How to check the mass on the generator. How to check a car generator with your own hands. Checking the rotor winding

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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 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 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 carried out using a voltmeter or ammeter.
  • Valves are checked 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 section and length.
  • Before checking the device, make sure that all connections are working and that the tension is correct. drive belt... A belt is considered to be correctly tensioned, which, when pressed into 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

  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 about 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. You can also check the regulated voltage by connecting a voltmeter to the terminals. It should be noted that this measurement will be inaccurate if you are confident that the wiring is 100% good. In this case, the motor must operate at medium speeds close with the headlights on and other consumers of electricity. 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 AC 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 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 a clamp that grips 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 turned 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 downwards is allowed.

Checking the generator excitation current

  1. To check the excitation current of the generator, start the motor and run it high.
  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.

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 coming from the generator;
  • Battery problems: discharging, overcharging, boiling off the electrolyte;
  • Decrease in 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 the mode idle move 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 generator check, 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, you need to:

  1. Put the clamp on the wire that fits 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 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, when all consumers are instantly turned on, is 5 or more Amperes less than the sum when turned 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 goes 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 generator 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 technical documentation cars. For most cars 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.


Self-checking the motor armature can easily be done at home. This will allow, firstly, to independently restore the working capacity of the tool, and secondly, not to overpay to a specialist for a fairly simple operation. All you need to check is a screwdriver and a multimeter. Additionally, you can purchase a special device for determining the turn-to-turn closure.

Step 1. Visual inspection of the tool

Very often there are situations when the tool is still working, but not as it should be. And in 30% of cases, a burnt anchor is to blame. This can be revealed visually, even before opening the case.
Indirect signs of a "tired" electric motor armature are the following malfunctions:
  • When the motor is running, very strong sparking is seen on the manifold.
  • When you try to start a grinder (drill, circular saw, etc.), there is a severe voltage drop (lighting blinks).
  • The start of the electric motor is accompanied by sharp jerks.
  • A characteristic smell of burnt wiring comes from the hull.
  • The tool does not pick up the same power.
Please note that more than half of these signs may also indicate trivial wear of the electric motor brushes. If they are worn out or crumbled, then the anchor, most likely, has nothing to do with it. We change to new ones, clean the collector from graphite deposits, and calmly work on. If the brushes look intact, and the above symptoms are observed, with an 80 percent probability it can be argued that the problem is in the motor armature.
If the power tool does not show signs of life at all, there can be many more reasons, and more than just checking the anchor will be needed.

Step 2. Dismantling the power tool

One way or another, if everything is in order with the brushes, you cannot do without disassembling the tool. At this stage, the most important thing is not to harm even more. Special attention should be paid to correct selection screwdrivers, since it will be problematic to unscrew the damaged screws, and the check will turn into painful plumbing work. Some tools use different lengths of fasteners. Their location needs to be remembered (it is better to write down or sketch).
In order to successfully assemble the power tool after diagnostics and repairs, beginners are advised to photograph each stage of disassembly. This will help a lot if you forget which part was as it stood before the check.

Stage 3. Preparing the motor armature for testing

After the anchor has been removed from the case, it is advisable to prepare it for diagnostics. The procedure consists in thoroughly cleaning the collector lamellas from graphite deposits. If this is not done, further verification may not give the desired result.
You can remove plaque with rags and alcohol. If there is not a deposit on the lamellas, but a thick layer of carbon, it will have to be removed with fine-grained sandpaper. Make sure that there are no visible abrasive grooves on the manifold. This will worsen the contact of the lamellas with the brushes, as well as accelerate their wear.


Step 4. Visual inspection of the anchor before checking

You need to look at the following:
  • Collector lamellas. They should not be heavily worn.
  • Motor armature winding. We are looking for breaks or visible traces of wire burning.
  • Contacts. The entire winding is soldered to the collector lamellas. These points need to be checked for integrity.
If the collector is too deep, the armature must be replaced. Burn marks on the windings or contacts indicate that the part is defective. You can rewind, of course, but this is a thankless job and requires special skills. It's easier to buy a new one.

Step 5. Checking the armature with a multimeter

Checking the motor armature with a multimeter consists of two stages. First of all, you need to ring him for a breakdown. For this, the multimeter is set to the circuit test mode with a sound signal.


Next, we go through the collector lamels with one probe, and with the second along the armature body.


The second stage of checking the armature with a multimeter is to measure the resistance between adjacent windings. To do this, the device is set to the resistance determination mode at the lowest threshold (as a rule, it is 200 Ohm).


Further, the probes are applied to the adjacent collector lamellas, and the readings on the screen are recorded. When measuring the resistance between all adjacent lamellas, there must be the same value. If this is not the case, the anchor is faulty.


The same is indicated by the complete absence of resistance on any of the windings.

Stage 6. Checking the armature for turn-to-turn closure

Before you check the motor armature for an interturn short circuit, you need to get a special device. It costs a penny, and there is a lot of information about it on the Internet.
The essence of checking the anchor is to apply this very device to all sections of the body. According to the indications of the LED indicator, a malfunction is determined.

Step 7. Replacing the armature and reassembling the tool

The defective anchor is either rewound or replaced with a new one. Fortunately, today even the cheapest Chinese instrument can be found in online stores with suitable accessories. Before installing a new or restored anchor, it is advisable to check the algorithm described above.
If everything is normal, we put everything back and work. When changing the armature of the electric motor, it is also recommended to install new brushes. Fortunately, they are penny.

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.


The content of the article:

Various signs and symptoms can indicate reduced performance and generator failure. The main ones are the appearance of noises of a different nature, emanating from the generator, insufficient battery charge or its complete discharge. If the battery is insufficiently charged, the car either cannot be started, or after a while its engine may stall. It may also indicate that the battery has reached the end of its useful life.

Signs of mechanical damage to the generator


The presence of mechanical damage to the generator can be recognized by the nature of the sounds it makes during operation. It can be squeaks, whistles, bouncing, howling, knocking. Most often the problem in this case is wear or insufficient lubrication of the bearings. If suspicious noises persist after relubrication, a complete bearing replacement may be required.

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. You can identify them by visual inspection 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


Causes malfunctioning the generator can consist not only of mechanical damage to its parts. To detect them, you should also check the indicators of its output voltage. For this purpose, it is necessary to use electrical measuring instruments. Sometimes ohmmeters or multifunction testers - multimeters are used for this.

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.


The voltage at the battery terminals when starting the engine must not be less than 8 volts. In this case, the measurement accuracy will be higher if they are carried out in an environment with a temperature of +20 C and an already warmed up car engine.
After fixing the indicators when starting the engine, you should gradually increase its speed to 3000 per minute. When such a load is reached, the voltmeter readings must be taken into account again. Fixing measurements of less than 12.5 volts will indicate a malfunction of the generator and the need to repair it.


The faulty generator must be dismantled by first disconnecting it from the battery terminals. Then you should unscrew the fastening of the voltage regulator with a screwdriver. After that, carefully inspect and determine the degree of wear of the generator brushes, as well as its slip rings, and clean them in case of carbon deposits. Often the reason for the loss of generator performance is a malfunction of the voltage regulator. Therefore, it must be periodically checked and replaced if any problems are found.

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 working properly.

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 using 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 upward indicate unstable work generator, the search for the causes of its malfunction will have to continue.

Checking the car power supply circuits

Further search for the reasons for the loss of generator performance is to diagnose the vehicle'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.


The serviceability of the field winding is checked by measuring its resistance. To do this, you can use a multimeter or ohmmeter. At the beginning of such an operation, the voltage regulator and the brush holder are removed. The winding and its integrity are visually inspected, if necessary, slip rings are cleaned. The meter is connected to the rings. The optimal resistance of serviceable parts should be between 5 and 10 ohms.

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, it is quite possible to carry out diagnostics of a car generator 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 with the help of special equipment will quickly identify and eliminate all malfunctions in the generator.

Video: how to check the generator

Content:

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

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

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

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

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

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

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

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

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

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

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

How to check the generator voltage regulator with a multimeter

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

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

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

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

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

The verification procedure takes place in several stages:

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

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

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

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

How to check the generator rotor with a multimeter

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

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

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

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

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

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

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