As you know, the generator unit is an integral part of any modern car. Thanks to this device, the battery is charged while driving, as well as powering all electrical equipment. But like any other mechanism, the generator can fail for various reasons. In this article we will tell you in which cases it is necessary to repair the generator armature and how it is diagnosed.
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Description of the generator armature
Before you test a node, read the basic information. The anchor consists of the following elements:
- contact rings;
- brush knot;
- collector;
- excitation winding;
- core.
The core of the device includes several sheets made of electrical steel, their thickness should be 0.5 mm. The core is mounted in the shaft, but if the armature diameter is very large, then in a cylindrical sleeve. As for the collector, it consists of copper plates, the number of which may vary depending on the design. The collector is assembled separately, after which it is pressed into the shaft by means of an insulating sleeve.
The winding is made in the form of several sections, their ends are mounted in special protrusions on the collector plates. With the help of the last section, the windings are connected to each other in series, forming a closed circuit. Windings can be wave or loop. In the first, the conclusions of the sections are connected to the collector node, and they are connected to each other in a wave-like manner. In loop devices, the leads are connected to the collector plates, and they are connected to each other directly on the collector.
Operating principle
The armature of the generator unit rotates as a result of the impact of the bearing shields, as well as the bearings themselves, mounted on the shaft. The shield itself, which is located next to the collector, is called the front. Behind this shield, on the shaft, there is a winglet designed to cool the device. To ensure the flow of air, as well as to remove heat, there are special openings in the shields, which are closed with protective covers with grids. There are also holes in the front shield, but they are necessary for servicing the constituent elements of the device.
The armature of the device is connected to the network through a brush assembly. The elements themselves are located on special holders, which are fixed on the so-called fingers. These fingers are located on a traverse, which, in turn, is fixed to the front shield or frame, depending on the design. The pressure of the brush elements can be adjusted, special springs are provided for this.
The number of so-called brush fingers corresponds to the number of poles, with one half of them having positive polarity and the other half negative. In general, the brush assembly divides the winding into several parallel branches, their number may also vary depending on the type of winding (the author of the video is Volodymyr Zagryvyi / Vladimir Zagryvyi).
The on-board network of the vehicle is connected to the generator unit through a special terminal box, where there is a board with terminal marks on the windings. To ensure the lifting or movement of the generator unit, there is a corresponding bolt on the upper part of the bed. A plate is installed on its body, where the manufacturer is indicated, as well as the main technical data about the device. One of the main disadvantages of the generator device is the rather high complexity, as well as the too weak strength of the brush assembly, as a result of which the device needs periodic diagnostics and maintenance.
Typical malfunctions
There is an opinion among our compatriots that one of the main malfunctions of the anchor is the lack of resistance. It should be noted that the resistance is checked on the rotor winding, and the rotor, in turn, can be installed instead of the inductor, and the stator will stand instead of the armature. This is done in order to provide higher power, so the resistance can only be diagnosed on the rotor.
As for the anchor, it is characterized by such malfunctions:
- most often do-it-yourself repair of the generator armature is carried out as a result of slip rings wear;
- also, the need to repair the assembly may appear as a result of failure of the shaft bearing;
- not so often, but still the problem of a short circuit of the winding occurs.
It should also be noted that there are breakdowns that cannot be repaired:
- collector wear up to a diameter of 8.6 cm;
- keyway wear.
Self-diagnosis
So we smoothly approached the issue of verification. If you do not know how to check the performance of the node in your car, then first of all make a visual diagnosis of the state of the device. If the check showed that there is no external damage, then a more thorough diagnosis is needed. Initially, you should check the winding for insulation failure; for dialing, you will need a multimeter or a test lamp.
Before checking, one wire from the lamp must be connected to the armature shaft, and the other in turn to touch the collector plates. At the same time, please note that when checking, the wire lugs must be securely insulated. In the event that the armature winding is shorted to ground, the light should flash.
To test the turn-to-turn circuit, you will need a special inductive device. The core of the device in this case is made of metal, and the coil is powered by the use of industrial alternating voltage. The anchor is installed in the prism of the core, after which it must be rotated around the axis, and an iron plate is connected to the metal. In the absence of short circuits, there will be no current in the winding (the author of the video is the Ramanych channel).
If there is a short circuit, then an electromotive force will be fixed in the closed turns. In this case, the alternating voltage will contribute to the formation of another magnetic field, so if it is, then vibration will appear in the iron plates connected to the armature. The presence of vibration may indicate that there is a short circuit in the turns, if this is the case, then the only option to solve the problem is to rewind the armature.
Ways to eliminate breakdowns and defects of the anchor
If the surface of the shaft of the mechanism is worn, then the knurling procedure will correct such a problem. The mechanism itself is mounted in a lathe, and the worn necks are processed. Their diameter will increase due to the iron that comes out of the formed depressions. When the processing is completed, the harnesses must be sanded so that their dimensions correspond to those to be used.
When the collector is worn, its defective elements must also be eliminated. This component is subject to turning, after which the insulation is cut into the plates to a distance of 0.8 mm. In this case, the groove width should be no more than 0.6 mm; a milling machine is used to cut through the insulation.
After milling, the steel of the anchor must be treated with a special nitroglyphthalic varnish, and the winding with insulating one. In this case, the drying of these elements should be carried out at a temperature of about 110 degrees for 10 hours. Not every service station will provide such conditions for repair, so it will not work to repair the anchor at home.
Video "How to repair an anchor using a lathe"
A visual instruction for repairing an anchor element using special equipment is shown in the video below (the author of the video is Volodymyr Zagryvyi / Vladimir Zagryvyi).
The generator is quite stable in operation. Its failure, as a rule, occurs due to environmental factors, for example, in the form of condensing moisture on contacts and metal, which causes corrosion and breakdowns, as well as as a result of mechanical wear of rotating parts.
To know how to check the charging of the generator, you need some basic knowledge about the device of the unit, its components and the concept of operation of some of its parts.
To measure electrical resistance, you will need a special control and measuring apparatus: the so-called multimeter or ohmmeter.
Before checking the generator winding with a tester, it is necessary, first of all, to inspect it for external damage to the insulation, burns in the winding resulting from short circuits. If damage is visible to the eye, the stator must be replaced. If no external damage is found, then we proceed to a step-by-step check of the integrity of the stator winding using an ohmmeter.
The stator must be disconnected, the winding leads must not come into contact with each other.
Need to check:
- no open circuit winding
- lack of short circuit of the windings with the body.
We put an ohmmeter on the dial and measure the resistance.
In the first case, the ohmmeter tips are connected in turn to each of the three winding leads. With a faulty winding, the control device will show infinite resistance (i.e. one in the left digit of the digital multimeter and the maximum deviation to the right if the multimeter is analog).
In the second case, the ohmmeter tips are connected to the winding output and to the stator housing. In the presence of a short circuit, the control device should show a low resistance.
A serviceable stator, therefore, in these two tests should show a small resistance in the first case and an infinitely large one in the second.
Checking the health of the voltage regulator in the generator
Before checking the generator voltage regulator, it must be dismantled and disconnected. Next, you need to make sure that the brushes are intact, have no defects and chips, and move freely in the channels of the brush holder. Brushes protruding less than 4.5 mm require replacement of the voltage regulator.
The voltage regulator is directly checked using additional power sources: 12-14 V and 16-22 V.
Accordingly, the first source can be a battery, the second source is a battery with 1.5-volt batteries connected in series to it.
The positive output of the battery is connected to the output of the device, the negative - to the mass of the voltage regulator. A 12-volt light bulb is connected between the brushes.
If the regulator is in good condition when voltage is applied:
- 12-14 V light bulb should be on;
- 16-22 V, the light should go out.
In all other cases, the voltage regulator is defective, cannot be repaired and must be replaced with a new one.
Checking the capacitor for performance
A rough check of the capacitor can be carried out by charging it for several seconds with a voltage not exceeding the maximum indicated on it, after which closing its contacts with an iron object insulated from the hands. If the capacitor is in good condition, i.e. with its ability to charge and store a charge, a spark should appear.
Before that, 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 put the control device on the ringing and measurement of resistance. Then we connect the ohmmeter contacts in accordance with the polarity of the capacitor. A serviceable capacitor begins to charge, the resistance indicator will increase until it starts to go to infinity. Such results for a working capacitor.
For the arrangement of channels for wiring and pipelines, a wall chaser is used. This tool does not have to be purchased ready-made in the store. It will be much more economical to make from a grinder and other improvised elements.
It will be useful for any radio amateur and electrician to know the different characteristics of small parts and other electrical equipment. For example, you can read about the principles of operation of a power regulator on a triac, but it reveals the features of the color marking of resistors.
A non-working capacitor will:
- cause the ohmmeter to squeak and show zero resistance;
- immediately show infinite resistance.
Non-polar capacitor test.
We set the megaohm values on the control device and touch it with the contacts of the capacitor leads. At low resistance values (less than 2 mΩ), the capacitor is most likely in a non-working state.
Checking the diode bridge of the generator with a multimeter
The task of rectifier diodes is to correctly pass current in the direction from the generator and block its passage in the opposite direction. Any deviation in its operation is considered a failure of the diode bridge. Let's take a closer look at how to check the diode bridge of the generator.
First you need to remove the diode bridge from the generator and disassemble it to gain access to the diode contacts. The soldered leads on the stator need to be unsoldered.The multimeter switch must be set to ring. Diodes are semiconductors, belong to microelectronics. To ring a diode bridge, you need to understand its structure and have a circuit diagram.
Checking power diodes.
The negative terminal of the multimeter is connected to the plate of the diode bridge, the positive terminal is connected to the diode output. The current must pass. The instrument readings should tend to infinity. We connect the positive probe of the multimeter to the plate of the diode bridge, the negative one - to the output of the diode. The multimeter should show a resistance of 400 to 800 ohms.
Checking auxiliary diodes.
We connect the negative output of the multimeter to the auxiliary diode plate, the positive output to the diode output. The multimeter should show a value between 400 and 800 ohms. We connect the positive contact of the multimeter to the auxiliary diode plate, the negative contact to the diode output. The instrument readings will tend to infinite resistance.
Bearing inspection
A bearing is a mechanical part whose failure is due to a change in its physical properties. These can be corrosion, cracks, wear, damage, backlash, difficulty in rotation. An external sign of a problem with the generator bearing is the hum and noise emitted by the generator.
In this case, the rear bearing is removed and examined for the aforementioned part defects. The bearing ring must be able to rotate freely without creating extraneous noise.
If we talk about a car generator, then its front bearing is usually mounted in a cover. Checking is carried out according to a similar principle, rotating the cover and holding the center. The bearing should not seize or make noise.
Bearings with poor rotation or misalignment must be replaced.Thus, checking the generator for operability is not very difficult. The main thing is to understand the essence of the processes occurring in the device. The fundamental problems that happen to the generator are simple and standard. Armed with a multimeter and the knowledge gained, you can easily find a malfunction in the generator.
We look at how to check the generator with a multimeter, in the video
There can be at least two malfunctions in the generator stator of VAZ 2108, 2109, 21099 and their modifications. This "cliff" in his windings and short circuit
windings to ground. A sign of a generator malfunction is the disappearance of the charging current. In this situation, after starting the engine, the battery discharge lamp on the instrument panel goes out, the voltmeter needle tends to the red zone. If you measure the voltage at the battery terminals with the engine running, then it will be lower than the 13.6 V required from the generator 37.3701. In some cases, if there is a short circuit in the stator windings, the generator emits a characteristic howl.
Required Tools
- , autotester or other similar device with ohmmeter mode
- In the absence of a measuring device, a test lamp is required (a 12 V lamp with two wires soldered)
Preparatory work
- Remove the generator from the car engine
- and remove the stator
- We clean the stator from dirt
Checking the generator stator 37.3701
Checking for a "break"
We press the probes of the multimeter in ohmmeter mode to the terminals of the stator winding. If there is no "break", the device will show resistance within 10 ohms. If there is a "break" in the stator windings, that is, the current does not pass through them, then the resistance tends to infinity. We check in this way all three conclusions in turn.
checking the stator windings of the generator 37.3701 for an "open" If we use a test lamp, then we apply a minus from the minus of the battery to one of the terminals of the stator winding (using an insulated wire), and a plus through the test lamp to the other output. The lamp caught fire - everything is normal, no - "break". We repeat the operation in turn for all the conclusions.
Checking for a short circuit
We press the negative probe of the multimeter in ohmmeter mode to the stator, and the positive probe to any winding output. If there is no short circuit, the resistance on the device tends to infinity. We repeat the operation for each winding output.
checking the generator stator 37.3701 for a "short circuit" When checking the generator stator for a short circuit with a test lamp, we apply a minus from the battery output to the stator, and a plus through the test lamp to any winding output. The lamp lights up - there is a short circuit, no - everything is normal. We repeat the procedure for each output.
Notes and additions
- It should be noted that similar symptoms (except for the howl of the generator) may appear if the voltage regulator, diode bridge, generator rotor malfunction. Since a generator stator malfunction is much less common than a regulator or diode bridge malfunction, it is worth checking them first, and then proceeding to check the stator.
The generator is a kind of power plant that provides energy to all engine systems: power, cooling, ignition, so its failure will inevitably lead to other malfunctions. In order to prevent a breakdown, it is necessary to systematically diagnose it, and if it was not possible to avoid problems, immediately repair it.
In this article we will talk about how to work without resorting to the help of specialists. But first, let's look at the symptoms of its possible malfunctions.
The main signs of a generator malfunction
The following signs will tell you that the generator is out of order, or there are malfunctions in its operation:
- the constant burning of a signal lamp in the form of a red battery on the dashboard, which indicates that or is producing insufficient current;
- constantly discharging battery;
- interruptions in the operation of electrical equipment (lighting and signaling, multimedia, heating and ventilation units) with the engine running;
- the appearance in the cabin (engine compartment) of a characteristic burnt smell;
- excessive heating of the generator stator;
- hum (rustle, whistle) of the generator.
The appearance of such signs is a serious reason for diagnosing. To do this, it is not at all necessary to contact a service station, since it is quite possible to check the generator for performance on your own, especially if you have even the slightest skills in handling a car tester. But first, let's talk about the main breakdowns.
Major faults
The generator may have malfunctions of both a mechanical and electrical nature. These include:
- failure of the voltage regulator;
- malfunction of the diode bridge (rectifier unit);
- short circuit of the excitation winding of the rotor;
- short circuit of the stator windings;
- brush wear;
- bearing wear.
Checking the voltage regulator
The regulator is designed to stabilize the generated voltage before supplying it to the car's on-board circuit, including the battery for recharging. To determine its serviceability on your own, you can only check the charging of the generator, or rather, the amount of voltage supplied to it. Depending on the brand and model of the machine, it can be from 13.5 to 15.5 V. Therefore, before checking the operation of the generator for the health of the regulator, you need to know exactly what voltage it should give out. This information can be found in the vehicle's owner's manual.
How to check the generator with a multimeter? To do this, switch the device to the voltmeter mode and, observing the polarity, connect its probes to the battery terminals with the engine off. Voltage within 12-12.8 V is considered normal. Next, start the engine and repeat the procedure. The voltage at the battery terminals should rise to 13.5-15.5 V. Only in this case can the regulator be considered operational. An increase or decrease in the voltage value, on the contrary, indicates that it is faulty.
How to check the diode bridge of the generator without removing it from the car
It acts as a kind of rectifier, converting the alternating current generated by the generator into direct current. Usually it consists of six, and three of them are “positive”, the other three are “negative”, i.e. the first pass current in one direction, the second in the other. The rectifier can be checked both with the generator removed and without dismantling it. Let's consider both options.
Before checking the diode bridge of the generator without removing it, it is necessary to disconnect all wires from it and from the voltage regulator, after disconnecting the ground terminal from the battery. First, let's check the rectifier for Turn on the multimeter in ohmmeter mode, connect the positive (red) probe to the terminal "30" of the generator (positive contact of the bridge), and the negative one to the generator case. For a working rectifier, the readings of the device will tend to infinity. If the resistance is several ohms, the rectifier is faulty.
Now let's talk about how to check the diode bridge of the generator for breakdown. Let's start with the positive diodes. Again, we connect the positive probe to the corresponding contact of the bridge (pin "30"), and the negative probe to the bolts (brackets) of the rectifier. The resistance should also tend to infinity. Otherwise, one or more diodes are broken.
Let's move on to the "negative" semiconductors. We attach the red probe of the tester to the rectifier mounting bolts, the black probe to the generator housing. The resistance tending to infinity is a sure sign that the diodes are intact.
Checking the rotor winding
A common malfunction of a car alternator is the short circuit of the windings. This can happen as a result of a sudden power surge, water ingress, brush wear, etc. Since you can check the generator with a multimeter for the integrity of its windings, only having full access to them, you will need to dismantle the entire assembly. We will not describe this process, since it differs for different cars. Before checking the removed generator for the operability of the rotor winding, it naturally needs to be disassembled.
After removing the rotor, we find slip rings on its shaft. There are only two of them. Turning on the multimeter in ohmmeter mode, we connect its probes to these rings. The device should give a resistance in the range of 2-5 ohms. These are normal indicators for a serviceable rotor. A higher resistance indicates poor contact between the rings. In the opposite case, when the readings of the device approach zero, most likely, an interturn short circuit occurs.
How to check the generator for the operability of the stator windings
Let's move on to the stator. It has several windings, each of which must be checked separately. But before that, it is imperative to disconnect the wires connecting the terminals of the windings and the diode bridge.
The probes of the multimeter, switched on in ohmmeter mode, are connected in turn to the terminals of each of the windings. The working winding should have a resistance of about 0.2 ohms.
Generator brush wear
If the generator has already been dismantled and disassembled, it does not hurt to check the condition of the brushes. They can fail due to prolonged use, or as a result of problems caused by misalignment of the rotor shaft. If the brushes show signs of heavy wear, their geometric shape is broken, they must be replaced.
Generator bearing wear
The car alternator has two bearings. One of them is fixed on the rotor shaft, the second is pressed into the central part of the cover. A hum, a whistle coming from the side of the generator while the engine is running, is a sure sign that one of the bearings has died. An accompanying symptom may be heating of the generator housing. If you find these signs, hurry to replace the bearings. Otherwise, this will lead to a misalignment of the rotor shaft or its jamming with all the ensuing consequences.
You can check the bearings by removing the alternator belt and turning its shaft by hand. If the rotor rotates easily, without jerks and play, the bearings will still serve. If rotation is difficult or the shaft has play, do not hesitate to replace the bearings.
The malfunction of the car generator belongs to the critical class, in which further operation of vehicles is not allowed. A multimeter can be used to perform a health check on the generator.
Signs of abnormal operation of the car generator may be:
- no "battery" indication on the dashboard when the ignition is turned on;
- the glow of the "battery" light after starting the engine;
- periodic blinking of the signal indicator "battery" in the process of movement;
- the smell of burnt electrical wiring in the generator area;
- failure to start the engine after parking.
The lack of battery charge with a faulty generator leads to problems with starting the engine. More dangerous is a malfunction associated with an excess of current and voltage of the car battery charge. Many motorists use to start the engine from a donor battery, after which they disconnect the battery terminals to switch to charging their own battery. At this point, the electrical equipment of the car is powered by a generator.
If the generator is faulty, the voltage in the on-board network may be more than 17 volts, which leads to a breakdown of the protective zener diodes in the engine control unit. In this case, an expensive repair of the engine control unit is required.
Causes and possible consequences of a malfunction
Generator failure is possible for the following reasons:
- malfunction of the voltage regulator (“pills”, “chocolates” in the slang of motorists);
- wear (destruction) of brushes;
- short circuit of the exciting winding (rotor);
- breakdown of diodes (located in a horseshoe);
- wear of bearings and bushings.
A faulty voltage regulator usually results in no battery charge. In this case, the indicator icon "battery" is lit on the dashboard. The engine continues to run until the battery is discharged to approximately 8 - 9 volts.
During daylight hours, a battery charge can last for 30-50 kilometers, provided that the battery was well charged at the time of the malfunction.
In the event of a breakdown of the output stages of the voltage regulator, a malfunction may occur associated with an increase in the output voltage of the generator to 17 - 20 Volts. This will recharge the battery. The consequence of overcharging is the process of boiling the electrolyte. If there are signs of corrosion under the hood in the area of the battery, it is necessary to check the generator.
Breakdown of the diode bridge can occur when the battery is accidentally reversed (terminals are installed in the wrong polarity). Usually diodes break through in pairs in one shoulder. A faulty diode has a resistance close to zero. The stator winding of the generator in this case operates in short circuit mode, becomes very hot.
After a few minutes of engine operation, the windings overheat, a smell of burnt electrical wiring appears under the hood of the car. To avoid ignition, the engine must be turned off, the generator must be checked.
The wear of the brushes leads to the gradual failure of the generator. First, while driving, the charge indicator light on the dashboard starts blinking, then it starts to glow constantly. In many generator models, the brushes are changed together with the voltage regulator.
Closing the generator windings can lead to a significant change in the output parameters, overheating of the device.
Sequence of initial check
An initial performance check can be made without dismantling the generator. To do this, set the multimeter switch to the "constant voltage 20V" mode. Next, connect the black probe to the negative terminal of the battery, the red one to the positive one. After that, you need to start the engine, let it go to a stable idle mode. Multimeter readings ranging from 13.5 to 14.5 volts are considered normal.
If the multimeter shows a value less than 12.8 volts, the charge process either does not go at all, or the charge current is extremely small. The generator is operating abnormally. At a voltage of more than 14.8 volts, the battery is being recharged. This can lead to boiling of the electrolyte, an increase in the concentration of acid, and destruction of the battery plates.
To control the voltage at the output of the generator, it is necessary to turn on the car lamp in an open circuit from terminal 30 on the generator (the place of contact with a thick wire leading to the positive terminal of the battery or starter).
Next, connect the multimeter in the "= 20V" mode with a red probe to terminal 30 of the generator, black - to a stripped contact on the engine or body. Start the engine. The readings on the multimeter should not be more than 15.5 volts with any press on the accelerator pedal. Otherwise, further operation of the generator is dangerous for the vehicle's electrical equipment.
When checking, the degree of tension of the alternator belt should be assessed. Using a simplified method, this can be done by pressing on the belt with your finger.
The deflection value should be in the range of 0.5 - 1 centimeter. At the same time, the degree of belt wear should be checked.
To determine the causes of abnormal operation of the generator, to perform repair work, it is required to dismantle the generator.
Checking generator nodes
The test begins with monitoring the performance of the voltage regulator. To do this, the regulator is dismantled from the generator and a simple electrical circuit is created.
As an incandescent lamp, any car interior light bulb is used. With a working voltage regulator 3, lamp 6 should not glow at full power. When connected in parallel with the lamp (brushes) of the multimeter, its readings should be from 5.0 to 10.0 Volts. If the multimeter readings go outside these limits, the regulator must be changed. The design of some generator models provides for the possibility of replacing the regulator without dismantling the device.
Further, the exciting winding of the generator is checked for breakdown. To do this, the multimeter is set to the resistance measurement mode to the limit of 200 kilo-ohms. The probes are connected: black - to the collector lamella, red - to the metal part of the armature. The resistance must be more than 100 kilo ohms or higher than the upper limit of measurement, as shown in the photo.
The resistance between the lamellas (rotor windings) is usually 0.5 - 2 ohms.
The stator check begins with the control of the windings for breakdown. To do this, the red probe of the multimeter is connected to the metal part of the stator, the black one is connected in series to the windings.
The resistance must be above the upper limit of measurement. Then measure the resistance between the contacts of the windings. They should differ by no more than 5%. The measurement limit of the multimeter is set to 200 ohms.
If the winding has an electrical breakdown, a short circuit of the turns or an open circuit, it must be replaced. There are workshops that rewind stators and rotors.
To monitor the health of the diode bridge, the multimeter measurement mode is transferred to the “diode” check. Then the diodes “ring out” in series (their number on the horseshoe is usually 9) in direct and reverse connection. In the forward direction (black probe to the cathode), the resistance is 550 - 700 ohms, with the reverse connection - more than the maximum measurement limit.
When the diodes break down, the resistance in all directions will be almost zero. Such a diode should be changed. The difficulty of replacing the diode lies in the fact that the diodes in the generators are not soldered, but are welded by spot welding to ensure reliable contact at different temperature conditions.
The car's alternator is a significant part of the car's electrical equipment. At the first manifestation of signs of inoperability, it is necessary to check it with a multimeter.
