How to check the generator for performance in various ways. How to check a car generator with a multimeter How to check if a generator is producing current

10.01.2022

The main source of power in the car is the generator, it is such a "mini-power plant". Incorrect or unstable operation of this node is fraught with bad (battery). A failed generator does not provide charging, therefore, the on-board network of the car will work on a battery that will not last for a long time. As a result, the battery is completely discharged, the engine "stalls" somewhere outside the city, and you have a new "headache" and the need to replace the generator.

In order to prevent such a scenario, it is necessary to regularly monitor the status of this device, as well as the charging it gives. If you notice any interruptions in work, you need to check the generator, and you will now learn how to do this.

But before that, I consider it necessary to talk about precautions and certain rules that must be observed when checking this electrical appliance in order not to damage it.

!!! It is forbidden:

Check the performance of the generator by short circuit, that is, "to a spark."
Connect terminal 30 (in some cases B+) to ground or terminal 67 (in some cases D+).
Allow the generator to work without consumers turned on, it is especially undesirable to work with the battery disconnected.
Carry out welding work on the car body with the wires of the generator and battery connected.

!!! Important:
Checking is done with a voltmeter or ammeter.
Checking the valves is carried out with a voltage not higher than 12 V.
In the case of replacing the wiring of the electric generator, it is necessary to select wires of the same cross section and length.
Before checking the device, make sure that all connections are working and that the drive belt is properly tensioned. A belt is considered correctly tensioned, which, when pressed on the middle with a force of 10 kg / s, bends by no more than 10-15 mm.

How to check the generator with a multimeter or voltmeter?

Checking the voltage regulator

In order to check the voltage regulator, you will need a voltmeter with a scale from 0 to 15 V. Before starting the test, warm up the engine for 15 minutes at medium speed with the headlights on.
Measure the voltage between the terminals of the "mass" of the generator and "30" ("B+"). The voltmeter should show normal voltage for the particular vehicle. For example, for a VAZ 2108, it will correspond to - 13.5–14.6 V. If the voltage is lower or higher, most likely the regulator needs to be replaced.
In addition, you can check the regulated voltage by connecting a voltmeter to the terminals. It should be noted that the result of such a measurement will not be accurate if you are sure that the wiring is 100% correct. In this case, the motor should operate at medium speeds close to those with the headlights on and other consumers of electricity. The voltage size must match a certain value for a particular car model.

Checking the diode bridge of the generator

Turn on the voltmeter in the AC measurement mode and connect it to the "ground" and terminal "30" ("B+"). The voltage should be no more than 0.5 V, otherwise there is a possibility of diode failure.
To check the breakdown to "ground", it is necessary to disconnect the battery, as well as remove the generator wire that goes to the "30" ("B+") terminal.
Then connect the device between terminal "30" ("B+") and the disconnected wire of the generator. If the discharge current on the device exceeds -0.5 mA, it can be assumed that there is a breakdown of the diodes or the insulation of the generator diode windings.
The recoil current strength is checked using a special probe, which is an addition to the multimeter. It is something like a clamp or tongs, which covers the wires, thus measuring the strength of the current that passes through the wire.

Checking the recoil current

To measure the recoil current, you need to cover the wire with the probe, which goes to the terminal "30" ("B+").
Then, start the engine and take a measurement, during the measurement, the engine should run at high speeds. Turn on electrical appliances in turn and take measurements for each consumer separately.
Then count the readings.
The following test must be carried out with all power consumers switched on at the same time. The measurement value should not be lower than the sum of the readings of each of the consumers, when you measured each of them in turn, a discrepancy of 5 A downwards is allowed.

Checking the generator excitation current

To check the excitation current of the generator, start the engine and give it high speed.
Place the measuring probe around the wire connected to terminal 67 (“D +”), the readings on the device will correspond to the value of the excitation current, on a working generator it will be equal to - 3-7 A.

To check the excitation windings, you will need to remove the brush holder and voltage regulator. It may be necessary to clean the slip rings, also check for breaks in the winding or shorts to ground.

The functioning of the electrical equipment of the car depends on the reliable uninterrupted operation of power supplies. Their functions are performed:

Rechargeable battery when the engine is not running;
Generator when the power unit is running.

The battery also powers the starter when starting the internal combustion engine. However, the battery capacity is limited, the accumulated charge is sufficient to power consumers for a period of not more than 1-2 hours. The main load (including battery charging) falls on the car electric generator. The failure of the unit (especially on the road) is a serious problem, so the owner of the car should periodically check the health of the generator, troubleshoot in a timely manner, and take care of replacing the device in case of a serious threat to performance.

Possible causes of generator failure.

An automobile electric generator is a conventional DC or AC electrical machine. Automakers currently prefer a three-phase version with an independent supply of the excitation winding.

For electrical units, the following causes of malfunctions are typical:

Physical wear and aging of structural parts. The consequence is problems with the mechanics of the device (for example, shaft beats, jamming, up to the complete destruction of the winding part and housing), violation of the insulation of the windings, breaks in the conductors.
Exceeding the permissible thermal loads, due to which there is an accelerated destruction (up to complete burnout) of the insulation and disruption of the operation of other components (for example, brushes, built-in rectifiers, regulators).
Negative impact of the external environment. The most dangerous factors include temperature, humidity, dust, aggressive impurities (battery electrolyte fumes, road chemicals). Prolonged exposure leads to a violation of insulation, a decrease in the cross section of conductors in unprotected areas (for example, at contact points), the appearance of leaks, and the formation of unwanted conductive jumpers.

It is impossible to completely protect the device from the action of these factors during operation. However, following the rules of operation will reduce the risk of serious malfunctions.

If problems with electrical equipment could not be avoided, you should know how to independently check the generator and determine malfunctions.

Typical car alternator malfunctions.

The composition of the alternator includes:

A stator with a three-phase winding that creates a voltage of the required level.
A rotor with magnetic poles and an excitation winding that creates the magnetic flux necessary for generation. The winding is connected to collector slip rings.
A brush assembly equipped with graphite or metal-graphite brushes that provide contact with collector slip rings and supply voltage to the excitation winding.
Bearings and bushings that reduce mechanical resistance (friction) during rotation of the rotor.
Covers providing partial protection of the main structural elements.
Additional elements. These include a block of diode rectifiers, a relay-regulator. The first is designed to convert the alternating voltage of the generator into a constant voltage supplied to the on-board network to power consumers, charge the battery that feeds the excitation winding through the PP. The second regulates the excitation voltage, stabilizing the input voltage of the generator, cuts off the battery when the voltage goes beyond the limits allowed for the battery. These elements, although they are functionally independent, are structurally, in most cases, integrated with the electric generator.

Among the malfunctions of an automobile electric generator, there are problems of mechanics and electrical parts. The most typical are:

Damage or wear of the drive pulley;
Development (wear) or destruction of bearings or bushings of the rotor;
Wear (destruction of the surface) of the contact rings of the collector;
Abrasion or mechanical destruction of brushes;
Short circuit between slip rings;
Problems with the stator and rotor windings - breakage of conductors, short circuits between the turns of the windings, on metal parts of the structure;
Output from standing rectifier diodes;
Loss of efficiency of the relay-regulator.

These faults pose a serious danger to the electrical equipment of the car, especially the battery.

Signs of malfunctions.

The first, most alarming symptom of malfunctions is battery problems. Among them:

Flashing or constant glow of the battery discharge warning light on the dashboard;
Insufficient battery level, as a result of which it is difficult or impossible to start the starter and the internal combustion engine of the car;
Recharging the battery, accompanied by the boiling of the electrolyte, the formation of a characteristic coating on the contacts of the battery and auto parts.

In addition, problems with the power supply of on-board consumers are a clear sign, for example, a dim glow of lighting fixtures in the cabin and headlights. A change in the brightness of the lamps with a change in engine speed also indicates a malfunction of the onboard power supplies.

Often, mechanical problems are accompanied by "sound effects" - rattling, low squeaking or howling.

Self-diagnostics of the generator without dismantling from the car.

Often, malfunctions of the generator appear on a trip, when the car owner is deprived of the opportunity to dismantle the device on his own (many models require a special tool, free access from the bottom) and check the operation in detail. But superficial diagnostics, the determination of most of the problems that have arisen, can be carried out without removing the generator from the machine.

Preliminary check.

A preliminary check is made of parts that are not directly related to the generator, but that affect the performance:

Fuse in the battery charging circuit;
Drive belt.

The blown fuse is replaced. The same is done with the belt in the presence of cracks, bundles. The tension is checked by simply pressing the middle of the free area with your hand. With a deflection of more than 10-15 mm, adjustment with a tensioner will be required. In the case when the adjustment possibilities are not enough to eliminate, the belt is changed.

Often such actions are enough to restore normal battery charging. Otherwise, detailed diagnostics will be required.

General health check.

For diagnostics, you need a multimeter (tester) or a voltmeter with measurement limits up to 20 V. A universal device is preferable, since it may be needed for further testing of nodes.

The order of work is as follows:

Determine the voltage at the battery terminals with the engine off. A level of 12.3-12.7 V is considered normal (depending on many factors, such as temperature). A voltage of the order of 12 V and below indicates problems with charging and / or batteries and is a sufficient reason for a thorough check of the generator components.
Start and warm up the engine, re-measure. In the entire range of rotation speeds, the voltage should lie within 13.2-14.2 V. If the voltage does not rise to the specified values, the generator is inoperative, does not provide battery charge, or the charge circuits are broken. Exceeding the level of 14.5 V (for some cars 14.8 V) indicates problems with the relay-regulator, the need for further verification.

Often on Internet sites they describe a method of checking without measuring instruments. According to the proposed method, the engine is started, warmed up, then one of the battery terminals is disconnected. If the engine does not stall, the generator is functioning satisfactorily. Such a check is DANGEROUS for the electrical equipment of the car!

Even a slight inductance of the conductors connected to the battery terminals, when the current is interrupted (contacts are disconnected), becomes a source of voltage surge of short duration with a significant amplitude. Such a release can damage the on-board electronics, cause the devices to burn out. Car owners who decide to take such actions should remember that they can only be performed with the “negative” terminal of the battery, it is FORBIDDEN to disconnect the “plus”!

Another “folk” test is strictly prohibited - “for a spark” by a short circuit of the conductors connected to the output of the generator. The absence of current limits can damage rectifier diodes and other circuit elements!

Checking individual nodes.

If problems are found in the operation of the electric generator, it is necessary to check individual components in order to decide on further actions - the ability to continue driving (if a breakdown occurred during the trip), the need to repair or completely replace the device.

In general, if problems arise on the road, it is recommended to turn off the generator and get to the nearest service (on the battery, if there is enough charge) or in tow (tow truck). Operating a car with a faulty power supply can result in serious problems (for example, a complete failure of on-board electronics).

Mechanics check.

Wear of bushings and bearings, at first glance, seems to be the least serious problem. However, their wear leads to an increase in friction, overheating of the device, additional (albeit insignificant) power take-off of the engine. Distortions, destruction of parts, more complete jamming of the rotor, breakage of the drive belt are possible.

The integrity of the drive pulley is checked visually. To control the condition of the bearings (bushings), it is enough to turn the rotor manually, try to move it perpendicular to the axis of rotation. When parts are worn, a characteristic sound is heard, the rotor rotates with significant resistance. Play perpendicular to the axis is a sign of significant wear, indicating the need to replace parts.

Brush knot.

To check the brushes, it is enough to dismantle the brush assembly and visually inspect the parts. If the brushes are worn out, it is recommended to replace them. Before installation, check the condition of the collector.

Collector (slip rings).

The node is responsible for supplying the excitation voltage. Accordingly, significant wear of the collector rings is grafted to disruption of generation, instability of the output voltage. When brushes slide over the surface of worn rings, sparking is observed, which becomes a source of interference and malfunctions in the on-board electronics.

The condition of the rings is determined after dismantling the brush assembly visually (surface inspection) or by touch. A sign of significant wear is the sparking mentioned above.

The problem can be eliminated by grinding the surface of the collector rings (however, it cannot be carried out indefinitely - the thickness of the conductive layer is limited, as a result, the rotor will need to be replaced).

A short circuit between the rings is possible when current-carrying bridges are formed (from graphite or metal dust deposited when the brushes and rings actuate). Eliminated by cleaning the surface of the collector assembly.

Winding condition.

The power generator can:

Breakage of the phase windings of the stator, excitation windings.
Interturn short circuit;
Body break.

You can partially diagnose malfunctions using a tester. The device is used in the resistance measurement mode, the measurement limit is units of ohms. Before measurements, disconnect the connected conductors, remove the brushes.

Excitation winding check:

Measure the resistance between the collector rings. In the case of a good winding, the value is 2.3-5.1 ohms (nominal resistance 4.3 ohms). "Infinity" on an ohmmeter indicates a break, a smaller value is an indirect sign of an inter-turn short circuit.
Check the winding for an interturn short circuit. 12 V is supplied to the contact rings from the battery through a multimeter switched on in the DC current measurement mode (limit more than 5 A). Readings of more than 5 A indicate the presence of a short circuit between the turns.
Check the insulation breakdown by measuring the resistance between one of the collector rings and the housing. A value of more than 50 kOhm is a sign of breakdown.

Similar checks (except for breakdown verification) cannot be carried out without removing the device. First, it is required to disconnect the winding leads from the rectifier bridge. Secondly, their resistance is low, about 0.3 ohm, it is difficult to measure it without precision instruments.

Rectifier bridge.

The failure of the rectifier diodes is a fairly common malfunction that poses a serious danger. The breakdown of diodes is equivalent to a short circuit mode at the output of the generator, it creates shock current loads for the windings, overheating, insulation failure with further failure.

A detailed check, the determination of a burned-out diode, can only be carried out by removing the bridge. However, it will be possible to draw conclusions about the performance without dismantling the device.

For this:

Disconnect the wires, dismantle the brush assembly.
The tester (multimeter) measures the resistance between terminal B+ (30) and the case. The measurement limit is 1 kOhm, the “positive” probe is on B + (30). If the diodes are not broken, the measurement result is infinite resistance. Low resistance indicates breakdown of the bridge rack (the most common malfunction).
Change polarity (swap tester probes). Readings should correspond to a pair of open diodes (maximum within 200-500 ohms).
Similarly, they check an additional rectifier that feeds the relay-regulator - instead of terminal B + (30), the probe of the device is placed on contact D + (61).

A breakdown option is possible only for the diodes of the upper (lower) rectifier arm, the measurements described above do not determine the malfunction.

To diagnose the upper arm of the rectifier, they are carried out in the same way, but instead of the housing, the probe touches one of the bridge mounting bolts (windings are attached in these places). Low resistance in the first case (“positive” probe on B + (30) indicates a breakdown).

For the lower arm, measurements are taken between the mounting bolt and the device body. During breakdown, low resistance is obtained when the “positive” probe is located on the bolt, and the “negative” probe is on the body.

In the absence of a tester, a battery, a 10-15 W lamp and conductors are used. The "positive" probe corresponds to the wire connected to the "+" battery. The procedure is the same as above. When the resistance is low, the lamp lights up.

The car's battery supplies it with electricity in splendid isolation only before the engine starts. After starting the engine, a generator helps him. The task of the generator is to ensure continuous recharging of the battery in all operating modes and under any load on it. But breakdowns happen. How to determine that it is the generator that is to blame?

Signs of its malfunction are:

Nature of the fault	Cause of malfunction
The battery "boils out"	Large charging current
The battery is running low	Charging current is low or absent
The "No battery charge" lamp on the instrument panel of the car is on	No charge current
The voltage in the on-board network is unstable	There is no stabilization of the charge current or this current does not exist.
Extraneous sounds in the generator	Bearings require replacement or the alternator belt is not tensioned.

But first things first. The generator is not so easy to remove, and to do this, you need a good reason.

Diagnostics of the generator on the car with a multimeter / tester

Checked before checks tension and technical condition of the alternator belt. The belt must not be overtightened, but it must not be loosened either. In the first case, the bearings will wear out prematurely, in the second case, the rotor will slip with an increase in electrical load. Slippage, in addition to reducing the voltage in the network, will also lead to premature wear of the belt. The belt itself should not be worn and there should be no cracks on it.

If, when the engine is running, the smell of burnt rubber is felt from under the hood, the "lack of charge" lamp is on - seized alternator bearings. Increased noise, on the contrary, is caused by increasing the gap in them. This is checked by loosening the belt and shaking the rotor shaft in the radial direction. This determines only the play in the front bearing, but it also suffers in the first place.

If the mechanics are in order, check the electrical characteristics. This will require a device that can accurately measure a constant voltage of 12 - 16 V. Moreover, the scale (or digital indicator) at this measurement limit should show values \u200b\u200bin tenths, otherwise the measurements are meaningless. A pointer tester and a multimeter are also suitable.

The device is connected directly to the battery, observing the polarity. Polarity reversal will not harm digital devices, but for analog devices, the arrow will sharply hit the left limiter. You should not be afraid of this, the device will withstand it, but it is not advisable to stay in this position for a long time.

It is better to fix the measuring probes on the terminals. You can use the services of an assistant, but using crocodile clips is more convenient. The main requirement is that when the motor starts (it twitches at the same time), the clamps do not turn off spontaneously.

Before engine start fix the voltage of the battery. It should be within 12.5 - 12.7 V, depending on the degree of its charge, and the entire load is turned off. Do not forget that when you open the doors in the cabin, the light comes on, and this is at least a small, but a load. If the voltage is below 12 V, it is better to charge the battery before the test. A working regulator will greatly increase the voltage, trying to correct the situation and quickly charge the battery. And you will draw the wrong conclusions from this about its malfunction.

Now start the engine, warm it up so that the RPM equals the idle RPM for your model (usually within 800). We control the voltage on the battery, you can start looking at the scale of the device even during the warm-up process. The measured value must lie between 13.5 and 14 V. And so - in all modes of operation.

If at idle the voltage is below 13.0 V, then the problems may be as follows:

Faults related to broken contacts

It is necessary to constantly monitor the cleanliness of the battery terminals, but sandpaper cannot be used to clean oxides. It is better to scrape with a knife, and periodically loosen the contacts and grind the surfaces by turning the clamps on the terminal from side to side. And when checking the oil level, apply a couple of drops of it to the battery contacts.

Contact connections worth checking in case of low charge voltage:

Positive output: from the battery to the generator;
Negative output: from the battery to the car body; from the body of the car to the body of the engine.

Contact between the bodies of the car and the engine of VAZ models is provided flexible connection under the bottom in the area of the gearbox. The metal leash rots, additional resistance is added to the electrical circuit. And the minus of the generator is connected with the minus of the battery through it. Additional resistance is also introduced by rusty elements of the bodies of old cars.

The way out is to install an additional flexible connection from a 25mm2 conductor connected between any of the suitable bolted connections on the engine and the connection point of the battery negative terminal to the body.

Battery malfunctions

When sulfating the battery plates, depleting its resource charge voltage does not increase. The battery itself works as a limiter. To verify this, try to fully charge the battery. If it doesn't work out, replace it with a new one.

If during the operation of the generator the voltage on the battery is more than 14 V, then either it is very discharged, or the voltage regulator is faulty.

Diagnostics of the voltage regulator

The task of the voltage regulator is maintenance of battery voltage in the range from 13.5 to 14 V in all engine operating modes and under any load. Criteria for its performance:

When you press the gas pedal and increase the engine speed, the voltage rises slightly, without leaving the permissible limits.
When consumers are turned on: headlights, car radio, heater, air conditioner, the voltage drops below the permissible value only at idle. If at the same time increase the speed (add gas), then it returns to the operating range.

Check the operation of the regulator with the engine running, changing the number of revolutions by pressing the gas pedal. First, the experiment is carried out without load, then the headlights and the heater are turned on, adding a load. The voltage on the battery should not change significantly.

If this is not the case, the regulator is changed. On some models this is possible without removing the alternator, but it is still recommended to remove it. Purpose: to additionally assess the condition of the brushes, remove dirt accumulated during their operation, check the condition of the bearings.

Checking the generator brushes

For a detailed examination of the generator, it is removed from the car. Then it is cleaned of impurities. Remove the brush apparatus, if necessary - the voltage regulator. The brushes must be worn evenly (their length is the same, and the wear from the rotor rings is symmetrical about the longitudinal axis). The remaining length of the brushes should be more than 4.5 mm (8-10 mm is considered the norm). If these parameters are not met, the brushes are changed, even if the fault lies not in them.

Along the way, it will be necessary to remove the coal dust formed during the friction of the brushes on the rotor rings.

To replace the voltage regulator or brushes, further disassembly is not required, but if the fault has not yet been found, open the back cover of the generator. Before this, you will need to unwind the positive output pin.

Rectifier test

The generator generates a three-phase voltage rectified by six diodes. The positive and negative terminals of the rectifier are made in the form of aluminum plates, which at the same time are radiators for cooling the diodes.

To check their health, you will again need a multimeter or tester. We transfer the device to the resistance measurement mode. Then we alternately measure the resistance of each diode in the forward and reverse directions. To do this, change the polarity of connecting the probes of the device. In the forward direction, the resistance is small (but not zero). In reverse - equal to infinity. If this is not the case, the diode has failed.

If one diode is damaged, at least two more fail. Accidentally leaving a breakdown unattended will not work. They change the diodes in a group, together with the radiator.

Generator stator diagnostics

The stator winding is made with a thick wire, so breaks in it are rare. Unless the contacts are soldered at the points of its attachment to the diodes, which needs to be checked.

Then inspect the winding in search of mechanical damage. They appear if the rotor shaft shifted to the side during operation due to an increase in the output of bearings. At the same time, its impeller touches the turns of the stator winding and damages them. Result: breaks, coil shorts or ground shorts.

The insulation of the stator conductors is restored. To do this, a varnished cloth is laid between the turns. For fixing, the damaged area is coated with bakelite varnish and dried. The use of insulating tape is unacceptable, under the influence of the operating temperature inside the generator, it will melt.

In the absence of visible damage, it is possible that the turns of the winding short circuit between themselves and on the case. A turn short can only be detected by changing the color of a group of winding turns. It will not be possible to detect a defect by measurements, since the cross section of the wire is large, the number of turns, on the contrary, is small. The change in phase resistance is so small that it is comparable to the transition resistance at the point where the probes of the device are connected. But the probability of a turn circuit, fortunately, is small.

But short circuits on the case happen more often. To identify them, measure the resistance between any terminal of the winding and the housing. Use the highest limit of the multimeter to measure resistance. It is better to use a special device - a megohmmeter, but only on condition that the voltage it produces does not exceed 100 V. The operating voltage of the generator is 12-16 V, using a greater voltage to test megohmmeters will damage the insulation.

For any problems with the stator winding, the best way out is to replace it. The stator is sold with a winding wound inside it. And rewinding it yourself, even with the involvement of wrapping specialists, will not justify itself.

Diagnostics of the generator rotor

When inspecting the rotor, pay attention to:

development on slip rings: there should be no grooves formed under the brushes;
winding color: uniform, different from black (black color - the winding burned out).

To level the surfaces of slip rings, they can be ground by clamping the rotor in a lathe, be sure to center it. For grinding, sandpaper is used, the grain of which is reduced as it approaches the desired shape of the rings.

To diagnose the rotor winding, its resistance is measured with a multimeter or tester. For different models of generators, this value varies 2.3 to 5.1 ohms.

Alternator bearings

Pullers are used to remove bearings. The use of improvised means for this purpose is possible only with appropriate experience.

If during the diagnostics of the generator it turns out that more than two of its parts are to be replaced, it is better to purchase it as a whole. And if you are not confident in your abilities, immediately use the services of the specialists of the nearest service station. This will save you time, nerves, and possibly money.

We learn how to independently check the generator for performance. How to measure the voltage on the generator

How to test a car alternator with a multimeter

The stable and correct operation of the car's electronics largely depends on the health of the generator. It is he who provides power to all devices, and also helps to start the engine. In this regard, it is important to monitor its serviceability, and if necessary, know how to check the car's generator with a multimeter.

This element is directly related to the battery, which also often causes problems. And if necessary, connect new devices and various devices to the standard on-board network, you should check the health of the generator, since it is it that is the source of the standard current. In other words, this is one of those nodes that needs to be checked regularly.

Beginning of work

To start the test, no special preparations are required. You just need to prepare the multimeter itself. It is also advisable to check the generator - inspect the generator stator, diode bridge, voltage regulator, etc. This makes it possible to detect a malfunction at an early stage. In addition, an external inspection of other elements of the vehicle's electrical circuit should be carried out. Perhaps no further work is required.

So, the verification includes several stages:

Inspection of the relay-regulator.
Checking the diode bridge.

Relay-regulator

The relay-regulator maintains the optimal voltage value in the standard electrical circuit. In fact, it is precisely this that does not allow the voltage to increase to critical values. To carry out the test, start the engine, connect a multimeter and set the value "voltage measurement".

After that, it is necessary to measure the power supply of the on-board network directly at the battery terminals or at the contacts of the generator itself. Values must be between 14V and 14.2V.

Then you need to press the accelerator and take the measurement again.

The indicators should not change by more than 0.5 V. Otherwise, this will indicate incorrect operation.

The diode bridge consists of six individual diodes: half of them are positive, the other half are negative. It is necessary to select the "Continuity" mode on the multimeter. After that, as soon as the contacts close on the tester, a low beep will be heard. You need to check in both directions. If a squeak is heard in both cases, then this indicates a breakdown of the diode. Therefore, it needs to be replaced.

With the position of the multimeter probes, as in the following photos, the resistance should be infinite, if you swap the probes - within 700 ohms.

generator rotor

The rotor is a rod made of metal with an excitation winding. If you look at one of its ends, you can see special contact rings with sliding brushes.

First of all, it is necessary to remove the rod and conduct an external inspection of the winding, as well as bearings. In some cases, the problem is damage. If everything is in order, then you should proceed to check with a multimeter.

The device should be set to the "Measurement of resistance" mode. It should be checked between slip rings. This value should not be too large - this indicates the health and integrity of the winding.

It is quite difficult to carry out a detailed diagnosis of the rotor on your own, so if you suspect any problems, you should contact the auto repair shop.

The stator looks like a small cylinder, inside of which a winding is laid. The stator itself must be disconnected from the diode bridge before checking. First of all, you should carefully inspect the stator, as well as its individual elements for any damage. Particular attention should be paid to traces of possible burning.

Then you can check with a multimeter by setting the "Measurement of resistance" mode. With its help, breakdowns of the winding are detected. To do this, one contact should be connected to the body, and the other to the winding output.

In this case, the resistance must be very high, in fact, it tends to infinite values. If the readings are less than 50 KΩ, then this most likely indicates a malfunction of the stator and the entire generator.

Before starting the test, you should always find out in advance which particular generator set is on the car. For example, depending on the model of the machine, the relay-regulator can support different values in the range from 13.6–14.2 V. You need to know about this in advance, since in the end all this affects the final result of the test.

Otherwise, there are no particular difficulties, so it is quite possible to identify malfunctions or other problems that happen from time to time with the generator and other elements of the on-board electrical circuit on your own.

Video

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Read our other articles:

How to repair a VAZ generator

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How to check a car generator, proven methods

Checking the generator with a multimeter

You can check it yourself with a conventional tester turned on in ohmmeter mode (resistance measurement). First we check the rotor, then the stator and then the diode bridge. Let me remind you that the generator also has a brush assembly and a voltage regulator.

Sometimes these two nodes are structurally combined into one node. In general, begin inspections with a visual inspection of the brush assembly. After all, if the brushes do not reach the slip rings, then the unit will not produce electricity.

The simplest test of the charging system

Measure the battery voltage with the engine not running, if the battery is not discharged, then the voltage should be 12.5 - 12.8 volts. Now you need to start the engine and measure the voltage on the battery. Permissible voltage limits 13.5-14.5. The allowable maximum charge on some vehicles is 14.7 volts. Please note that if the battery is discharged, then the voltage at its terminals with the engine running may be higher.

Simple check on the car

A number of simple preliminary checks can be carried out without removing from the vehicle.

With the ignition off, use a test lamp (5W) to check for voltage on the B+ power wire. This wire is almost always directly connected to the battery positive. On some cars, it can go through a powerful fuse (from 60 amps and above).

Checking the alternator on a car also allows the use of a tester or multimeter. When the engine is running, turn on the maximum number of energy consumers and check the voltage on the battery. It should not fall below 12.8 volts.

With a multimeter in the resistance measurement mode, ring the excitation winding (on the rotor).

To do this, connect the measuring probes to the slip rings.

The resistance of a working winding should not be in the range of 2.3 -5.1 ohms.

If the resistance does not show at all, then there is a break in the winding.
If the resistance is lower than expected, then most likely an inter-turn circuit.
If it is higher, then there may be poor contact or the winding leads to the slip rings are not properly soldered.

We also measure the current consumed by the excitation winding. To do this, apply +12 volts to the slip rings and connect a DC ammeter to the circuit break. The current consumed by the winding should be in the range of 3-4.5 amperes. If the current is too high, then there is an interturn ignition in the rotor winding and it needs to be replaced. The maximum current of the relay-regulator is 5 amperes, therefore, with an overestimated current of the rotor winding, the voltage regulator also needs to be replaced.

Insulation resistance can be tested with a high alternating voltage of 220 volts by applying voltage through a 220 V, 40 W incandescent lamp, one contact is connected to the slip ring, the other to the metal housing of the rotor. In the absence of short circuits to the housing, the lamp should not burn. If the lamp filament glows even a little, then there is a current leakage to ground. This winding requires repair or replacement.

Take precautions when working with high voltage!

The stator windings can only be viewed by disconnecting or soldering the leads from the diode bridge. The resistance between the terminals of the windings should be approximately 0.2 Ohm. And between the output of any winding and 0 (common output) is about 0.3 ohms. If the stator windings or the diode bridge are closed, then the generator hums strongly during operation.

In the same way, the insulation test for breakdown is carried out through a lamp with a voltage of 220 volts. One contact is connected to the winding output, the second to the stator housing. With proper insulation, the lamp should not burn!

Also carefully inspect the condition of the internal parts of the stator and the outer part of the rotor. They should not come into contact with each other during operation. As the saying goes, "shoe". During this operation, the generator emits increased noise, which indicates wear on the bearings or bushings.

Video, check on a homemade stand:

The diode bridge consists of two plates, one of which is positive and the other is negative. Diodes are checked with a multimeter in ohmmeter mode.

Connect one probe to the “+” terminal of the diode bridge, and connect the second one in turn to the terminals F1 F2 F3 and 0. To make it clearer: we connect one probe to the positive plate, and with the other we alternately touch the terminals of those diodes that are pressed into this plate.

Then swap the probes and do the same. In one case, the tester should show conductivity (any resistance), but not in the other. Thus, we checked the diodes on the positive plate.

To check the diodes on the negative plate, we connect one probe to the negative plate, and the second to the diode leads in turn. In the same way, then we change the probes in places and repeat the procedure. In one case, the conductivity will be, in the other not.

Please note that the resistance should not be zero! This indicates a breakdown of the diode. Also, the breakdown of the diode is indicated by the absence of resistance in both directions when connected. A diode bridge, even with one faulty diode, will undercharge the battery, so it needs to be replaced.

Brushes and slip rings

Rings and brushes can be checked visually, evaluating their condition and serviceability. Check the protruding length of the brushes. It must be at least 4.5 mm. And normally 8-10 mm.

Also, the diameter of the slip rings must be at least 12.8 mm. and ideally 14.2-14.4. Worn out rings can be changed if you find them in a store. They are removed with a special puller, while the winding leads are soldered. After installing new rings, they can be machined on a lathe to eliminate runouts and sanded with fine sandpaper to eliminate burrs.

Engine lubrication system.

Ringing the generator winding with a multimeter

What to do if there is no light in the house? A power generator can help solve the problem. But if this equipment also fails, checking the generator with a multimeter will help determine the malfunction. Regardless of the type and brand, with the help of this device, having learned the cause of the malfunction, you can carry out simple repairs yourself.

There are a lot of varieties of generators, from large and powerful industrial ones to small automotive appliances. But the verification algorithm using the tester is the same for any generator.

What components and parts are checked with a multimeter

This operation provides for the diagnosis of the electrical part, while checking the following parts:

The performance of each of the listed operations requires special knowledge and skills for making measurements, so each check should be considered in more detail.

Output voltage level measurement

For each individual unit, this value will be different. Let's take a closer look at checking the car generator. We set the voltage measurement mode on the multimeter scale. First you need to check the voltage with the engine turned off. To do this, measure the voltage value at the battery terminals. We connect the red probe to the positive terminal, we fix the black one to the minus. A charged serviceable battery will give a value of up to 12.8 V. We start the engine. Then we take a measurement. Now this value should be no more than 14.8V, but not less than 13.5 V. If the voltage level is higher or lower, the generator is faulty.

Checking the rotor winding

To perform this operation, it is necessary to dismantle and disassemble the unit. When performing a self-test, do not forget to set the device to the circuit resistance measurement mode. Additionally, a value of no higher than 200 Ohm is set. These routine works are carried out in 2 stages:

Measurement of the resistance value of the rotor windings. To do this, we attach the probes to the rings of the moving part of the engine, determine the value. This will make it possible to determine the likelihood of a break in the winding circuit at a value above 5 ohms. If the device showed less than 1.9 ohms, a turn short circuit occurred. Most often, the circuit breaks at the junction of the output of the rotor winding to the ring. You can determine the defect by moving the wire at the soldering points with a probe, as well as when detecting darkened and crumbling wire insulation. In the event of a break and a short circuit (short circuit), the wires get very hot, so a breakdown can be detected by visual inspection.

The continuity is performed to detect a short circuit to the case. The generator rotor is conveniently located for work. Then we bring one probe to the rotor shaft, and attach the second to any ring. With a good winding, the resistance reading will go off scale. If it shows low resistance, this part should be sent for rewinding. When rewinding the rotor, it is important to maintain perfect balance.

Checking the stator windings

The stator test begins with a visual inspection. We pay attention to external damage to the case and insulation, places of burning wires during a short circuit.

The defective assembly should be rewound or replaced. With the external integrity of the wires, we begin to explore with a tester.

Advice! Before starting work, make sure that the unit is disconnected from the network, that there is no contact between the stator winding leads.

Performing work on checking the normal state of the node, we make sure:

In the integrity of the winding circuit. To do this, set the device to the resistance measurement mode. We fix the probes on the first pair of conclusions, then we check the 1st winding and the 3rd, 3rd and 2nd conclusions. If, during a break, the arrow of the analog device goes beyond the scale, the windings should be rewound.
In the absence of an interturn short circuit and to the case. To do this, we connect one of the tips to the output, the second - to the body. If the windings are closed, there will be a lower resistance value on the scale than on healthy ones.

Voltage Regulator Troubleshooting

Remove and disconnect the wires from the part. We inspect the condition of the brushes. They should not have significant defects and chips. In the guide channels of the brush holder, the generator brushes must move freely. If they protrude beyond the edge by less than 5 mm, the generator regulator should be changed.

The test is carried out using batteries and a 12-volt light bulb. The voltage of the second power source must be at least 15 V. Therefore, we connect the batteries in series to the car battery and bring the value to the desired one. Plus from the 1st power source we attach to the output contact, we fix the minus to ground.

The light bulb is installed between the brushes. When connecting a source of 16 V., it should not burn. With a weaker battery, it burns. In case of violation of proper combustion, the regulator should be replaced.

Checking the diode bridge and capacitor

The purpose of this node is to prevent the passage of electricity to the generator. He must direct it from the generator to the consumer. In this case, any deviation is a malfunction of the diode bridge. To check, we dismantle it and solder the conclusions on the generator. We expose the device to "ringing".

To check the power diode, we bring the black probe to the bridge plate, and attach the red probe to the output. When the multimeter reads 400-800 ohms, the diode is good, other numbers require replacement of the diode or bridge.

When checking the auxiliary diode, the operation is carried out similarly. But when changing the probes in places, the device should show the resistance value tending to infinity.

To detect a faulty capacitor, you can check it with the "old-fashioned method". To do this, you need to apply voltage to it for a short time. It must recharge. When its contacts are closed, a spark should pierce between them. This means that the capacitor is good.

When checking a polar capacitor, you need to remove the remaining charge. Then, on the scale, set the resistance measurement. The contacts must be attached with the correct polarity. When measuring a serviceable part, the resistance gradually increases. Otherwise, when the screen shows 0, it should be replaced.

If a non-polar capacitor is being tested, the MΩ is set on the value scale. We place the probes on the contacts, regardless of polarity. Then, you need to measure the resistance value. If the number on the screen is less than 2 ohms, this is a faulty part.

In conclusion, it must be recalled that all measurements when checking the generator's performance with a multimeter are carried out by measuring the resistance value of the electric current. Only to measure the voltage at the output of the generator, the device is configured to measure this value. Any beginner can check the generator with a multimeter. You just need to work with full responsibility and follow the instructions.

evosnab.ru

The main source of power in the car is the generator, it is such a "mini-power plant". Incorrect or unstable operation of this unit is fraught with poor battery charging. A failed generator does not provide charging, therefore, the on-board network of the car will work on a battery that will not last for a long time. As a result, the battery is completely discharged, the engine "stalls" somewhere outside the city, and you have a new "headache" and the need to replace the generator.

But before that, I consider it necessary to talk about precautions and certain rules that must be observed when checking this electrical appliance in order not to damage it.

It is forbidden:

Check the performance of the generator by short circuit, that is, "to a spark."
Connect terminal 30 (in some cases B+) to ground or terminal 67 (in some cases D+).
Allow the generator to work without consumers turned on, it is especially undesirable to work with the battery disconnected.
Carry out welding work on the car body with the wires of the generator and battery connected.

!!! Important:
Checking is done with a voltmeter or ammeter.
Checking the valves is carried out with a voltage not higher than 12 V.
In the case of replacing the wiring of the electric generator, it is necessary to select wires of the same cross section and length.
Before checking the device, make sure that all connections are working and that the drive belt is properly tensioned. A belt is considered to be correctly tensioned, which, when pressed on the middle with a force of 10 kgf, bends by no more than 10-15 mm.

How to check the generator with a multimeter or voltmeter?

Checking the voltage regulator

In order to check the voltage regulator, you will need a voltmeter with a scale from 0 to 15 V. Before starting the test, warm up the engine for 15 minutes at medium speed with the headlights on.
Measure the voltage between the terminals of the "mass" of the generator and "30" ("B+"). The voltmeter should show normal voltage for the particular vehicle. For example, for a VAZ 2108, it will correspond to - 13.5 - 14.6 V. If the voltage is lower or higher, most likely the regulator needs to be replaced.
In addition, you can check the regulated voltage by connecting a voltmeter to the battery terminals. It should be noted that the result of such a measurement will not be accurate if you are sure that the wiring is 100% correct. In this case, the motor should operate at medium speeds close to those with the headlights on and other consumers of electricity. The voltage size must match a certain value for a particular car model.

Checking the diode bridge of the generator

Turn on the voltmeter in the AC measurement mode and connect it to the "ground" and terminal "30" ("B+"). The voltage should be no more than 0.5 V, otherwise there is a possibility of diode failure.
To check the breakdown to "ground", it is necessary to disconnect the battery, as well as remove the generator wire that goes to the "30" ("B+") terminal.
Then connect the device between terminal "30" ("B+") and the disconnected wire of the generator. If the discharge current on the device exceeds -0.5 mA, it can be assumed that there is a breakdown of the diodes or the insulation of the generator diode windings.
The recoil current strength is checked using a special probe, which is an addition to the multimeter. It is something like a clamp or tongs, which covers the wires, thus measuring the strength of the current that passes through the wire.

Checking the recoil current

To measure the recoil current, you need to cover the wire with the probe, which goes to the terminal "30" ("B+").
Then, start the engine and take a measurement, during the measurement, the engine should run at high speeds. Turn on electrical appliances in turn and take measurements for each consumer separately.
Then count the readings.
The following test must be carried out with all power consumers switched on at the same time. The measurement value should not be lower than the sum of the readings of each of the consumers, when you measured each of them in turn, a discrepancy of 5 A downwards is allowed.

Checking the generator excitation current

To check the excitation current of the generator, start the engine and give it high speed.
Place the measuring probe around the wire connected to terminal 67 (“D +”), the readings on the device will correspond to the value of the excitation current, on a working generator it will be equal to - 3-7 A.

An ohmmeter is used for this test, its probes must be applied to the slip rings, the resistance value should be in the range of 5-10 ohms.
Then connect one ohmmeter probe to any contact ring, the second probe to the stator. On a working generator, the multimeter will show infinitely high resistance, otherwise, the excitation winding closes to ground.

Video how to check the car generator with your own hands:

Actual:

Driver's car allowance

www.autoposobie.ru

How to check the generator on the VAZ 2107 (photo and video)

Repair 15 January 2015 1122 0

The electrical equipment of a modern car is a complex set of instruments and devices. The on-board network is powered from the battery, and after starting the engine - from the generator. This device in good condition provides a voltage in the range of 14 - 14.2 V. Checking the VAZ 2107 generator will not only help identify its malfunctions, but also avoid battery failure.

With insufficient voltage, its charge becomes incomplete, which causes a drop in the density of the electrolyte. At low temperatures, this phenomenon can cause the liquid to freeze. The formation of ice crystals leads to the gradual destruction of the battery plates. To set the parameters of the output voltage, the generator can be called with a conventional multimeter.

Checking procedure for different engine operating modes

You will need an assistant to complete this operation. The sequence of actions to check the performance of the generator:

We set the digital or indicator multimeter to the DC voltage measurement mode. We check the parameters at the battery terminals. According to the instruction manual, the voltage should be in the range from 11.9 to 12.6 V, perhaps a little less, given that the network consumes a small amount of energy.
The assistant starts the engine and leaves it running at idle, check the voltage again. If it falls, this means that the generator is either not working at all, or the parameters are insufficient to charge the battery.
Exceeding the voltage value of 14.5 V for a long time will cause the electrolyte in the banks to boil.

If a generator malfunction is detected, it will be necessary to check the diode bridge, the electronic voltage regulator, the stator and rotor windings, as well as the condition of the brush assembly.

Component Health Monitoring

To perform this operation, it is necessary to dismantle the device from the car and clean it from dirt. The check procedure is as follows:

We transfer the multimeter to the resistance measurement mode. We install the positive probe on terminal "30", and the negative one on the ground. Readings close to zero indicate that the generator bridge or stator is out of order.
The check of positive diodes occurs when a positive probe is installed on the output of one of the rectifier unit fastening bolts, and the negative probe is connected to ground. Zero or close readings of the device indicate that the diode bridge is faulty.
To check the rotor, it is necessary to measure the resistance between the slip rings. In working condition, it should be within a few ohms. If the resistance is near zero, then a short circuit has occurred in the winding.

The diode bridge and other faulty elements of the generator must be replaced with new ones from spare parts.

7vaz.ru

How to check the generator voltage regulator yourself

An indispensable and one of the most important components of each car is a generator, which is a kind of mini-power plant. This is the main source of electrical power, unstable or incorrect operation of which will cause the battery to charge poorly or not at all. Therefore, every driver must be sure that the generator on his car is working properly. To do this, it is necessary to carry out periodic diagnostics of this device. In this article I will tell you how to independently check the generator on a car.

It is not difficult to guess that the ideal place to check the generator is the service station. But this does not mean at all that it is impossible to check his condition at home with the help of his own knowledge, skills and strengths.

Before proceeding with the diagnosis of a car generator, you should acquire a special device designed to measure voltage. It's about a multimeter.
In some sources, there may be a recommendation regarding the mandatory presence of a tester, avometer, voltmeter, ammeter, but I declare with confidence that all these devices are actually the same, and minor differences are only in a set of additional functions. Therefore, in principle, each of the previously listed devices will be the correct answer to the question of how to check the voltage on the generator.

In the process of checking the mini-electric power station of each car, the driver must know and remember what not to do:

Someone's help will be needed. This person will not have to do anything special, so it is not necessary to look for a specialist in the field of cars. Just the case when even a woman can be allowed to approach the car.
The valves of the analyzed device should be checked using a voltage that does not exceed 12 V.
If it is necessary to replace the generator wiring, it is imperative to select only those wires that have similar cross-sectional and length indicators.
Immediately before diagnosing all the elements of the generator, I recommend checking the serviceability of all its connections and the tension of its belt. If everything is clear with the first point, then the second one needs to be specified. The belt is considered to be tensioned correctly only if, when pressed with a force of 10 kgf on its middle, it bends by 10-15 mm - and no more than that.

Check instruction

Diagnosing a generator is not an easy task, so here you need to follow a certain sequence of actions. First of all, it is necessary to check the generator relay, after - the diode bridge, then - the stator and, finally, the rotor. I advise in this situation not to improvise, but to strictly adhere to the instructions given.

Relay

The fact of overvoltage in the area of \u200b\u200bthe vehicle's on-board network can cause the operation of more than one device to stop. The generator regulator relay is needed in order to maintain the correct potential difference. To check if this device is functioning normally, you need:

Switch the multimeter to voltage measurement mode.
Start car.
Measure the voltage level at the battery terminals or at the generator outputs. The optimal value should fluctuate around 14-14.2 V.
Press the accelerator (this is where the assistant mentioned earlier comes in handy). The voltage level should not change by more than 0.5 V. If this is not the case, then we can confidently talk about a malfunction of the relay-regulator.

This device consists of six diodes, which are combined into a plate, of which one is negative and the second is positive. Three diodes have ground at the cathode and the rest at the anode. You can check the diode post according to this scheme:

Car owners should pay attention to the fact that the resistance should in no case be equal to zero. If so, then there is a possibility of breakdown of the diode. The absence of any resistance in both directions during the connection process can also tell about the diode breakdown. The diode bridge is capable of distributing undercharging even with the fact of one faulty diode, therefore, in this case, the car needs an urgent replacement of this mechanism.

stator

This block has the form of a hollow metal cylinder, inside which generator windings are neatly stacked. The instruction for checking this unit is as follows:

Disconnect the starter leads from the diode bridge.
Inspect the condition of the winding, because it should not have any kind of damage or burning.
Set the multimeter to resistance measurement mode.
Check the winding for breakdowns: measure the resistance level between the stator housing and any of the winding leads. This value, oddly enough, falls into the category where more is better. Ideal when it tends to infinity. And if the device shows a value that is below 50 KΩ, this indicates an imminent failure of the entire oscillator.

Rotor

This node is made in the form of a metal rod. On which the winding is just wound, and rings are attached to its ends, along which the generator brushes slide.
To diagnose this mechanism, follow these recommendations:

I recommend removing the rotor and inspecting the condition of the bearings and windings.
Connect the test leads to the slip rings (the multimeter must still be in resistance measurement mode). The value of this indicator should be in the range of 2.3-5.1 ohms.
Inconsistency with the indicator: the resistance does not show at all - a break has occurred in the winding; the resistance is higher - poor contact is possible, or the fact is that the winding leads are not soldered properly to the rings; lower resistance - the possibility of interturn circuit.

The above instruction for diagnosing a car generator will help in time to identify malfunctions in its operation in the so-called field conditions. And this will prevent many problems in the general condition of the car. By the way, this algorithm will find application when checking most modern cars, as well as many domestic ones. But, I repeat, the main condition is that the voltage of the on-board network is 12 V.

Video "Diagnosis and repair of generators"

Video on diagnosing malfunctions in automotive generators.

mineavto.ru

How to check the generator for performance using a multimeter

The generator is quite stable in operation. Its failure, as a rule, occurs due to environmental factors, for example, in the form of condensing moisture on contacts and metal, which causes corrosion and breakdowns, as well as as a result of mechanical wear of rotating parts.

To know how to check the charging of the generator, you need some basic knowledge about the device of the unit, its components and the concept of operation of some of its parts.

To measure electrical resistance, you will need a special control and measuring apparatus: the so-called multimeter or ohmmeter.

How to check the generator stator for the integrity of its winding

Before checking the generator winding with a tester, it is necessary, first of all, to inspect it for external damage to the insulation, burns in the winding resulting from short circuits. If damage is visible to the eye, the stator must be replaced. If no external damage is found, then we proceed to a step-by-step check of the integrity of the stator winding using an ohmmeter.

The stator must be disconnected, the winding leads must not come into contact with each other.

Need to check:

no open circuit winding
lack of short circuit of the windings with the body.

We put an ohmmeter on the dial and measure the resistance.

In the first case, the ohmmeter tips are connected in turn to each of the three winding leads. With a faulty winding, the control device will show infinite resistance (i.e. one in the left digit of the digital multimeter and the maximum deviation to the right if the multimeter is analog).

There are two schematic diagrams of how to connect the generator to the network at home - with a changeover switch or through automatic control. At the same time, it is very important to comply with the established safety rules when operating home power plants.

Along with checking the generator, it is often necessary to test the car's battery for performance. All verification methods can be found here.

In the second case, the ohmmeter tips are connected to the winding output and to the stator housing. In the presence of a short circuit, the control device should show a low resistance.

A serviceable stator, therefore, in these two tests should show a small resistance in the first case and an infinitely large one in the second.

Checking the health of the voltage regulator in the generator

Before checking the generator voltage regulator, it must be dismantled and disconnected. Next, you need to make sure that the brushes are intact, have no defects and chips, and move freely in the channels of the brush holder. Brushes protruding less than 4.5 mm require replacement of the voltage regulator.

The voltage regulator is directly checked using additional power sources: 12-14 V and 16-22 V.

Accordingly, the first source can be a battery, the second source is a battery with 1.5-volt batteries connected in series to it.

The positive output of the battery is connected to the output of the device, the negative - to the mass of the voltage regulator. A 12-volt light bulb is connected between the brushes.

If the regulator is in good condition when voltage is applied:

12-14 V light bulb should be on;
16-22 V, the light should go out.

In all other cases, the voltage regulator is defective, cannot be repaired and must be replaced with a new one.

Checking the capacitor for performance

A rough check of the capacitor can be carried out by charging it for several seconds with a voltage not exceeding the maximum indicated on it, after which closing its contacts with an iron object insulated from the hands. If the capacitor is in good condition, i.e. with its ability to charge and store a charge, a spark should appear.

Before you check the capacitor with a multimeter, you need to clarify that they are polar, i.e. which must be connected strictly in accordance with the polarity indicated on the outputs, and non-polar.

Polar capacitor test.

First, we close the contacts of the capacitor, removing the charge stored in it. It is necessary to put the control device on the ringing and measurement of resistance. Then we connect the ohmmeter contacts in accordance with the polarity of the capacitor. A serviceable capacitor begins to charge, the resistance indicator will increase until it starts to go to infinity. Such results for a working capacitor.

For the arrangement of channels for wiring and pipelines, a wall chaser is used. This tool does not have to be purchased ready-made in the store. It will be much more economical to make a do-it-yourself bar cutter from a grinder and other improvised elements.

It will be useful for any radio amateur and electrician to know the different characteristics of small parts and other electrical equipment. For example, you can read about the principles of operation of a power regulator on a triac here, and this article reveals the features of the color marking of resistors.

A non-working capacitor will:

cause the ohmmeter to squeak and show zero resistance;
immediately show infinite resistance.

Non-polar capacitor test.

We set the megaohm values on the control device and touch it with the contacts of the capacitor leads. At low resistance values (less than 2 mΩ), the capacitor is most likely in a non-working state.

Checking the diode bridge of the generator with a multimeter

The task of rectifier diodes is to correctly pass current in the direction from the generator and block its passage in the opposite direction. Any deviation in its operation is considered a failure of the diode bridge. Let's take a closer look at how to check the diode bridge of the generator.

First you need to remove the diode bridge from the generator and disassemble it to gain access to the diode contacts. The soldered leads on the stator need to be unsoldered.

The multimeter switch must be set to ring. Diodes are semiconductors, belong to microelectronics. To ring a diode bridge, you need to understand its structure and have a circuit diagram.

Checking power diodes.

The negative terminal of the multimeter is connected to the plate of the diode bridge, the positive terminal is connected to the diode output. The current must pass. The instrument readings should tend to infinity. We connect the positive probe of the multimeter to the plate of the diode bridge, the negative one - to the output of the diode. The multimeter should show a resistance of 400 to 800 ohms.

Checking auxiliary diodes.

We connect the negative output of the multimeter to the auxiliary diode plate, the positive output to the diode output. The multimeter should show a value between 400 and 800 ohms. We connect the positive contact of the multimeter to the auxiliary diode plate, the negative contact to the diode output. The instrument readings will tend to infinite resistance.

Bearing inspection

A bearing is a mechanical part whose failure is due to a change in its physical properties. These can be corrosion, cracks, wear, damage, backlash, difficulty in rotation. An external sign of a problem with the generator bearing is the hum and noise emitted by the generator.

In this case, the rear bearing is removed and examined for the aforementioned part defects. The bearing ring must be able to rotate freely without creating extraneous noise.

If we talk about a car generator, then its front bearing is usually mounted in a cover. Checking is carried out according to a similar principle, rotating the cover and holding the center. The bearing should not seize or make noise.

Bearings with poor rotation or misalignment must be replaced.

Thus, checking the generator for operability is not very difficult. The main thing is to understand the essence of the processes occurring in the device. The fundamental problems that happen to the generator are simple and standard. Armed with a multimeter and the knowledge gained, you can easily find a malfunction in the generator.

Resistance formula through voltage

Series Voltage

DC voltage

How to assemble a circuit with a stable voltage of 6 volts

Checking the generator with a multimeter

The simplest test of the charging system

Measure battery voltage at not running engine, if not discharged, then the voltage should be 12.5 - 12.8 volts. Now you need to start the engine and measure the voltage on the battery. Permissible voltage limits 13.5-14.5. The allowable maximum charge on some vehicles is 14.7 volts. Please note that if the battery is discharged, then the voltage at its terminals with the engine running may be higher.

Simple check on the car

A number of simple preliminary checks can be carried out without removing from the vehicle.

Rotor check

With a multimeter in the resistance measurement mode, ring the excitation winding (on the rotor).

To do this, connect the measuring probes to the slip rings.

The resistance of a working winding should not be in the range of 2.3 -5.1 ohms.

If the resistance does not show at all, then there is a break in the winding.
If the resistance is lower than expected, then most likely an inter-turn circuit.
If it is higher, then there may be poor contact or the winding leads to the slip rings are not properly soldered.

Insulation resistance can be tested with high AC voltage 220 volt, applying voltage through an incandescent lamp 220 V, 40 W., we connect one contact to the slip ring, the other to the metal housing of the rotor. In the absence of short circuits on the case the lamp should not be on.. If the lamp filament glows even a little, then there is a current leakage to ground. This winding requires repair or replacement.

Take precautions when working with high voltage!

generator stator

Video, check on a homemade stand:

Diode bridge

The diode bridge consists of two plates, one of which is positive and the other is negative. Diodes are checked with a multimeter in ohmmeter mode.

Connect one probe to the terminal «+ » diode bridge, and the second alternately connect to the terminals F1 F2 F3 and 0. To make it clearer: we connect one probe to the positive plate, and with the other we alternately touch the terminals of those diodes that are pressed into this plate.

Then swap the probes and do the same. In one case, the tester should show conductivity (any resistance), but not in the other. Thus, we checked the diodes on the positive plate.

Brushes and slip rings

Rings and brushes can be checked visually, evaluating their condition and serviceability. Check the protruding length of the brushes. It must be at least 4.5 mm. And normally 8-10 mm.