We are learning how to independently check the generator for performance. How to measure voltage on a generator

How to check a car generator with a multimeter

Stable and correct operation of the car electronics largely depends on the condition 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 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, check the generator's serviceability, since it is he who is the source of the standard current. In other words, this is one of those nodes that need to be checked regularly.

Beginning of work

No special preparations are required to start testing. 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 identify a malfunction at an early stage. In addition, an external inspection of other elements of the car's electrical circuit should be carried out. Perhaps no further work is required.

So, the check includes several stages:

1. Inspection of the relay-regulator.
2. 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 rise to critical values. To carry out the test, start the engine, connect a multimeter and set the "voltage measurement" value.

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

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.

A diode bridge consists of six separate diodes: half of them are positive, the other half are negative. It is necessary to select the "Call" mode on the multimeter. After that, as soon as the contacts are closed on the tester, you will hear a soft squeak. You need to check in both directions. If a squeak is heard in either case, then this indicates a breakdown of the diode. Therefore, it needs to be replaced.

With the position of the probes of the multimeter, 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 a field 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 the bearings. In some cases, the problem is damage. If everything is in order, then you should proceed to checking with a multimeter.

The device should be set to the "Resistance measurement" mode. It should be checked between the 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 detailed diagnostics 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 with a winding inside it. 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. Pay particular attention to traces of possible burning.

Then you can check with a multimeter by setting the "Resistance measurement" mode. With its help, winding breakdowns are detected. To do this, one contact should be connected to the case, and the other to the winding terminal.

In this case, the resistance should 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 generator set is on the vehicle. For example, depending on the model of the machine, the relay-regulator can maintain 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 special difficulties, therefore, on our own 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.

Video

For more information, watch the video:

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 independently check with a conventional tester, included in the 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 units are structurally combined into one unit. In general, start your checks by visually inspecting the brush assembly. After all, if the brushes do not reach the slip rings, then the unit will not produce electricity.

Easiest Charging System Check

Measure the voltage of the battery 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. Allowable voltage limits are 13.5-14.5. The permissible maximum charging 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 car check

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

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

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

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

To do this, attach the test leads to the slip rings.

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

• If the resistance does not show at all, then there is an open circuit in the winding.
• If the resistance is below the specified value, 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 soldered properly.

We also measure the current consumed by the excitation winding. To do this, we supply +12 volts to the slip rings and connect a DC ammeter to the open circuit. The current consumed by the winding should be within 3-4.5 Amperes. If the current is too high, it means that there is interturn ignition in the rotor winding and it needs to be replaced. The maximum current of the relay-regulator is 5 Amperes, therefore, if the current of the rotor winding is too high, the voltage regulator must also be replaced.

The insulation resistance can be checked 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 rotor body. If there are no short circuits to the case, the lamp should not burn. If the filament of the lamp glows even a little, then there is a current leakage to the ground. Such a winding requires repair or replacement.

Observe precautions when working with high voltages!

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

In the same way, a breakdown test of insulation is carried out through a 220-volt lamp. One contact is connected to the winding terminal, the second to the stator housing. If the insulation is in good condition, the lamp should not burn!

Also carefully inspect the condition of the inner parts of the stator and the outer part of the rotor. They should not touch 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 at a homemade stand:

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

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

Then swap the test leads and do the same. In one case, the tester should show conductivity (some kind of resistance), and in the other not. 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 one to the diode terminals in turn. In the same way, then we change the probes in places and repeat the procedure. In one case, there will be conductivity, in the other not.

Please note that the resistance must 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 to assess their condition and serviceability. Check the protruding length of the brushes. It must be at least 4.5 mm. And normally it is 8-10 mm.

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

Engine lubrication system device.

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Checking the generator winding with a multimeter

What if there is no light in the house? A current generator can help in solving 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, using this device, having learned the cause of the malfunction, you can carry out simple repairs yourself.

There are many types of generators, from large and powerful industrial devices to small automotive devices. But the algorithm for checking with the tester is the same for any generator.

What components and parts are checked with a multimeter

This operation involves diagnostics of the electrical part, while checking the following parts:

Each of the above operations requires special knowledge and skills to make measurements, so each check should be considered in more detail.

Measuring the output voltage level

This value will be different for each individual unit. Let's take a closer look at checking a car generator. We set the voltage measurement mode on the multimeter scale. First, you need to check the voltage with the engine off. To do this, we measure the voltage value at the battery terminals. We connect the red probe to the positive terminal, 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 the measurement. Now this value should be no more than 14.8V, but not less than 13.5V. 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 your own test, do not forget to set the device to the mode of measuring the resistance of the circuit. Additionally, the value of the value is not higher than 200 Ohm. These routine maintenance is carried out in 2 stages:

1. Measurement of the resistance value of the rotor windings. To do this, attach the probes to the rings of the moving part of the engine, determine the value. This will make it possible to determine the probability of a break in the winding circuit at a value above 5 ohms. If the device reads less than 1.9 ohms, a turn circuit has occurred. Most often, the chain breaks at the junction of the rotor winding lead to the ring. It is possible to determine the defect by moving the wire with the probe at the soldering points, as well as by detecting darkened and crumbling wire insulation. In the event of an open circuit and short circuit (short circuit), the wires get very hot, so a breakdown can be detected by visual inspection.
2. A continuity test is performed to detect a short to ground. We position the rotor of the generator conveniently for work. Then we bring one probe to the rotor shaft, the second we attach to any ring. With a good winding, the resistance reading will go off scale. If it shows little resistance, this part should be rewound. When rewinding the rotor, it is important to maintain perfect balance.

Checking the stator windings

Inspection of the stator begins with a visual inspection. We draw attention to external damage to the case and insulation, places where wires are burned during a short circuit.

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

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

Performing the work on checking the normal state of the node, we are convinced:

• In the integrity of the winding circuit. To do this, set the device to the resistance measurement mode. We attach the probes to the first pair of leads, then check the 1st winding and the 3rd, 3rd and 2nd leads. If, upon a break, the arrow of the analog device goes beyond the scale, rewind the windings.
• In the absence of turn-to-turn short circuit and on the case. To do this, we connect one of the tips to the terminal, the second to the body. If the windings are closed, the scale will have a lower resistance value than the serviceable ones.

Troubleshooting the voltage regulator

We 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. When they protrude beyond the edge 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 value. We attach the plus from the 1st power supply to the output contact, and fix the minus to the ground.

A light bulb is installed between the brushes. When a 16 V source is connected, it should not light up. With a weaker battery, it will burn. If proper combustion is disturbed, the regulator should be replaced.

Diode bridge and capacitor test

The task of this unit 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 unsolder the leads on the generator. We set the device to "ringing".

To check the power diode, we bring the black probe to the bridge plate, and attach the red one to the output. When the multimeter reads 400-800 Ohm - the diode is working, other numbers require replacing the diode or bridge.

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

To detect a defective 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 should be charged. When its contacts are closed, a spark should break through between them. This means that the capacitor is working properly.

When checking a polar capacitor, the remaining charge must be removed. Then, on the scale, we set the resistance measurement. Contacts must be secured with correct polarity. When measuring a serviceable part, the resistance gradually increases. Otherwise, when 0 appears on the screen, it should be replaced.

If a non-polar capacitor is tested, the value scale is set to MΩ. 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 value of the resistance of the electric current. For measuring the voltage at the generator output only, the instrument is set up to measure this quantity. 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 power source in the car is the generator, it is a kind of "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.

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

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

It is forbidden:

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

• !!! Important:
• Checking is done using a voltmeter or ammeter.
• Valves are checked with a voltage not exceeding 12 V.
• In the case of replacing the wiring of the 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 correctly tensioned. A belt is considered to be correctly tensioned, which, when pressed into 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

1. In order to check the voltage regulator, you will need a voltmeter with a scale from 0 to 15 V. Before starting the test, you should warm up the engine for 15 minutes at medium speed with the headlights on.
2. Measure the voltage between the generator “ground” terminals and “30” (“B +”). The voltmeter should show the voltage normal for a 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.
3. In addition, you can check the regulated voltage, for this, connect a voltmeter to the battery terminals. It should be noted that this measurement will be inaccurate if you are confident that the wiring is 100% good. At the same time, the motor must operate at medium speeds close with the headlights on and other electricity consumers. The voltage size must match a certain value for a specific car model.

Checking the diode bridge of the generator

1. Switch on the voltmeter to the alternating current measurement mode and connect it to "mass" and terminal "30" ("B +"). The voltage should be no more than 0.5 V, otherwise there is a possibility of diode malfunction.
2. To check the breakdown to "ground", it is necessary to disconnect the battery, and also remove the generator wire, which goes to the terminal "30" ("B +").
3. 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 insulation of the generator diode windings.
4. The recoil current is checked using a special probe, which is an addition to the multimeter. It is something like a clamp or pincer that covers the wires, thus measuring the current flowing through the wire.

Checking the recoil current

1. To measure the recoil current, you need to cover the wire with the probe, which goes to the "30" ("B +") terminal.
2. Then, start the engine and take the measurement; during the measurement, the motor should run at high rpm. Turn on electrical appliances in turn and take measurements for each consumer separately.
3. Then count the readings.
4. The next 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 consumer, when you measured each of them in turn, a discrepancy of 5 A in the lower direction is allowed.

Checking the generator excitation current

1. To check the excitation current of the generator, start the motor and run it at high revs.
2. 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 - 3-7 A.

To check the field windings, you will need to remove the brush holder and voltage regulator. You may need to clean the slip rings, also check for breaks in the winding or short circuits to ground.

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

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

Driver's car manual

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

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 working order, provides a voltage in the range of 14 - 14.2 V. Checking the VAZ 2107 generator will not only help to identify its malfunctions, but also to avoid the failure of the battery.

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

Checking procedure for different engine operating modes

To perform this operation, you will need an assistant. The sequence of actions for checking the generator's performance:

1. 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, possibly a little less, given that the network consumes a small amount of energy.
2. The assistant starts the engine and leaves it at idle speed, check the voltage again. If it falls, this means that the generator is either completely not working, or the parameters are insufficient to charge the battery.
3. If the voltage exceeds the value of 14.5 V for a long time, the electrolyte in the cans will boil.

If a generator malfunction is detected, it will be necessary to check the diode bridge, electronic voltage regulator, 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:

1. We transfer the multimeter to the resistance measurement mode. We install the positive probe to the "30" terminal, and the negative one to the ground. Readings close to zero indicate that the bridge or generator stator is out of order.
2. Checking the positive diodes occurs when the positive probe is installed on the output of one of the rectifier block mounting bolts, and the negative one to ground. Zero or close to them readings of the device indicate that the diode bridge is faulty.
3. 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 about 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 the spare parts.

7vaz.ru

How to check the generator voltage regulator yourself

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

It is not hard to guess that a workshop is the ideal place to check a generator. 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 powers.

Before you start diagnosing a car generator, you should get a special device designed to measure voltage. This is 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 the 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-power plant of each car, the driver must know and remember what cannot be done:

• Someone will need help. 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 the car.
• The valves of the analyzed device should be checked using a voltage that does not exceed the 12 V mark.
• If it is necessary to replace the generator wiring, but it is imperative to choose only those wires that have the same cross-section and length.
• Immediately before diagnosing all 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 concretized. The belt is considered tensioned correctly only if, when pressed with a force of 10 kgf to its middle, it bends by 10-15 mm - and no more.

Verification instruction

Generator diagnostics is not an easy task, so you need to adhere to 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 ​​the vehicle's on-board network may cause the termination of the operation of more than one device. The generator relay regulator is needed in order to maintain the correct potential difference. To check if this device is functioning normally, you need:

1. Switch the multimeter to voltage measurement mode.
2. Start the car.
3. Measure the voltage level at the battery terminals or at the generator outputs. The optimal value should fluctuate around 14-14.2 V.
4. Click on 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 other is positive. Three diodes have a mass at the cathode, and the rest are at the anode. You can check the diode post according to this scheme:

Car owners should pay attention to the fact that resistance should never be zero. If this is the case, then there is a possibility of diode breakdown. The fact that there is no resistance in both directions during the connection process can also indicate a diode breakdown. The diode bridge is capable of 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 looks like a hollow metal cylinder, inside which the generator windings are neatly laid. The instruction for checking this unit looks like this:

• Disconnect starter leads from diode bridge.
• Inspect the condition of the winding, because it should not have any kind of damage or burning.
• Put the multimeter in 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 the more the 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 autogenerator.

Rotor

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

1. I recommend removing the rotor and inspecting the condition of the bearings and windings.
2. 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.
3. Inconsistency with the indicator: the resistance does not show at all - an open circuit has occurred in the winding; the resistance is higher - poor contact is possible, or the fact is that the winding leads are not properly soldered to the rings; resistance below - the possibility of turn-to-turn closure.

The above instructions for diagnosing a car generator will help to identify faults in its operation in the so-called field conditions in time. And this will be the reason for the prevention of 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 "Diagnostics and repair of generators"

Video about diagnostics of malfunctions in automobile generators.

mineavto.ru

How to check the generator for operation with a multimeter

The generator is quite stable in operation. Its failure, as a rule, occurs due to environmental influences, for example, in the form of condensed moisture on the 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 constituent components and the schematic diagram of the operation of some of its parts.

To measure electrical resistance, you will need a special measuring device: a so-called multimeter or ohmmeter.

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

Before you check the generator winding with a tester, you must first of all 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.

You want to check:

• no open circuit of the winding
• lack of short circuit of the windings with the case.

We put an ohmmeter on ringing and measuring resistance.

In the first case, the ohmmeter tips are connected alternately to each of the three winding leads. If the winding is faulty, 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).

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

In the second case, the ohmmeter tips are connected to the winding terminal and to the stator case. If there is a short circuit, the tester should show a low resistance.

A serviceable stator, therefore, in these two tests should show low resistance in the first case and infinitely large - in the second.

Checking the serviceability 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 or chips, and move freely in the channels of the brush holder. If the brushes protrude less than 4.5 mm, the voltage regulator must be replaced.

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 output to the ground of the voltage regulator. A 12 volt light bulb is connected between the brushes.

If the regulator is working properly when voltage is applied:

• 12-14 V light should be on;
• 16-22 V the lamp should go out.

In all other cases, the voltage regulator is faulty, 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 a few seconds with a voltage not exceeding the maximum indicated on it, after which closing its contacts with an iron object isolated from the hands. If the capacitor is in good working order, i.e. with its ability to charge and store a charge, a spark should appear.

Before checking the capacitor with a multimeter, it is necessary 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 set the control device to ring and measure the resistance. Then we connect the ohmmeter contacts in accordance with the polarity of the capacitor. A working capacitor begins to charge, the resistance indicator will grow until it begins to tend to infinity. These are the results for a working capacitor.

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

A non-working capacitor will be:

• 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 terminals. At low resistance values ​​(less than 2 mΩ), the capacitor is most likely in an inoperative state.

Checking the diode bridge of the generator with a multimeter

The task of the 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 malfunction of a 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 must be unsoldered.

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

Checking power diodes.

The negative terminal of the multimeter is connected to the diode bridge plate, the positive terminal is connected to the diode terminal. The current must pass. The readings of the device 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 between 400 and 800 ohms.

Testing of auxiliary diodes.

The negative output of the multimeter is connected to the plate of auxiliary diodes, the positive output is connected to the output of the diode. 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 terminal. The meter reading will tend to infinite resistance.

Bearing inspection

A bearing is a mechanical part, the failure of which is a change in its physical properties. These can be corrosion, cracks, wear, damage, backlash, difficulty in rotation. An outward symptom of a generator bearing problem is hum and noise emitted by the generator.

In this case, the rear bearing is removed and examined for the aforementioned defects in the part. The bearing ring must rotate freely without generating abnormal noise.

If we talk about an automobile generator, then its front bearing is usually built into the cover. Checking is carried out in a similar way, rotating the lid and holding the center. The bearing must not seize or make noise.

A bearing with poor rotation or deflection in the axis of rotation must be replaced.

Thus, checking the generator for operability is not very difficult. The main thing is to understand the essence of the processes taking place in the device. The fundamental problems that happen with a 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

Serial voltage

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

The generator is the main source of current that powers the electrical appliances of the vehicle. A malfunctioning car generator leads to insufficient battery charging, which leads to a voltage drop, blackout and a complete stop of the operation of electrical appliances. For this reason, it is necessary to regularly check the condition of the generator and immediately respond to malfunctions in its operation.

Signs of mechanical damage to the generator

The presence of extraneous noise can also be a consequence of the turn-to-turn closure of the stator winding. In a similar way, a malfunction of the connections and contacts, a short circuit of the winding to the case, is manifested. All this indicates a malfunction of the interaction of parts during the operation of the generator. They can be identified by visual inspection of the mechanisms. This makes it easy to detect unwanted winding shorts, poor contacts and connections. Depending on the degree of the identified malfunctions, you can make a decision about the possibility of eliminating them yourself or contacting specialists for help.

Car generator voltage diagnostics

Most often, however, a voltmeter is sufficient. It must be connected to the terminals of the different poles of the battery and the car engine must be started.

After troubleshooting, a serviceable generator is mounted in the reverse order of its dismantling. The end action of this process is to carefully connect the ground.

After installing the generator, the voltage readings at the battery poles should be checked again. With the engine running at 3000 rpm, they should range from 13.5 to 14.5 volts. These values ​​mean that the generator has been restored to work and is in good working order.

Checking the voltage regulator

The next stage of diagnostics will be checking the voltage stabilization. To do this, turn on the car high-beam headlights and measure the voltage at the battery poles with a voltmeter. A deviation of values ​​not exceeding 0.4 volts from previous measurements when starting the engine indicates the serviceability of the generator. Deviations in the big direction indicate the unstable operation of the generator, the search for the causes of its malfunction will have to be continued.

Checking the car power supply circuits

Further search for the reasons for the loss of the generator's performance is to diagnose the car's power supply circuits. For this purpose, you will also need an electrical measuring device. With its help, you first need to check the diode bridge. In this case, a voltmeter is connected to the terminals of the generator and ground. Instrument readings exceeding 0.5 volts indicate a faulty diode. To determine their breakdown, connect a measuring device between terminal "30" and the disconnected connecting lead of the generator. An electrical current of less than 5 mA is acceptable.

Then the voltage regulator is checked. In this case, the engine should be warmed up for about a quarter of an hour at medium speed. In this case, all the lighting devices of the car must be turned on. This field is measured on the mass and terminal "30". The optimal performance of the device in this case may differ depending on the type and make of the car, which can be found out from its technical characteristics.

Also, the parameters of the regulated voltage depend on the modification of the car and its parameters, which can be measured by connecting the tester to the battery. Such a measurement is performed at maximum engine speed with all electrical appliances on the vehicle.

A multimeter is required when diagnosing a short to ground. To do this, put the tester in the "ringing" mode, touch the armature body with one probe, and the slip ring with the second. Everything is simple: if it does not ring, it is in good order; if it rings, it is defective.

Conclusion

Guided by these recommendations, diagnostics of an automobile generator can be carried out independently. To do this, you only need certain skills in using the simplest tools during dismantling and mounting, as well as using electrical measuring instruments. However, for a more accurate check and thorough diagnostics, you should contact certified car services, whose qualified specialists, using special equipment, will quickly identify and eliminate all malfunctions in the generator.

Video: how to check the generator

The main source of electricity in a car is the generator. It starts simultaneously with starting the engine, after which it generates energy and charges the battery. If it fails, the battery charge will not be enough for the long-term operation of the car, so the driver is obliged to monitor the condition of the generator.

There are a lot of problems due to which the generator can fail during operation. These can be both mechanical and electrical problems. A malfunctioning generator also manifests itself in various symptoms, among which the most common are:

• The appearance of extraneous sounds emanating from the generator;
• Battery problems: discharging, overcharging, boiling off electrolyte;
• Reducing the brightness of the headlights with increasing revs. This situation is considered normal if it occurs for a short time when switching to first gear from idle on a "cold" engine;
• Warning lamp signaling about the discharge of the battery while the car is moving;
• Electronics malfunctions, including dim headlights and weak beeps.

If the symptoms described above occur, the vehicle's alternator should be checked. Diagnostics, most often, is performed according to four parameters:

• Checking the recoil current strength;
• Diagnostics of the diode bridge operation;
• Checking the generator voltage regulator;
• Excitation winding check.

Depending on the identified problem during the diagnosis, the issue of the expediency of repairing the generator is resolved.

Generator Inspection Safety Rules

Before you start checking the car generator, you should familiarize yourself with the basic safety rules that will allow you to preserve the health of the diagnostician and not damage the unit. The basic rules for the safe inspection and repair of a generator are as follows:

Please note: If not only the generator is being checked, but also welding work on the car body, it is necessary to disconnect the generator and the battery completely from the vehicle's on-board network before starting them.

Checking the generator recoil current

For this check of the generator, you will need a multimeter equipped with a special probe to measure the current flowing in the wire. This probe looks like a clamp that wraps around a wire, and most often it comes with a diagnostic device. To check the generator recoil current strength it is necessary:

1. Put the clip on the wire that fits to the contact "B +" ("30") of the generator;
2. Next, start the engine and set high revs;
3. After that, one at a time, it is necessary to turn on the electrical consumers on the car - a radio tape recorder, air conditioning, steering wheel heating and others. When each consumer is turned on, readings from a multimeter should be recorded;
4. Next, you need to measure the recoil current when all consumers are turned on together (which were included in the previous test).

When all the measurements are obtained, it is necessary to compare the total indicator of the alternate switching on of consumers and the indicator of instantaneous switching on of all consumers. It is considered unacceptable if the indicator, upon instantaneous switching on of all consumers, is 5 or more Amperes less than the sum when switched on alternately.

Checking the diode bridge of the generator

To check the condition of the diode bridge of the generator, you must put the multimeter in the alternating current measurement mode. Connect one test lead of the diagnostic tool to the "B +" ("30") output, and the other to ground. The voltage with this connection of the probes should be no more than 0.5 volts. If the voltage is higher, the diodes are likely to be short-circuited.

You can also check the diodes for breakdown. To do this, disconnect the battery from the generator and also disconnect the wire that fits to the "B +" ("30") terminal. Next, the multimeter is connected between the disconnected generator wire and "B +" ("30"), after which readings are taken. If the discharge current of the multimeter shows more than 0.5 mA, there is a high probability of diode breakdown.

Checking the generator voltage regulator

To diagnose the condition of the car alternator regulator, you must use a voltmeter or multimeter in voltmeter mode. Before starting the measurements, you need to start the engine, turn on the headlights and let the engine run for 15-20 minutes. The measurement itself is carried out with probes, which are connected between the ground and the "B +" ("30") terminal of the diagnosed automobile generator. The obtained values ​​are recorded, after which they must be compared with the normal numbers for a specific car model. These figures can be found in the technical documentation of the machine. For most machines, the normal voltage ranges from 14 to 16 volts. If there are deviations from the standards set by the car manufacturer, there is a high probability of failure of the voltage regulator, in such a situation it will need to be replaced.

Excitation winding check

To check the serviceability of the excitation windings of the automobile generator, it is first necessary to remove the regulator and the brush holder in order to gain access to the slip rings. For diagnostics, an ohmmeter is required, the probes of which should be applied to the slip rings of the generator. As a result of the test, the resistance should be at a level of 5-10 ohms. You also need to make sure visually that there are no breaks in the winding.

To diagnose the short circuit of the excitation winding "to ground", you will need to connect one ohmmeter probe to any slip ring, and attach the second to the generator stator. As a result of the measurement, infinite resistance should be displayed on the screen.

When diagnosing the generator, it is also necessary to inspect it for mechanical damage. Based on the results of all checks, the expediency of repairing the device or replacing it with a new one is determined.

A generator test may be required when the battery charge indicator lamp on the instrument panel comes on, and this means that the battery charge has disappeared. It is useful for every driver to know how to check the generator and its parts, which will be described in detail in this article.

The lack of battery charge can occur not only through the fault of the generator, but for example due to the failure of the regulator relay. And before checking the generator, you should first make sure that the regulator relay is working properly.

How to check the serviceability of the relay of regulators of different types, I wrote in detail here in. And you can read about the generator device and its main malfunctions. The generator and the serviceability of some of its parts can be checked without disassembling the generator or with disassembly, and the verification methods will be described below.

If, during the check, some malfunctions of the generator are revealed, then they can be eliminated as described here in, about repairing the generator.

Checking the generator piece by piece.

Checking the stator generator. The generator stator is checked separately after the generator has been disassembled. All stator leads must be disconnected from the diodes (valves) of the rectifier unit.

First, visually make sure that the varnish insulation of the stator winding wires does not have traces of overheating (and even more so melting), which can occur during a short circuit in the rectifier valves. A stator with traces of melted insulation must be replaced.

Checking the generator using the stand .

Testing at the stand allows you to most accurately determine the serviceability of the generator and the compliance of its characteristics with the nominal ones. To assemble the stand, you will need to fix the electric motor with a pulley on a welded frame from a corner (or a shaped pipe), then fix the generator on the same frame so that the electric motor pulley rotates the generator pulley using a belt.

You will also need a rheostat 4 (see the connection diagram on the left) a voltmeter 3, a control 12-volt lamp (3 W) 1, an ammeter 5, a switch 6, and a car 7 (the generator itself is under the number 2 in the figure). Everything is connected according to the diagram in the figure.

Before checking the generator, the generator slip rings should be cleaned from plaque, and the brushes should be well ground in shape to the slip rings. After connecting all the components of the stand according to the figure, turn on the electric motor and with rheostat 4 set the voltage at the generator output to 13 volts. Then we bring the generator rotor speed to 5000 rpm.

At such speeds, we let the generator run for at least two minutes, then we measure the recoil current. A working generator of front-wheel drive vases (VAZ 2108 - 09) must have a current strength of at least 55 amperes. For more powerful generators of foreign cars, the recoil current is, of course, greater, and how many amperes exactly can be specified in the technical characteristics of a particular generator.

1 - generator, 2 - voltmeter, 3 - control lamp, 4 - rheostat, 5 - ammeter, 6 - switch, 7 - storage battery.

The walls for checking generators of foreign cars are practically the same, only the terminals of imported generators have different designations (D and B +), as in the figure just above.

If it turns out that the current is less than the prescribed one, then this indicates a malfunction in the stator or rotor winding of the generator, or damage to diodes, or wear of slip rings or brushes. In this case, disassembly and inspection of the windings and diodes will be required, as described above.

The generator output voltage check is checked at a rotor speed of 5000 rpm. In this case, the rheostat set the recoil current to 15 amperes and measure the voltage at the generator output. It should be 14.1 ± 0.5 volts, at a temperature of 25 ± 10 ° in the room where the stand is located.

If the voltage has a different value (less or more than 14.1 ± 0.5 volts), then replace the regulator relay with a new or known good one and repeat the test again. If replacing the relay does not help and the voltage still differs from the norm, then it is not a matter of the regulator relay, but of the stator or rotor windings, or in the faulty diodes of the rectifier unit.

Checking the generator using an electronic oscilloscope .

Not everyone has an electronic oscilloscope, but it allows you to quickly and accurately check the generator's health and determine the nature of the damage by the shape of the rectified voltage curve. Therefore, it makes sense to write such a way to test the generator.

To check, assemble the circuit as shown in the figure on the left. Then we disconnect the common output wire of the three additional diodes from the terminal B of the voltage regulator relay and wrap the tip of the disconnected wire with electrical tape (so that it does not short to the generator case).

Next, we connect the wire from the battery to terminal B (see figure) through the control lamp 1. Now the excitation winding will be powered only from the battery. We turn on the electric motor of the stand and achieve the generator rotor speed of about 1500 - 2000 rpm. Then, with the switch 6, we disconnect the battery from the generator terminal 30 and, using the rheostat 4, we achieve a recoil current of 10 amperes.

We check the voltage at terminal 30 of the generator with an oscilloscope. With serviceable rectifier diodes and serviceable stator winding, the rectified voltage curve has the shape of uniform saw teeth as in Figure A (see figure below).

A - the generator is working properly.
B - the diode is broken.
B - open circuit in the diode circuit or in the stator winding.

If there is an open or short circuit in the rectifier diodes or an open in the stator winding, then the shape of the curve will be with uneven teeth with deep cavities (see figure B and C).

When you have checked at terminal 30 and made sure that the shape of the curve is normal, you should check the voltage at plug 61 or at the tip of the wire that is disconnected from plug B of the regulator relay. These points are the common output of three additional diodes that feed the excitation winding when the generator is running.

And here, too, the shape of the stress curve must have the correct tooth shape. If the shape of the curve has an irregular shape of the teeth, then this indicates the failure of additional diodes.

You can read more about checking and restoring the generator and the regulator relay of a foreign car.

And finally, a few warnings that are important for every driver to know.

• The negative lead from the battery must always be connected to ground, and the positive lead must be connected to terminal 30 of the generator. Reverse (erroneous) connection of the battery will instantly cause an increased current through the diodes of the generator rectifier and the diodes will fail.
• Do not allow the generator to operate with the battery disconnected, as this will cause short-term overvoltages at terminal 30 of the generator and this will damage the voltage regulator relay and other electronic devices of the on-board network of a modern car.
• It is strictly forbidden to check the generator's serviceability for a spark, even by short-term connection of terminal 30 of the generator to ground. In this case, a large current flows through the diodes of the rectifier unit and they fail. You can only check the generator's performance using a voltmeter and ammeter.
• The diodes of the generator rectifier cannot be checked with a megohmmeter (it has a voltage too high for the diodes) or with a voltage of more than 12 volts. Since the diodes during such a check will be broken (a short circuit will occur).
• It is also forbidden to check the electrical wiring of the machine with a megohmmeter or a lamp powered by a voltage of more than 12 volts. If such wiring is necessary, then you must first disconnect the wires from the generator terminals.
• It is possible to check the insulation resistance of the generator stator winding with increased voltage only on the stand, but always with the phase winding leads disconnected from the rectifier.
• When bodywork using electric welding, be sure to disconnect the wires from all terminals of the generator and battery.

That seems to be all. Of course, checking the generator is not such a simple matter, but with a competent approach and the availability of appropriate knowledge, it is quite possible to identify any malfunction and fix it without the help of an auto electrician, success to everyone.

First, remove the positive «+» terminal from the battery in order to avoid accidental short circuit, then disconnect all contacts from the generator and, by bending the latches, remove its back cover (the design of which provides for this). Thus, we can carry out a general check of the diode bridge and stator winding, as well as the rotor. To check the voltage regulator, you must remove his from the car generator.

Fig. 2

Fig. 3

1. First, we check the generator for a short circuit to ground.

Press positive «+» multimeter probe to terminal "thirty" generator, and negative«-» probe to its body. In good condition, the diode bridge does not pass current in this direction, there is no sound signal, and the lamp does not light up.

2. We check the positive diodes for "breakdown".

Positive «+» press the multimeter probe to the terminal "thirty" generator negative «-» to the terminals of the winding and diodes (generators of type 9412.3701, where the bolts are isolated from the terminals with textolite washers and are closed to "Mass" ), or one of the axle mounting bolts (generators of type 37.3701, where the bolts are connected to the terminals, but isolated from"masses" - Fig. 5).

If the diodes are in good order, then the resistance tends to infinity, and the light does not light up. If even one of them is "broken", then the light comes on, hearth multimeter There is a beep.

3. Check the negative diodes for "breakdown".

To do this, we press the positive «+» multimeter probe to the terminals of the winding and diodes 37.3701 - Fig. 5). Negative «-» press against the generator body.

4. Check additional diodes for "breakdown".

Press positive «+» multimeter probe to input "61" generator. Negative «-» probe to the terminals of the winding and diodes (generators of type 9412.3701), or to the axle mounting bolts (generators of type 37.3701 - Fig. 5). If the resistance tends to infinity and there is no sound signal, the lamp does not light - the additional diodes are operational. When the polarity is reversed, they must pass current.

To determine an open circuit in the diode, you will also have to .

It is worth noting that testing diodes with a multimeter and, to a lesser extent, a light bulb, in which diodes are tested under load, are not 100% effective. For this, there are more accurate instruments such as an oscilloscope.

If the diode bridge is working properly, then proceed to check the stator winding.
5. Check the stator winding for open circuit.

We alternately connect the multimeter probes between all three terminals of the stator winding.

A sound signal or a lit lamp in all three cases tells us about the integrity of the winding.

6. We check the short circuit of the stator winding to ground.

We connect the probe to one of the winding terminals, and the other to the generator case. If the resistance tends to infinity, there is no sound signal, the lamp does not light - there is no short circuit.

7. We check the stator winding for interturn short circuit.

To do this, we transfer the multimeter to the resistance measurement mode "200 Ohm" and connect the probes between all three terminals of the stator winding. The resistance should be 0.2-1.2 ohms and be the same across all three pins.