breakdowns happen with this device, how to check the generator and what is the cause of breakdowns, this is described below.

Symptoms of a generator malfunction

Full or partial failure of the device can be determined by the following criteria:

The warning light on the instrument panel, usually in the form of an image of the battery, flashes or stays on. This indicates that the battery is not charging or the current supplied to it is insufficient.
Permanent failures in electrical equipment: unstable operation of external and internal lighting, when the lamps burn either brighter or dimmer, heating with the engine running (if the engine is turned off, then everything functions normally). By the way, lighting problems can be observed if necessary.
The battery is constantly and frequently discharged.
A burning smell is felt in the passenger compartment or engine compartment.
Whistling or excessively loud rustling is heard from the generator side.
The generator hums strongly during operation: the diode bridge or stator windings are faulty.

The appearance of the above signs indicates the need for an immediate diagnosis. But how do you test the generator yourself? If you know how to handle a multimeter, then diagnostics can be carried out without contacting a car service. However, you first need to decide on the nature of the breakdown. Damage can be both electrical and mechanical.

Generator malfunctions and reasons for its failure

First, a little about the design of the device. The main components of the generator are the stator (stationary element), the rotor (rotating part), brushes, a built-in relay-regulator unit, a diode bridge and a housing with bearings.

And now - about the most typical malfunctions:

Seized bearings. This problem most often occurs with a generator that has been in operation for a long time. Dirt, dust, moisture are gradually doing their job: as a result, the bearings jam, the rotor of the device stops spinning and the drive belt breaks. There is a nuance here: sometimes the generator does not completely stop - it "wedges up". In this case, a characteristic whistle will be heard, indicating increased friction in the collapsing bearings. When replacing these elements, it is recommended to install two new ones at once (in the rear and front cover of the generator).
Combustion, turn-to-turn closure of the rotor or stator winding. The reasons for this malfunction are also not original: it is moisture and salt on the roads, which in a "pair" corrode the varnish insulation of the windings, as a result of which a short circuit occurs and eventually burns out the wires.
Broken or worn brushes. By design, they are graphite square or rectangular products in contact with the copper tracks (slip rings) of the stator. Most often, brushes wear out, less often they break. Sometimes their performance can be determined visually: put the car in a dark garage and start the engine, after opening the hood. Sparking inside the generator indicates worn brushes.
Malfunctioning voltage regulator. This is an electronic unit, the task of which is to maintain the voltage at the same level, ensure the supply of the rated current to the battery and prevent it from overcharging (which leads to the evaporation of the electrolyte).
Rectifier unit malfunctions. It consists of several electronic components forming a diode bridge. If at least one of them fails, the current stops rectifying, the functioning of the voltage regulator stops: the on-board network starts to be powered only from the battery, the service life of which is limited.

How to check battery charging and generator performance with a multimeter

To carry out this procedure, it is not at all necessary to have a professional tester: an ordinary multimeter is suitable, in which there are modes for measuring resistance (ohmmeter) and voltage. First you need to take measurements with the engine off. Attach the test leads of the multimeter to the battery terminals: the tester should show at least 12.5 volts (with a normally charged battery).

Now start the car and, without turning on any consumer, measure the voltage again: it should be in the range of 13.8-14.5 V. At the next stage, you will need to connect the load to the on-board network: heater at full power, multimedia, headlights (high beam ), foglights and heated rear window. Look at the device: with a working generator, the voltage will drop to 13.7-14 V. If the value is lower, you will have to test the generator. The following describes how to check the generator and its components without removing the device from the car.

Voltage regulator

The purpose of this block (some call it a "chocolate" or "pill") built into the generator is to stabilize the on-board voltage. To check the generator with a multimeter along with the regulator, the latter does not need to be removed from the machine. You will need to carry out the operation described above: that is, measure the battery voltage with the engine off and running. A downward deviation from the norm indicates a malfunction of either the voltage regulator or the generator. But exceeding the parameter of 14.5 volts indicates a failure of the relay, which is fraught with constant boiling of the battery. To more accurately check the voltage regulator, it must be removed. It is not difficult and dismantling can be done directly on the installed generator: just unscrew 2-3 screws (the number depends on the car model). Next steps:

disconnect the positive terminal from the battery;
take the regulator and connect the "+" of the battery to its terminal (where the thin wire from the generator is connected), connect the minus to the second contact of the relay ("ground");
connect any 12 V car lamp to the brushes of the voltage regulator;
its glow will indicate the health of the unit.

Checking the diode bridge without removing it from the car

The function of this block is to rectify AC to convert to DC. The bridge most often includes 6 semiconductor diodes. Three of them conduct current only in one direction, three in the other. To check the generator with a multimeter and at the same time the integrity of the diodes, you will need to remove the wires connected to the voltage regulator, generator. Remember to disconnect the "-" from the battery. Switch the tester to the resistance range. Connect the positive probe (it has a red tint) of the device to the generator terminal "30" (the thickest cable stretched from the battery is suitable here), the negative (black) probe to the body ("mass") of the device.

If the diode bridge is working properly, then the tester readings are infinitely large resistance. If it is some ohm, then the rectifier needs to be changed.

Checking diodes with a multimeter on a dismantled and disassembled generator

The bridge includes a pair of aluminum plates: one of them is "minus", the second is "plus". Take the tester and put one of its probes to the plate, and with the second touch, in turn, the contacts of the diodes fixed on the plate. The device should show infinity or resistance (usually several kilo-ohms). Then change the probes: the opposite picture should be obtained. We do the same with the second plate. If the readings on some diode are equal to zero, then it is broken and must be replaced. If all the diodes show a certain resistance, and one of them - infinity, then this means an open circuit: the electronic component also needs to be replaced.

Checking the rotor windings

When the generator brushes are not worn out and their length is 4.5 mm or more, and the diode bridge is intact, you can start checking the rotor. To do this, the generator will have to be removed and disassembled. The dismantled device must be divided into two parts by unscrewing the fastening bolts. On one of them you will see a shaft on which copper slip rings are fixed. How to check the generator in this case? You just need to set the measuring device in ohmmeter mode with a measurement range of 50-100 ohms and attach each probe of the device to the slip rings. The arrow (or numbers appear) of the multimeter will deviate to 2-5 ohms. If it is higher, then this is a sign of unreliable contact between the rings (poor soldering of the winding leads is possible). With a lower resistance, the turn-to-turn closure of the windings is obvious.

To be sure of the condition of the rotor, it is worth doing one more check. The voltage of 12 volts from the battery should be applied to the slip rings, connect the tester to the break of the negative or positive wire, setting it to the current measurement mode (observe the polarity of connecting the instrument probes). Its value should be in the range of 3-4.5 A. A higher current strength indicates an inter-turn closure of the windings. It is possible to determine their inoperability purely visually: the dark color of the wires and the smell of burning will tell you about this.

Insulation resistance test

You will need 220 volts and a lamp designed for this voltage. Connect one wire to any slip ring, the other to the rotor housing. With an intact and open winding, the light will not light. If it is burning or even slightly glowing, the winding will have to be repaired (rewound in a profile workshop) or changed.

Checking the stator windings

This procedure also requires the dismantling of the generator followed by its disassembly. This part of the device has several windings, so you will have to check each one. First, disconnect the wires leading from the diode bridge to the windings (you may need a soldering iron). Later:

Switch the measuring device to ohmmeter mode, to the minimum limit - usually 1 (which is better) or 10 ohms. All measurements are recommended to be carried out with a more accurate digital device.
Connect the tester probes alternately to the winding leads. The device should "give out" almost 0.2 Ohm.
Test the resistance between one of the terminals of the coil and the "zero" (common wire) of the stator. The normal reading of the tester is 0.3 Ohm.
Also check the integrity of the insulation. Connect one wire connected to a 220 V household outlet to the rotor body, the second through a conventional 25-40 W filament lamp connected in series to the winding terminal. If the latter is not defective (insulation is not broken), the lamp will not light up.

At the same time, carefully inspect the "insides" of the stator and the rotor: no traces of contact are allowed here. If they are present, this indicates wear of the bearings or bushings, which confirms the "abnormal" noise emitted by the generator when the engine is running. By the way, if - this may be a sign of several malfunctions at once.

Checking generator brushes and slip rings

Their performance is determined visually. The minimum length of these products is 4.5 mm (new ones are 8-10 mm). The main reason for the failure of brushes is their long-term operation. Sometimes they wear out quickly and even break due to the skew of the rotor shaft, which is associated with a factory defect or deformation of the device due to, for example, an accident. The brush assembly is most often structurally combined with a voltage relay, so this unit can be removed without dismantling the generator. But you will have to buy the entire unit assembly: a relay-regulator and a brush holder.

The diameter of the new slip rings is 14.2-14.4 mm. A minimum value of 12.8 mm is allowed. These products can be purchased freely at a car dealership.

To replace, unsolder the contact wires from the winding and dismantle the rings with a puller. New ones, before installation, can be processed with emery cloth on a lathe: this will eliminate the beats associated with surface irregularities and eliminate burrs.

Alternator bearing wear

To replace them, the generator must be removed from the machine and disassembled as described below:

remove the back cover (usually made of plastic) by unscrewing the clips or unscrewing the screws;
disconnect the brush assembly combined with the relay-regulator;
dismantle the diode bridge by unscrewing 3 screws;
dismantle the metal back cover located under the plastic one and pull out the stator;
pull out the rotor and clamp it in a vice to remove the pulley, after unscrewing the nut that secures it to the shaft;
remove the front cover together with the bearing: according to the manufacturer, it must be replaced as a complete unit.

If you decide to replace the bearing separately, take an electric drill with a drill with a diameter of 4 mm and drill the cover in the punching places. Knock out the old bearing, insert the new one and close it. The rear bearing is easier to remove: just use a puller with two lugs. In some car models, the generator is non-separable: the stator winding is soldered to the cover. Then you have to unsolder the wires to remove the stator. When choosing a bearing, it is worth paying attention to - their cost, as a rule, is lower, and the quality may not be inferior to the original.

It often happens that the generator stops functioning only on a warm engine. A similar phenomenon is due to the natural expansion of the metal with an increase in temperature or a change in the properties of semiconductors (diodes) for the same reason. In this case, checking the generator's performance should first be carried out on a warmed-up car, and if this does not bring results, then dismantle and check the device, having previously heated it with a construction hairdryer. In conclusion, it is worth noting that independent replacement of such generator components as stator or rotor windings, bearings in domestic conditions is advisable only if you have the appropriate equipment, tools, and experience. If it is not there, then in the absence of battery charging, limit yourself to an attempt to replace the relay-regulator combined with the brush assembly. For this, it is not necessary to buy a new device: you can put a known good one and evaluate the result.

The generator is the main power source for the vehicle electrical system. A car generator is obliged to provide a strictly normalized voltage value, regardless of the amount of load on the on-board network (meaning the standard load, without powerful external consumers). The overwhelming majority of the generator voltage during operation in a car should be 13 ... 14.5 V. Its design has been developed a long time ago and has not radically changed since then, therefore, a unified diagnostic technique allows you to identify malfunctions of any generators.

The appearance of the car generator

Some of the finer points of home validation may vary from model to model, but the basics are the same everywhere.

Vehicle generator device

Any generator consists of the following parts:

Automotive generator device

The stationary part of the generator, the stator, has a polyphase winding (4) and serves as a voltage source in the car. As a rule, it has three windings, connected in a star. A rotor (2) rotates inside the stator, on which the field winding is wound. By changing the voltage on this winding, you can adjust the output voltage of the generator. This is done by a special device, the relay is a regulator.

Most modern generators have a built-in voltage regulator (5), which is attached to the stator and has terminals for connecting voltage and graphite brushes for contact with the slip rings of the field winding. Bearings (1) and (3) are designed to ensure ease of rotation and centering of the rotor within the stator. The stator windings generate alternating voltage during operation, therefore the car generator is equipped with rectifier diodes, which are made on a separate panel and are attached to the stator housing. Since there are three windings, six diodes are used for rectification (three-phase bridge rectification circuit).

A pulley is attached to the shaft of a car generator to transmit torque from the engine. The stator together with the side covers form a single structure and is fixed to the motor housing with the possibility of adjusting the position.

Major malfunctions

The main faults are listed below in order of frequency:

loosening the tension of the alternator belt;
failure of the voltage regulator;
wear or sticking of brushes;
breakage or short circuit of windings;
breakdown of rectifier diodes.

The need to diagnose the generator arises if the voltage of the on-board network in the car does not match the required value, or if it is completely absent. It often happens that at low load the voltage is normal, and with an increase in the consumed current, the voltage drops. Before checking the car generator, you first need to check the tension of the generator belt. To check, it is enough to press down on the belt with your finger and measure the amount of deflection. It should be no more than 10 ... 15 mm.

Greater deflection will lead to the fact that when the load on the generator increases, the friction force between the belt and the pulley will not be sufficient to fully transfer the torque from the engine, and the belt will slip. The adjusting screw must be used to move the generator stator away from the engine. If the belt tension is normal, then the car generator requires a deeper check.

An increase in voltage while the engine is running may indicate a voltage regulator malfunction.

Car generator check

To check the generator in a car at home, you need a measuring device - a tester, which has functions for measuring voltage and resistance. Now the most widespread and low cost digital testers (fig. Below).

Digital tester for measuring electrical equipment

Such a device is sufficient for carrying out almost any measurements in the electrical equipment of a car. In addition, the operability of the devices is carried out without observing the polarity of the connection of the probes.

Some measurements are taken with the engine running.

In this case, the operation of the generator is checked only with a connected battery. Without a battery, the voltage regulator will not function normally, and an overestimated voltage will enter the car's on-board network, which will most likely lead to the failure of the on-board controller and other electronics.

Below we will tell you how to check the generator with a multimeter. First of all, you need to measure the voltage at the battery terminals with a tester when the engine is not running. After the engine is started, the voltage should rise and reach the nominal value, which means the battery is charging. Otherwise, the generator must be dismantled and fully checked. You can check a car generator without removing it from the car, but this technique differs significantly depending on the brand of car and generator.

Checking the dismantled generator includes:

visual inspection for abrasion of insulation, burning of wires, condition of brushes;
checking the resistance of the stator and rotor windings;
performance of rectifier diodes;
operability of the voltage regulator (relay - regulator).

When examining the removed generator, first of all, it is necessary to make sure that there are no mechanical damage to the windings, the reliability of the terminal connections, the integrity of the diode terminals. The brushes of the relay-regulator should move freely in their guides and not be chipped.

The slip rings of the field winding on the rotor shaft must not have burrs and traces of burning. Heavy carbon deposits and traces of burnt metal on the rings indicate a short circuit between the turns of the rotor winding.

The stator and rotor windings are checked with an ohmmeter. The resistance of the windings should be several ohms. The field winding is checked by measuring the resistance between slip rings on the rotor shaft. Normal resistance should be 5 ... 10 ohms. The stator winding is checked only after disconnecting all terminals. The winding should have three free wires (on new generators) or four (output from the connection point of the windings on old generators). Automotive stator must have winding resistance within 5-15 ohms between the beginning of the winding and the connection point and 10..30 ohms between the ends of adjacent windings. The main thing here is that the stator has the same value when measuring all three windings. A difference of more than 20% indicates a malfunction of one of the windings.

When measuring small values of resistance, the probes of the device introduce an error. For accuracy, you must first connect the probes to each other and determine their resistance. Usually it is 0.2 ... 1 ohm. This value should be taken into account in further measurements.

Next, you should check the condition of the diodes of the rectifier bridge. Most generators in a car use two types of diodes. Some of them have a negative terminal on the body and a positive free one. Others are done the other way around. This is done for the convenience of mounting diodes on cooling plates - heatsinks (Fig. Below).

Car generator diode bridge

It doesn't matter for measurements. Diodes are measured when the ohmmeter switch is positioned to measure diodes. If there is no such position or a dial gauge is used, then the measurement limit is set for resistance measurements of 200 ... 1000 kOhm.

The rectifier bridge must be disconnected from the stator. The operation of the diodes is checked by comparing the resistances with the forward and reverse polarity of the device probes. The values must differ several times. The ideal case is when in one polarity the device shows a complete break and the measured values are the same for all diodes. If in both positions of the probes the device shows zero resistance or its complete absence, then such a car diode bridge requires replacement.

In addition to checking the resistance, it is also necessary to check the condition of the insulation of the windings. For this, the measurement limit of the device is set to measure the maximum resistance, then one of the probes is applied to the generator case (on the stator), and the other probe is applied to the tested winding. The readings of the device should show a very high resistance (on the arrow, the arrows should not deviate).

More precisely, the insulation resistance can be checked using a special instrument (megohmmeter) used to measure electrical cables or cable communication lines.

Two wires are taken out of the lamp holder, one of which is connected to the generator case, since the stator has a metal case, and the second is connected to a regular household outlet. The second terminal of the socket is connected to the tested winding. The absence of light from the lamp indicates the normal state of the insulation.

Checking the voltage regulator

You can check the voltage regulator (relay-regulator) using an external regulated power supply 12… 16 V (Fig. Below).

Relay-regulator test circuit

To check, an adjustable source is connected to the relay with a plus to the output terminal, and a minus to ground. A 12 V car lamp is connected to the brushes. When the power supply voltage is more than 14.5 V, the lamp should go out. A defective voltage regulator needs to be replaced. Relay - old type regulator to be adjusted.

Video. Quick check

Quite often, malfunctions occur in a car with a warm engine. This can be associated with both the linear expansion of the metal from temperature (short-circuiting of the windings), and with the properties of semiconductors (rectifier diode malfunction). In this case, we recommend checking the generator's operation directly on the car. The question of how to check the generator after heating is solved by warming up with a construction hairdryer to the possible operating temperature.

Repairing a car generator at home requires a lot of qualifications and, in most cases, is impractical. It is much easier to replace it completely. An exception is the automotive relay-regulator and the diode bridge.

Every car enthusiast is faced with generator maintenance. There are cases of its failure and it is not always correct to give it to a service center or buy a new one. You can restore its performance yourself and it can be done quite simply. In this case, you need to know the principle of operation, thanks to which it is very easy to check the generator for serviceability.

basic information

Generators are used to generate electrical energy. They transform other energy, with the help of which an electric current is obtained, which appears in the conductor due to the electromotive force (EMF). This force makes charged particles, called electrons, move in a directed manner. The electron has a negative charge. When a conductor is placed in an electromagnetic field and it makes movements, a potential difference is formed.

This condition can also be viewed from the reverse side: under the action of a moving one uniformly or uniformly accelerated, a current begins to be generated in the conductor. This phenomenon is called electromagnetic induction, which is widely used in the manufacture of various types of devices and electrical machines. Transformers, electric motors and current generators are made on this principle.

A current generator is a type of electrical machine that converts various types of energy into electrical energy. In order to check the operation of the generator on a car, you need to familiarize yourself with its structure and principle of operation.

Electric generator device

Generators of any type are the same in design, but there are some differences. The device consists of the following main parts:

The body is the main part of any generator, since it carries out the fastening of the main components and mechanisms. In it, bearings are installed, which extend the service life of the electric generator (hereinafter referred to as EG) and soften the shocks during the rotation of the rotor. The body of the device is made of durable alloy. In addition, it serves to protect against mechanical damage, dust, moisture and the negative influence of external factors.

The stator, which has magnetic poles, is made of a special electrical winding. Magnetic poles are windings consisting of a certain number of turns of wire, the diameter of which is selected by calculation.

The rotor is set in motion by an external force; during its rotation, a potential difference is formed. The voltage (U) or potential difference is fed through the rings to the connection box. From the box it is diverted for further conversion into a higher quality voltage.

Principle of operation

The principle of operation is based on the law of electromagnetic induction. When rotating in a uniform magnetic field, U is formed on the rotor. The work of the EG consists of the following points:

The rings, made of a copper conductor, rotate synchronously with the rotor, and are needed for the flow of current to the rings. All EGs differ in design, method of excitation of the stator windings, the number of phases and the type of connection of the windings. Based on the constructive plan, two types are distinguished:

Fixed poles at which the armature rotates.
Movable poles.

The latter type is widely used, since it generates a relatively large current with smaller dimensions and obtains U, which is close to sinusoidal. This type has 3 main modifications:

Independent arousal.
Self-excitation.
Work from permanent magnets.

The first model is powered by an external source of mechanical, thermal, water and other types of energy. The second model is powered by its own rectified current, and the work of the latter is carried out using permanent magnets that form a magnetic field with a constant component F.

One of the most popular is the star connection (scheme 1) with a neutral wire, which is a phase imbalance compensator. In addition, the neutral wire excludes a decrease in power and heating of the stator coils when exposed to a ring current (I).

Scheme 1 - Star connection.

To the star-connected windings, the load of the active component with the neutral wire is minimal. However, there is another scheme (scheme 2) for connecting the stator coils of the EG with a triangle. It is rarely used in a domestic environment.

Scheme 2 - Delta connection of stator windings.

With this type of winding connection, devices and mechanisms of relatively low power should be connected. All types of generators have different technical characteristics (TX).

Specifications

EGs differ among themselves in the main technical parameters: generated U, I and power (P), as well as rotor speed and coefficient of P (cosph).

Regulation of U is carried out due to a change in F. For this, special devices - regulators U are connected in series to the circuit of the excitation windings. If a third-party motor is used to rotate the EG shaft, then the revolutions are regulated on it. When using generators, the excitation of which occurs from permanent magnets, it is necessary to use a regulator and stabilizer U.

For the network connection, a parallel connection of power generators is used. It is necessary to monitor the equality of the EMF, the phase shift is equal to 0. This process is called the synchronization of the EG with the supply network and for this a special device is used, which is called a synchroscope. A synchroscope is an ordinary lamp with a voltmeter. It is connected in series to the EG. During the start-up of the electric generator, the excitation I on the stator coils is adjusted.

The lamp starts blinking, and when approaching the optimal value of the current, these blinks become more intense. Eventually it goes out, in which case the synchronization process is complete. In addition, the readings of the voltmeter, which is also called zero, should be equal to 0.

Applications

Three-phase generators are used together with a diode bridge for powering the on-board network, ignition system, light signaling and lighting, on-board computer and other car equipment. The connection is made to the U regulator on an integral (integrated microcircuit), which stabilizes its values within the normal range.

Generators differ in their areas of application and their main types should be distinguished: automobile, electric, inverter, diesel, synchronous, asynchronous, electrochemical.

The battery for the car is used for short-term rotation of the crankshaft using a starter. The starter is powered by a battery, which is a hybrid in most modern cars. When exposed to the excitation winding when the ignition is turned on, I flows through the rings and generates an electromagnetic field in the excitation winding, due to which the rotor is started. The rotor creates electromagnetic waves that penetrate the stator windings.

An electric generator is necessary to convert energy from various third-party sources that affect the shaft of the latter. In addition, inverter types of EG are now common. They produce high-quality electricity and are an autonomous power source. The basic principle of operation of such an inverter generator is as follows:

High-quality alternating current is generated and rectified by means of a diode bridge, at the output of which a constant U appears.
Constant U is accumulated in storage batteries, from which, with the help of an inverter, is converted into alternating current.

A diesel generator is often used for domestic needs. It converts energy from the combustion of fuel into electrical energy. Fuel is a chemical form of energy, and combustion is oxidized by oxygen in the air. During combustion, thermal energy is transformed into mechanical energy, and then, according to the principle of operation of the generator, an electric current is obtained.

The rotor of the synchronous EG is a permanent magnet. This magnet has poles, the number of which can range from 2 or more, but this value is always a multiple of two. When the EG is started, the rotor produces an electromagnetic field and with an increase in the rotation frequency, I appears in the windings. As a result, U appears, which is controlled by a special device. In this case, the voltage is stable, and therefore, this fact is a positive side of this type of EG.

In some cases, a significant overload according to I is possible. This type requires the use of additional equipment for overload protection. Electric generators of asynchronous type differ from synchronous ones in that the rotor rotates with some advance.

A chemical energy source or electrochemical generator is a very interesting and environmentally friendly invention. Its principle of operation is the interaction of hydrogen and oxygen. The use of these elements makes it dangerous: hydrogen is an explosive gas, and oxygen is a powerful oxidizing agent (when hydrogen ignites, the fire will only intensify due to the oxygen catalyst). It should be noted that when using any generator, except for the inverter one, additional protection devices and regulation of the parameters of the output U and I should be used.

Methods for checking on cars

Sometimes the generator breaks down on a car, motorcycle and other forms of transport. There are such options for solving the problem: repair in a service center, buying a new one or repairing on your own. In addition, immediately upon purchase, you need to check the charging of the battery generator. If the battery is new, then in case of unsuccessful attempts to charge it, the latter may fail. The first two options require an investment of money, although many motorists prefer to solve the problem on their own. To eliminate basic malfunctions, you need to know the typical breakdowns:

Seized bearings.
Burnout of the windings.
Faulty brushes.
Failure of the relay used in the U controller.

When the bearings are jammed, the rotor is jammed and to eliminate this problem, the bearings must be disassembled and lubricated. In addition, if they have become unusable, then you need to replace them with others.

When the windings of the rotor and stator coils burn out, it must be ringed with a tester for short-circuited turns, and, if necessary, rewound. As a rule, the brushes need to be replaced, but there are cases of loosening of the springs necessary to damp the rotation of the shaft and brush assembly. In this case, the springs must also be replaced. The regulator relay U is responsible for charging the battery from the EG and if it fails, the battery is not charged at all.

Basically, electrical malfunctions occur and it is quite simple to check the generator on the machine without removing it. There are 2 ways to check: ring the generator with a multimeter and check the operation of the generator on the car under load.

Checking a car generator at home using a multimeter can be roughly divided into several stages:

To check, you need to know exactly the model and parameters of the EG: U, I, winding resistance (R). It (EG) needs to be disconnected from the car wiring and start, and then compare the indicators with the required ones.

The second method is simple and gives the same result as the first. The main steps for checking a generator for a VAZ (although this method can be used to check the EG for any type of transport):

Thus, there is no need to go to a service center to repair a car EG or buy a new one. First of all, you need to deal with the malfunction, because in most cases it turns out to be quite primitive and can be easily eliminated even by an inexperienced motorist.