The generator is quite stable in operation. Its failure, as a rule, occurs due to environmental factors, for example, in the form of condensing moisture on contacts and metal, causing corrosion and breakdowns, as well as as a result of mechanical wear of rotating parts.
To know how to check the charging of a generator, you need certain basic knowledge about the structure of the unit, its components and the principle diagram of the operation of some of its parts.
To measure electrical resistance, you will need a special testing and measuring device: the so-called multimeter or ohmmeter.
Before checking the generator winding with a tester, it is necessary, first of all, to inspect it for the presence of external damage to the insulation, burns in the winding resulting from short circuits. If visible damage is detected, 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 terminals must not contact each other.
Need to check:
- no winding circuit break
- absence of short circuit of the windings with the housing.
We set the ohmmeter to test and measure the resistance.
In the first case, the ohmmeter tips are connected in turn to each of the three winding terminals. If the winding is faulty, the control device will show infinite resistance (i.e. one in the left digit of a digital multimeter and a maximum deviation to the right if the multimeter is analog).
In the second case, the ohmmeter tips are connected to the winding terminal and to the stator housing. If there is a short circuit, the test device should show low resistance.
A serviceable stator, therefore, in these two tests should show low resistance in the first case and infinitely high resistance in the second.
Checking the serviceability of the voltage regulator in the generator
Before checking the generator voltage regulator, it must be removed 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 brushes protrude less than 4.5 mm, the voltage regulator needs to be replaced.
The voltage regulator itself is checked using additional power sources: 12-14 V and 16-22 V.
Accordingly, the first source can be a battery, the second source can be a battery with 1.5-volt batteries connected in series to it.
We connect the positive output of the battery to the output of the device, the negative one 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 the light should be on;
- 16-22 V the light 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 functionality
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, and then closing its contacts with an iron object insulated from the hands. If the capacitor is in good condition, i.e. with its ability to charge and retain a charge, a spark should appear.
Before that, it is necessary to clarify that they can be 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 install a control device to ring and measure 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 increase until it begins to approach infinity. These are the results for a working capacitor.
To arrange channels for wiring and pipelines, a wall chaser is used. This tool does not necessarily need to be purchased ready-made in a store. It will be much more economical to make it from a grinder and other available elements.
It will be useful for any radio amateur and electrician to know the different characteristics of small parts and other electrical equipment. For example, you can read about the principles of operation of a power regulator on a triac, but it reveals the features of color marking of resistors.
A non-working capacitor will:
- cause the ohmmeter to squeak and show zero resistance;
- immediately show infinite resistance.
Non-polar capacitor test.
We set the megaohm values on the control device and touch it with the contacts of the capacitor terminals. At low resistance values (less than 2 mOhm), the capacitor is most likely inoperative.
Checking the generator diode bridge with a multimeter
The task of rectifier diodes is to correctly pass current in the direction from the generator and block its passage in the opposite direction. Any deviation in its operation is considered a malfunction of the diode bridge. Let's take a closer look at how to check the diode bridge of a generator.
First you need to remove the diode bridge from the generator and disassemble it to gain access to the diode contacts. The soldered leads on the stator need to be unsoldered.The multimeter switch should 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 circuit diagram.
Checking power diodes.
The negative contact of the multimeter is connected to the diode bridge plate, the positive contact is connected to the diode terminal. The current must pass. The device readings should tend to infinity. We connect the positive probe of the multimeter to the diode bridge plate, the negative probe to the diode terminal. The multimeter should show a resistance of 400 to 800 ohms.
Checking auxiliary diodes.
We connect the negative output of the multimeter to the auxiliary diode plate, and the positive output to the diode output. The multimeter should show a value between 400 and 800 ohms. We connect the positive contact of the multimeter to the auxiliary diode plate, the negative contact to the diode terminal. The device readings will tend to infinite resistance.
Bearing Inspection
A bearing is a mechanical part whose failure involves a change in its physical properties. This could be corrosion, cracks, wear, damage, play, or difficulty rotating. An outward sign of a problem with the generator bearing is the hum and noise produced by the generator.
In this case, the rear bearing is removed and examined for the above-mentioned part defects. The bearing ring should rotate freely without creating any extraneous noise.
If we talk about a car generator, its front bearing is usually mounted in the cover. The check is carried out according to a similar principle, rotating the lid and holding the center. The bearing should not jam or make noise.
A bearing with poor rotation or deviation along the axis of rotation must be replaced.Thus, checking the generator for functionality is not very difficult. The main thing is to understand the essence of the processes occurring 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 fault in the generator.
Let's see how to check the generator with a multimeter in the video
Sometimes a car enthusiast is faced with the question of checking his car’s generator. After all, it is very important to promptly prevent and eliminate possible operational irregularities that could lead to battery failure and problems with starting the engine. The ideal option would be to entrust this matter to a specialist, but if this is not possible, you can check the generator also, the main thing is to have a multimeter available.
How to check the generator without removing it from the car
In this case, you can check the generator and. It is necessary to connect a multimeter to the battery and measure the voltage in various modes with the engine running. To do this, you need to give an electrical load: turn on/off the headlights, press the gas pedal, turn on the stove, and so on. If, by experimenting in this way, you can notice that the voltage remains within 14-14.2 Volts, then we can safely say that everything is in order with the generator and charging relay. If jumps of more than 0.5-1 Volt are observed, there are malfunctions.
How else can you test the generator?
First, check the belt tension: sometimes it's all about loosening it. Having disassembled the generator under conditions, it is worth checking the rotor. To do this, you need to find out what the resistance is between the stator slip rings. If these indicators do not exceed 5-10 Ohms, then everything is in order, if this figure is higher, there may be a break in the windings somewhere. Next, using a multimeter, you need to check the breakdown of each ring for ground. If there is resistance between the rotor and each ring, then there is no need to talk about a breakdown; if there is none, then there is a breakdown. With such a breakdown, it is impossible to repair the generator at home.
It's easy to check the diode bridge. As you know, it consists of 6 - three positive and three negative. You need to disconnect all the leads from the plates with diodes and carry out a test: attach the probes to the diode leads, and then repeat the experiment, swapping them. In one position the beep should be heard, but not in the other. If a squeak is heard in both directions, it means a broken diode, which means it will have to be replaced. But without sufficient experience it is difficult to do this, so you will have to change the entire diode plate.
The stator must be carefully inspected - there should be no burns or damage to the winding. Afterwards you need to test the winding with a multimeter. As for the bearings, nothing should interfere with their free rotation: there should be no noise or play. Brushes should extend beyond the edges by only 5 mm. Chips, jams and play are excluded. If there are any deviations, it is better to replace it.
A car generator is one of the most important components in a car. It is responsible for the supply of energy, is a backup source, and takes on huge loads in the event of a network failure, because you can’t go far on battery alone. A caring motorist is obliged to periodically check the operation of the generator and monitor its condition. From the article you will learn how to check the generator using a light bulb and other methods.
Lamp test
ATTENTION! A completely simple way to reduce fuel consumption has been found! Don't believe me? An auto mechanic with 15 years of experience also didn’t believe it until he tried it. And now he saves 35,000 rubles a year on gasoline!
A lamp test is testing a generator using a “fog light”. The diagnostic task is to determine whether the generator rotates correctly when exposed to drill speeds. In this case, the light bulb plays the role of an indicator - if the generator rotates normally, then it (the light bulb) should light up.
It is important to know that a working generator should produce a voltage within 14.1-14.5 V. And at the same time, the voltage should not jump or have differences. In other words, the voltage must be stable.
To carry out this type of testing, the autogenerator will have to be removed from the car and the following steps must be taken:
- clamp it in a vice so that it is convenient to work;
- integrate a battery with the generator.
We also advise you to find out the type of generator before diagnosing. As you know, they are different in terms of connection. This means that the units may have a different number of contacts. There are 2-pin, 3-pin or 4-pin generators.
4-block generators contain the following contacts:
- a plus of a constant type, marked by the Latin S;
- plus associated with ZZ - IG;
- contact for control unit marked M;
- for the warning lamp – L.
We continue with a series of actions:
- a positive cable is run from the battery to both “+” dynamos;
- a lamp with a value of 50 W is integrated to the desired contact;
- voltage is applied to the lamp;
- the generator is rotated using a drill;
- The indicator light is tested.
So, if the light is bright and the voltage on the dynamo is within normal limits, then the generator is fully operational. In any case, it is capable of recharging the battery.
The connection between the generator and the battery is an important tandem. Under no circumstances should you disconnect the battery while the engine is running! Ask why? This unnecessarily loads the voltage stabilizer and generator, which causes a failure in the overall system. This can even be seen from the indicator: if the lamp under test is disconnected from the battery, then if the dynamo is working, it will continue to glow, but the voltage will no longer be stable.
The battery should also not be disconnected due to a simple short circuit. A short circuit will burn not only the unit itself, but also the electronic units installed in the car.
So, the rule not to remove the terminals from the battery under any circumstances must be included in the list of the main canons of the motorist. Those who like to “light” the battery do the wrong thing, which often happens in the winter season. Keep a charger in your car and don't push your luck. Once or twice you'll be lucky, but on the third you can burn down the entire electrical system.
Checking the unit in parts
The generator is essentially tested legally piece by piece. For example, most experts agree that the light bulb test is only 95% accurate in diagnosis. And indeed, this is so.
In order to fully check the generator, it is necessary to diagnose the unit in parts.
First, the stator is checked. It is tested individually once the generator is disassembled. The stator is separated from all “native” resistors and semiconductor devices so that its testing gives accurate results.
Diagnosis is carried out as follows:
- The insulation of the winding wiring is inspected, which should not have signs of overheating or melting (which is much worse, since it indicates a short circuit). If traces of overheating are found on the part, the stator is replaced with a new one.
- Next, take a multimeter, which is set to ohmmeter measurement mode. The generator is checked for breaks in the windings or short circuits.
- Resistance is tested. To do this, you need to connect the probes, adhering to the scheme of alternate connection to the ends. The impedance between them should be two to three tenths of an ohm.
- A multimeter is used to test whether the electrical winding is shorted to the housing. To do this, one of the probes of the device is connected to the stator housing, and the other to each of the winding terminals. It shorts out if the multimeter makes a sound in buzzer mode. Again the stator is to blame, which has to be replaced.
It often happens that the cause of a short circuit is in the winding wires. Any of the wires may be slightly exposed and touching this part of the housing. The problem can be solved simply - this part of the wire is bent and covered with insulating varnish. However, in most cases, it is more difficult to determine a winding short circuit, since the problem area is not visually visible.
The next part of the generator that is checked is the rotor. Its electrical winding PP is being tested. It can be easily diagnosed even with the generator not removed. It will be enough to dismantle only the relay-regulator with the brush block, and then connect the test device to the copper contacts. However, for the most part, specialists test the rotor independently of the generator.
As in the case of the stator, the probes of the meter, set to Ohm measurement mode, are connected to the rotor contacts. The normal ohmmeter value should be within 2.5-5 Ohms if the generator model has a power of 500-1200 W.
With smaller or larger values, a diagnosis is made: either an interturn short circuit or a poor connection of the winding leads to the contacts.
Attention. If the device shows zero resistance at all, there is definitely a break in the rotor winding.
Device of semiconductor diodes (VB)
The VB or diode bridge is also checked without fail. A good diode, as you know, must pass a limited voltage, that is, along one line. As for the faulty diode, it does not react to electrical voltage in any way or does so on both lines, which leads to a short circuit.
The entire diode bridge is replaced, as a rule, if at least one of the diodes fails. The fact is that they (diodes) are pressed into a plate. It can be very difficult to remove and change one of the diodes, so you have to change the entire unit.
- the presence of a short circuit in the diode bridge can be determined without removing the generator from the car;
- Before checking, it is recommended to disconnect the generator wiring and disconnect the battery terminals;
- testing can be carried out not only with an ohmmeter, but also with a test lamp;
- three VB diodes are called positive, since they are connected to the “+” of the rectified voltage, and the other 3 are negative, since they have a “-” on the body (both 3-diode groups are pressed into a separate soft metal track, integrated either with ground or with the 30th current output of the generator).
So, the check is carried out as follows:
- First, the presence of a short circuit in the positive 3-diode group is tested. To carry out this operation, positive voltage is passed from the battery through the light bulb to the generator terminal number 30. The negative terminal of the battery is connected to the generator core. In such a circuit, if the indicator (light bulb) lights up, it means that there is a short circuit in the group.
- The presence of a short circuit in the group of negative diodes will also be indicated by the glow of the light bulb. However, the connection diagram is slightly different. From the battery, the positive cable is connected to one of the generator retaining screws. An indicator light is embedded in the wire. The negative from the battery also goes to the body.
The glow of the indicator may also indicate problems with the stator, but most often it indicates a short circuit in the diodes.
Punching in resistors can also be detected using a measuring device. It must be an oscilloscope. It is also possible to check for a short circuit on the stand - problems in this case will be indicated by a decrease in the output voltage by 20-30 percent.
And, of course, you can test the breakdown in a diode bridge using a multimeter set to ohmmeter mode. One of the terminals of the device is connected to the positive or negative plate (positive or negative group), while the other alternately touches the diode terminals. Then the probes are swapped.
The problem can be judged if there is no continuity (in other words, if the multimeter shows resistance in both directions). Also, the zero resistance of the multimeter indicates that the diodes are broken.
Attention. As a rule, if one diode of a group is broken, the battery constantly shows undercharging.
Additional diodes
Checking the additional diodes is also the most important part of testing the generator in parts. They (additional diodes) are installed on all modern cars, including the new domestic VAZ.
To test the short circuit on additional diodes, it is not at all necessary to dismantle the entire unit. It’s just important not to forget to remove the terminals from the battery and disconnect the wiring before checking.
So, the connection is made as in the diagram above. The plus from the battery goes to the 61 output of the generator, and in the middle there is a 1 or 3-watt indicator light (number 2 in the diagram). The negative wire goes to one of the generator mounting bolts.
A short circuit is indicated by the glow of the light bulb. If it lights up, then a short circuit is observed in one of the additional diodes.
The test can be carried out without removing and disassembling the generator, however, in order to determine which resistor has failed, you should dismantle the rectifier and test each of the components separately using a measuring device.
Additional resistors can also be tested using various meters. For example, it could be a voltmeter. If the voltage on it shows less than 14 V, this is an obvious breakdown.
battery
Checking the generator, in most cases, is caused by the Control Ind lighting up on the dashboard. However, this does not at all prove that the generator is faulty. An indicator light on the dashboard may indicate a battery failure.
Why does the battery lose charge? Isn't this a consequence of the generator output? Certainly not. This may be caused, for example, by damage to the regulatory relay.
We learned that the generator can be competently tested not only with a light bulb, but also in other ways. It is best to check the unit separately, because it is this kind of diagnostics that gives a complete result.
The generator is the main source of current that powers the vehicle's electrical appliances. A malfunction of a car generator entails insufficient charging of the battery, which leads to a voltage drop, blackout and a complete stop of electrical appliances. For this reason, it is necessary to regularly check the serviceability of the generator and immediately respond to problems in its operation.
The content of the article:
Various signs and symptoms may indicate decreased performance and failure of the generator. The main ones are the appearance of noise of a different nature emanating from the generator, insufficient battery charge or its complete discharge. If the battery is not sufficiently charged, the car either cannot be started, or the engine may stall after some time of operation. This 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 determined by the nature of the sounds it makes during operation. It can be creaks, whistles, rattling, howling, knocking. More often the problem in this case is wear or insufficient lubrication of the bearings. If the suspicious noises do not disappear after changing the lubricant, the bearings may need to be completely replaced.
The presence of extraneous noise can also be a consequence of an interturn short circuit in the stator winding. In a similar way, a malfunction of connections and contacts, a short circuit of the winding to the housing, manifests itself. All this indicates problems with the interaction of parts during generator operation. They can be identified by visual inspection of the mechanisms. At the same time, it is easy to detect unwanted winding short circuits, bad contacts and connections. Depending on the extent of the detected malfunctions, you can decide whether to fix them yourself or seek help from specialists.
Car generator voltage diagnostics
The reasons for the malfunction of the generator may lie not only in mechanical damage to its parts. To detect them, you should also check its output voltage. For this purpose, it is necessary to use electrical measuring instruments. Sometimes ohmmeters or multifunctional testers - multimeters - are used for this.
However, most often it is enough to use a voltmeter. It must be connected to the terminals of different poles of the battery and the car engine must be started.
The voltage at the battery terminals when starting the engine should not be less than 8 Volts. At the same time, the accuracy of measurements will be higher if they are carried out in an environment with a temperature of +20 C and a car engine that is already warmed up.
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. Recording measurements of less than 12.5 Volts will indicate a malfunction of the generator and the need for its repair.
The faulty generator must be dismantled by first disconnecting it from the battery terminals. Then you should unscrew the voltage regulator fastenings with a screwdriver. After this, carefully inspect and determine the degree of wear of the generator brushes, as well as its slip rings, and clean them if there is carbon deposits. Often the cause of generator failure is a faulty voltage regulator. Therefore, it must be periodically checked and changed if problems are detected.
After troubleshooting, a working generator is mounted in the reverse order of its dismantling. The final step of this process should be to carefully connect the ground.
After installing the generator, you should again check the voltage readings at the battery poles. When the engine is running at 3000 rpm, they should vary from 13.5 to 14.5 volts. These values mean that the generator's functionality has been restored and it is in good working order.
Checking the voltage regulator
The next diagnostic stage will be checking voltage stabilization. To do this, turn on the car's high-beam headlights and use a voltmeter to measure the voltage at the battery poles. A deviation of values not exceeding 0.4 Volts from previous measurements when starting the engine indicates the serviceability of the generator. Deviations towards the larger side indicate unstable operation of the generator; the search for the causes of its malfunction will have to be continued.
Checking the vehicle's power supply circuits
Further search for the reasons for the loss of functionality of the generator consists of diagnosing 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, the voltmeter is connected to the generator and ground terminals. Device values exceeding 0.5 Volts indicate a malfunction of the diodes. To determine their breakdown, you should connect a measuring device between terminal “30” and the disconnected connecting wire of the generator. An acceptable electric current strength of less than 5 mA is acceptable.
Then the voltage regulator is checked. The engine should be warmed up for about a quarter of an hour at medium speed. In this case, all vehicle lights must be turned on. The field of this is measured at ground 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 regulated voltage indicators depend on the modification of the car and its parameters, which can be measured by connecting the tester to the battery. This measurement is carried out at maximum engine speed with all electrical appliances of the car turned on.
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 this operation, the voltage regulator and brush holder are removed. The winding and its integrity are visually inspected, and if necessary, the slip rings are cleaned. The meter is connected to the rings. The optimal resistance of working parts should be from 5 to 10 ohms.
A multimeter is necessary 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 contact ring with the second. It's simple: if it doesn't ring, it's working, if it rings, it's faulty.
Conclusion
Guided by these recommendations, you can easily diagnose a car generator yourself. To do this, you will only need certain skills in using the simplest tools for dismantling and assembling, 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 problems with the generator.
Video: how to check the generator
A car generator may fail for the following reasons:
- wear of the excitation coil rotor bushings;
- voltage regulator malfunction;
- breakdown of rectifier bridge diodes;
- short circuit or breakage of windings;
- collector zone malfunction.
Most of these faults can be diagnosed without removing the generator from the car, since this work in some cars requires special tools, access from the bottom, and complex plumbing operations.
Diagnosing wear on excitation coil rotor bushings
Wear of the rotor (armature) bushings of the excitation coil leads to an increase in sliding friction, and as a result, overheating of the generator, a decrease in the efficiency of converting mechanical energy into electrical energy, and an increase in the load on the car engine.
Video - how to check battery charging from a generator:
In the most critical case, the bushing may break and the rotor may jam. This can cause the alternator belt to break, which in turn can lead to serious engine problems.
That is why timely prevention of the generator begins with the bushings. Sometimes bearings are used instead, although bushings are more reliable.
Bushing wear is usually diagnosed by a characteristic metallic ringing sound when the generator is running and an increase in the stretch of the generator belt.
It’s easier to remove the belt and check the runout of the generator pulley by hand, moving it perpendicular to the axis. The presence of even slight play indicates the need to replace bushings or bearings.
Voltage regulator malfunction
The voltage regulator ensures a constant voltage level at the generator terminals at different engine speeds. If you look at a typical generator circuit, the voltage regulator controls the field coil current.
The generator is a self-regulating system. If the speed increases, the voltage on the regulator increases, it reduces the current flowing through the field coil. According to the law of induction, the voltage on the stator coils decreases, and therefore the voltage at the generator output decreases.
Video - how to check the generator on a car without removing it:
During normal operation, the generator provides a stable voltage to the battery with the engine running, ranging from 13.3 to 14.5 Volts, regardless of engine speed.
An excess, as well as a lower voltage level, indicates a possible malfunction of the regulator; it must be checked.
Structurally, the regulator can be made in the form of a block with brushes or without them.
Sometimes it is called a “pill” or “chocolate”.
In most cases, it can be easily dismantled without removing the generator and tested at home or in the garage. A typical voltage regulator test circuit is shown in the figure.
As lamp 6, you can use any interior light bulb. 1 – battery, 2 – relay regulator, 3 – electronic unit, 5 – terminal for connecting a thin wire going to the generator. If the lamp lights up, then the regulator is working. But if the battery charge voltage is more than 15 Volts, the voltage regulator still needs to be changed.
Video - checking the generator on a car with a multimeter:
It is also necessary to change the regulator if the brushes are very worn. However, if you have some experience in repairing power tools, you can try changing the worn brush (preferably both brushes at once).
In almost half of the cases, generator malfunction is caused by a failure of the voltage regulator.
Breakdown of rectifier bridge diodes
This is perhaps the most dangerous and difficult to fix malfunction. Very often it occurs when the battery polarity is reversed. This is when the battery terminals are connected in reverse polarity. In this case, several more fuses and units of the car may burn out.
Video - checking the generator at home:
Typically, diodes fail in pairs, since the breakdown of one leads to the supply of forward voltage to the series diode. When the diode breaks down, its resistance becomes almost zero.
In this case, the generator begins to overheat, increasing the load on the battery. A breakdown of the diode bridge can cause a short circuit in the electrical wiring and a fire..
If you notice a burning smell coming from the generator area or the generator is getting excessively hot, immediately disconnect all wires going to the generator, especially the thick wire. Carefully isolate them and proceed to the parking area.
Video - how to check the diode bridge on a car generator:
It’s easy to check the breakdown of the rectifier bridge diodes. The generator should “ring through” like a diode. To do this, switch the multimeter to the “Diode” position. Then disconnect all terminals from the generator. First, connect the multimeter probes between the thick wire terminal and the vehicle ground in one direction, then the opposite direction. It should “ring” in one direction (resistance from 200 to 1000 Ohms, like diodes in direct connection), but not in the opposite direction (resistance is very high, more than a hundred kiloOhms).
Of course, it is better to remove the generator, disassemble it, dismantle the diode bridge and test each diode individually.
Sometimes diode bridges of generators are called “horseshoe”, it is clear why. The round ones (6 pieces) are power diodes; they usually burn out and are difficult to change. When installing them, welding is not used. At worst, you can simply bite out a faulty pair of them without replacing them. The generator will still work, although not at full capacity. Cylindrical diodes serve the voltage regulator. They fail less often, but they also need to be checked as described above.
Short circuit or broken windings
If a winding break can still be somehow detected using a multimeter, and then by disassembling the generator, then a short circuit is poorly diagnosed, since the resistance of the windings is low.
Video - how to check whether the generator is working on a car without removing it:
The main sign of a malfunction in the generator windings is a change in the color of the varnish insulation of the copper conductors of the generator winding. With increased short circuit currents, the color of the wires becomes much darker. This is accompanied by a burning smell when operating the generator.
You can send the generator for rewinding, but this is now expensive. If it is possible to buy a similar one or with the same fitting dimensions from another car, it is better not to rewind.
Changes in the color of the windings can be detected visually. The generator has many technological holes for cooling; in good lighting, you can examine the color of the windings.
Collector zone fault
The commutator is the brass cylindrical contacts of the exciting winding along which the brushes move
They usually wear unevenly. This leads to sparking in the brush area, overheating of the commutator, and even greater wear of the brushes and commutator.
During generator maintenance, the collectors are bored and ground. This cannot be done endlessly, so after several repairs the collectors are replaced.
Video - quick check of the generator without installing it on the car:
You can diagnose collector wear when the generator is disassembled. If you remove the voltage regulator with brushes, you can feel the commutator area with your finger. If she is “humpbacked,” you should think about prevention.
You can detect sparking brushes when the engine is running, which is evidence of commutator wear, at night by turning off all lighting fixtures.
The generator is one of the most conservative components of a car. Its design has remained virtually unchanged for more than fifty years. If you carry out routine maintenance on time (cleaning, replacing bearings or bushings, belts, brushes), it will last a long time.
Video - how to ring a generator with a multimeter:
May be of interest:
Scanner for self-diagnosis of a car
How to quickly get rid of scratches on a car body
What are the benefits of installing autobuffers?
Mirror DVR Car DVRs Mirror
Similar articles
Comments on the article:
Alexander
I usually check the generator in the fall, before the cold weather. This takes a little time, but saves you from additional expenses for buying a new one or repairing it. Lubricate and wipe the collector on time. As practice shows, it is true that most often either the regulator or the diode bridge fails, but in this case not everyone can cope with such a problem on their own.
Valentine
The rectifier bridge, consisting of diodes and a regulator, gets quite hot during operation, and its cooling is very weak due to its design features (located at the rear of the generator).
When driving into a deep puddle, the immediate flow of water from under the wheel causes a sharp cooling of the diodes, in my practice this is the reason for their failure in 80% of cases.
Oleg
Failure of the bridge diodes can be detected by the battery being undercharged. On my Chevrolet Niva, due to the failure of the reverse diode, the lamp on the panel was constantly dimly lit. When I disassembled the generator, I simply rang all the diodes with a multimeter - one was broken. I bought a diode in the radio tent (there are no Russian ones, only an imported analogue) I soldered and assembled the generator. All work for 12 rubles. and an hour of work. At the service center, they first offered to change the generator - work + generator cost about 5,000 rubles.
Sergey
I have a special relationship with the generator: two of my cars had the same problem. First, the battery of one car began to be undercharged (there was no charge indicator lamp on the panel), and the charging lamp of another began to glow dimly. For both cars I followed the same path: first I measured the battery charge voltage at the terminals. Then I changed the “tablets”, and only lastly did I disassemble the battery. In both cases, the diode in the horseshoe is broken. In the first case, I couldn’t find the diode (this was during times of shortage), so I replaced the horseshoe. I remember it cost about 200 rubles. In the second case, I found an imported analogue in the directory. I bought it (15 rubles), resoldered the diode and all the problems went away. But in neither case, as the author of the article writes, was the second diode affected. By the way, the service offered replacement of generators and nothing more.
Lyokha
I agree that you don’t have to be an ace in radio engineering to carry out simple measurements with a tester. I try not to get involved in auto electrics once again, there are specialists for this, but sometimes need forces it. From personal experience I came to the conclusion that serious breakdowns are rare. Usually, either the brushes are worn out or the wiring is broken (burnt out, poor contact). I sincerely advise you - do not rush to buy a new generator; in 49 out of 50 cases, repairs cost pennies (or are completely free).
Vasya
I doubt it's worth checking it with a tester at all. The average car enthusiast is only interested in whether the generator is working or not. To do this, simply disconnect one of the terminals from the battery with the engine running. If the engine does not stall, then the generator is working. This method is actually harmful to both the electronics and the generator. But nevertheless the most effective :)
Kolya
Here I read that it is recommended to check by disconnecting the terminal on the battery. So you can’t do this! If such a focus channel is on domestic cars (Zhiguli, Volga, Moskvich) where, in principle, everything is oak and analog, then on a serious foreign car you can easily end up buying a generator or, even worse, a control unit. But I think it still makes sense to measure the voltage on a running motor with a tester. If it begins to deviate from the standard 14.4 Volts, then this may indirectly indicate wear of the generator brush assembly. In this case, it’s better to be on the safe side than to be left without a charger in the middle of the road.
Sergey
The generator may be in good working order, but the indicator light may be flashing, which may indicate a problem with the wiring outside the generator. Therefore, self-checking is not so simple. It is better to carry out a full diagnosis by electricians at a service station, where they can determine in advance an unexpected breakdown and the percentage of wear. But there are advantages to self-testing - you gain certain knowledge and skills.
Dmitriy
A generator is practically an ordinary electric motor; if you spin it and connect a light bulb, it will start to glow - this is an elementary generator.
Its main malfunctions are: jammed bearings, one of the common problems with generators that have been in use for a long time; the winding of either the stator or rotor burned out, most often from high speed travel through water; failure of the brush assembly; failure of the relay regulator.
If the generator stops working, this can already be seen in the cabin - the battery emblem on the instrument panel will light up. You must react immediately, otherwise you may drain the battery. The second signal is a dim glow of all instruments, which means the car is running on battery power and not on a generator.
There are two ways to do this check. The first is a multimeter. We measure the voltage at the terminals with the engine not running - it should be 12.5 - 12.7 V. We start the engine - it should be 13.8 - 14.5, although some manufacturers say 14.8. Then we turn on the load - the voltage should not fall below 13.7 V. If it is lower, 12.8 - 13V, then the generator is not working, you need to check it.
The second method is the old grandfather's method. Do it very carefully!!! We turn on the engine, turn on the load and remove the negative from the battery. If the car continues to work, the generator is working, if it stalls, the generator is dead. So I checked it on a VAZ 2108, Mazda, Opel, Chevy Niva.
Irina
She worked at a service station. They didn’t make the generators themselves, they took them to a specialist for generator repair. And you’re talking about yourself here!
Danila
Well, first I want to answer the last commentators Dmitry and Irina. The test method by disconnecting the battery is fraught with failure of the car's brains; old cars had no electronics, except for the switch on the VAZ 2108 and there was nothing to burn there. The battery is a rather large load on the generator and when it is disconnected, a sharp increase in voltage is possible, which is fraught. Now Irina - your “specialists” didn’t do it themselves only because they didn’t want to waste time, but any driver versed in technology can fix the generator (except for rewinding it). Now to the check. I only check with a multimeter, if the voltage on the battery with the engine off is 12.4-12.6, then with the generator running it should be 13.5 - 14.5.
Igor
The generator is the most important part of the car; your ability to drive the car and battery drain depend on its failure. To prevent this from happening, you need to monitor the condition of the generator.
However, there are mandatory rules that, if followed, will prevent damage to the generator. This includes: checking the generator for a spark, i.e. for a short circuit, this also includes the connection of terminal “30” to ground; operation of the generator with the battery disconnected; any welding work on the machine with the generator turned on; checking generator diodes (horseshoes) with voltage more than 12 V.
To check the generator, I personally use a multimeter with a Krona battery, it is 9 volt. Most often the voltage regulator fails and to check it, I first warm up the engine for 10-15 minutes. Then, in the position of a voltmeter with a scale of up to 20 V, I measure the voltage between the generator ground and the “30” mark. The voltage should be in the range of 13.5-14.5 V. If it is lower or more, the regulator may have failed, I have a spare one and I use it to check.
In addition, you can check the voltage on the battery, it should be above 12.6 V.
For those who understand car electrics, there is also a check of the diode bridge, the return current and the excitation current of the generator.
Anton
On my Seven Zhiguli car, I have repeatedly had to repair or replace the generator. This is one of the bottlenecks on my car. There are two main problems of breakdown. The first is failure of the generator drive tension belt pulley bearing; the second is a breakdown of the generator rectifier bridge. For the first failure, the diagnosis is simple, the noise of the bearing can be heard far from the car, but the second reason can only be determined by removing the generator. If you have a device, you can also do diagnostics without removing it, but you will still have to remove it, since the bridge will need to be replaced.
