A malfunction of the generator rotor of VAZ 2108, 2109, 21099 (37.3701) cars primarily leads to the disappearance of the charging current and discharge of the battery. After starting the engine, the battery discharge light on the instrument panel will be constantly lit, indicating that there is no charging current. The voltmeter needle is in the red zone or on the border with it. If you check with a voltmeter (multimeter, tester, etc.) the voltage at the battery terminals with the engine running, it will be lower than the required 13.6 V.
Malfunctions of the generator rotor can be a short circuit in its windings and separation of the excitation winding leads from the slip rings - a “break”.
Tools needed to check the rotor
, tester, voltmeter, etc.
If they are not there, then control lamp - a 1-5 W, 12 V light bulb with wires soldered to it.
Checking the generator rotor of VAZ 2108, 2109, 21099 cars
Checking for short circuits and open circuits can be done without removing the generator from the engine or removing the rotor. We remove the voltage regulator and, through the window that opens, carry out the manipulations described below.
Checking the short circuit of the rotor excitation winding to ground
— We press the plus of the multimeter in ohmmeter mode one by one against the slip rings, and the minus on the generator housing (“ground”).
If the rotor is working properly (there is no short to ground), the resistance should tend to infinity.
When using a test lamp, it is necessary to pass through it, in turn, the plus from the battery to each of the contact rings of the “excitation” winding of the rotor. The minus will be the generator housing, since it is installed on the car and connected to the battery negative. If the rotor is working properly, the control lamp should not light up - plus and minus do not meet anywhere. Otherwise it will burn.
checking the excitation winding of the generator rotor 37.3701 of VAZ 2108, 2109, 21099 cars for a short circuit The plus of the multimeter (in ohmmeter mode) is on one contact ring, the minus on the other.
When the excitation winding is in good condition, the resistance is in the range of 5-10 Ohms.
If a test lamp is used, then we connect the plus from the battery through it to one contact ring, and the minus with another wire to the second contact ring. The lamp should be on. If this is the case, then the “excitation” winding is working.
checking for a “break” in the excitation winding of the generator rotor 37.3701 of VAZ 2108, 2109, 21099 cars The rotor winding leads that have come off the slip rings can only be seen after removing and. In some cases they can be soldered. Most often, the faulty generator rotor 37.3701 of VAZ 2108, 2109, 21099 cars should be replaced.
winding terminals and contact rings of generator 37.3701 for VAZ 2108, 2109, 21099 cars Notes and additions
The car battery supplies it with electricity in splendid isolation only until the engine starts. After the engine starts, the generator helps it. The task of the generator is to ensure continuous recharging of the battery in all operating modes and under any load on it. But breakdowns happen. How to determine that the generator is to blame?
Signs of its malfunction are:
Nature of the malfunction | Cause of malfunction |
| The battery is boiling over | Large charging current |
| Battery is running low | Charging current is low or absent |
| The “Lack of battery charge” light on the car’s instrument panel is on. | No charging current |
| The voltage in the on-board network is unstable | There is no stabilization of the charge current or there is no current. |
| Extraneous sounds in the generator | The bearings require replacement or the alternator belt is not tensioned. |
But first things first. The generator is not so easy to remove and to do this, you need good reasons.
Diagnosing a generator on a car with a multimeter / tester
Checked before inspections tension and technical condition alternator belt. The belt should not be overtightened, but it should not be loosened either. In the first case, the bearings will wear out prematurely, in the second, the rotor will slip when the electrical load increases. Slippage, in addition to reducing the voltage in the network, will also lead to premature wear belt The belt itself should not be worn out and there should be no cracks on it.
If you smell burnt rubber from under the hood while the engine is running, the “no charge” light comes on - Generator bearings are jammed. Increased noise, on the contrary, is caused by a reason increasing the gap in them. This is checked by loosening the belt and shaking the rotor shaft in the radial direction. This only determines the play in the front bearing, but it is the one that suffers first.
If the mechanics are in order, check the electrical characteristics. To do this, you will need a device capable of accurately measuring a direct voltage of 12 - 16 V. Moreover, the scale (or digital indicator) at this measurement limit must show values with tenths, otherwise the measurements are meaningless. Both a pointer tester and a multimeter are suitable.
We connect the device directly to the battery, observing the polarity. For digital instruments, reversing the polarity will not harm, but for analog instruments the needle will sharply hit the left limiter. You shouldn’t be afraid of this, the device will withstand it, but it’s not advisable to stay in this position for a long time.
It is better to fix the measuring probes on the terminals. You can use the services of an assistant, but using alligator clips is more convenient. The main requirement is that when the motor starts (it jerks) the clamps do not turn off spontaneously.
Before starting the engine fix the battery voltage. It should be between 12.5 - 12.7 V, depending on the degree of its charging, and the entire load is turned off. Don’t forget that when you open the doors, the light comes on in the cabin, and this is a small, but load. If the voltage is below 12 V, then it is better to charge the battery before the test. A working regulator will greatly reduce the voltage, trying to correct the situation and charge the battery as quickly as possible. And you will draw incorrect conclusions from this about its malfunction.
Now start the engine, warm it up so that the rpm is equal to the idle speed for your model (usually within 800). We control the voltage on the battery; you can start looking at the device scale while it is warming up. The measured value should be between 13.5 and 14 V. And so on in all operating modes.
If on idle speed voltage is below 13.0 V, then the problems may be as follows:
Malfunctions associated with broken contacts
You need to constantly monitor the cleanliness of the battery terminals, but you should not use sandpaper to clean oxides. It is better to scrape with a knife, and periodically loosen the contacts and grind the surfaces, turning the clamps on the terminal from side to side. And when checking the oil level, apply a couple of drops to the battery contacts.
Contact connections that should be checked in case of low charge voltage:
- Positive terminal: from battery to generator;
- Negative terminal: from the battery to the car body; from the car body to the engine housing.
Contact between the car bodies and the engine of VAZ models is ensured flexible connection under the bottom in the area of the gearbox. The metal lead bends and additional resistance is added to the electrical circuit. And the minus of the generator is connected to the minus of the battery through it. Additional resistance is also introduced by rusty elements of the bodies of old cars.
The way out is to install an additional flexible connection from a 25mm2 conductor connected between any of the suitable bolted connections on the engine and the connection point of the negative terminal of the battery to the body.
Battery faults
When the battery plates become sulfated and their service life expires charging voltage does not increase. The battery itself acts as a limiter. To make sure of this, try to fully charge the battery. If it doesn’t work, replace it with a new one.
If the voltage on the battery is more than 14 V when the generator is running, then either it is very discharged or the voltage regulator is faulty.
Diagnostics of the voltage regulator operation
The task of the voltage regulator is maintaining battery voltage in the range from 13.5 to 14 V at all engine operating modes and at any load. Criteria for its performance:
- When you press the gas pedal and increase the engine speed, the voltage increases slightly, without leaving the permissible limits.
- When consumers are turned on: headlights, car radio, heater, air conditioner, the voltage drops below the permissible value only by Idling. If you increase the speed (add gas), it returns to the operating range.
Check the serviceability of the regulator with the engine running by changing the speed by pressing the gas pedal. First, the experiment is carried out without load, then the headlights and heater are turned on, adding load. The voltage on the battery should not change significantly.
If this is not the case, the regulator is changed. On some models this is possible without removing the generator, but it is still recommended to remove it. Purpose: to further evaluate the condition of the brushes, remove dirt accumulated during their operation, and check the condition of the bearings.
Checking the generator brushes
To inspect the generator in detail, it is removed from the car. Then it is cleaned of contaminants. Remove the brush apparatus and, if necessary, the voltage regulator. The brushes must be worn evenly (their length is the same, and the wear from the rotor rings is symmetrical relative to the longitudinal axis). The remaining length of the brushes should be more than 4.5 mm (8-10 mm is considered the norm). If these parameters are not met, the brushes are replaced, even if the fault does not lie in them.
Along the way, you will need to remove the carbon dust formed when the brushes rub against the rotor rings.
To replace the voltage regulator or brushes, no further disassembly is required, but if the fault has not yet been found, open the back cover of the generator. Before this, you will need to unwind the positive output pin.
Checking the rectifier
The generator produces three-phase voltage, rectified by six diodes. The positive and negative terminals of the rectifier are made in the form of aluminum plates, which at the same time serve as radiators for cooling the diodes.
To check their serviceability, you will again need a multimeter or tester. We switch the device to resistance measurement mode. Then we measure the resistance of each diode in the forward and reverse directions one by one. To do this, change the polarity of connecting the probes of the device. In the forward direction, the resistance is low (but not zero). In reverse it is equal to infinity. If this is not the case, the diode has failed.
If one diode is damaged, at least two more fail. It is impossible to accidentally leave a breakdown unattended. The diodes are replaced as a group, together with the radiator.
Generator stator diagnostics
The stator winding is made of thick wire, so breaks in it are rare. Unless the contacts are unsoldered at the places where it is connected to the diodes, which needs to be checked.
Then inspect the winding for mechanical damage. They appear if the rotor shaft, due to increased bearing wear, has shifted to the side during operation. At the same time, its impeller touches the turns of the stator winding and damages them. Result: breaks, turn shorts or shorts to the housing.
The insulation of the stator conductors is restored. To do this, varnished fabric is laid between the turns. For fixation, the damaged area is coated with bakelite varnish and dried. The use of insulating tape is unacceptable; it will melt under the influence of the operating temperature inside the generator.
With absence visible damage it is possible for the winding turns to short-circuit between each other and to the housing. A turn fault can only be detected by a change in the color of a group of winding turns. It will not be possible to identify a defect by measurements, since the cross-section of the wire is large, and the number of turns, on the contrary, is small. The change in resistance across phases is so small that it is comparable to the transition resistance at the point where the probes of the device are connected. But the likelihood of a turn short circuit occurring, fortunately, is small.
But short circuits to the housing occur more often. To identify them, measure the resistance between any winding terminal and the housing. Use the highest limit of the multimeter to measure resistance. It is better to use a special device - a megohmmeter, but only on condition that the voltage it produces does not exceed 100 V. The operating voltage of the generator is 12-16 V; using megohmmeters for testing higher voltages will damage the insulation.
For any problems with the stator winding, the best solution is to replace it. The stator is sold with a winding wound inside it. But rewinding it yourself, even with the involvement of specialist wrappers, will not justify itself.
Generator rotor diagnostics
When inspecting the rotor, pay attention to:
- wear on the slip rings: there should be no grooves formed under the brushes;
- winding color: uniform, other than black (black color – the winding is burnt out).
To level the surfaces of the slip rings, they can be ground by holding the rotor in a lathe, making sure to center it. For grinding, sandpaper is used, the grain of which is reduced as it approaches the desired shape of the rings.
To diagnose the rotor winding, its resistance is measured with a multimeter or tester. U different models generators this value fluctuates from 2.3 to 5.1 Ohm.
Generator bearings
Pullers are used to remove bearings. The use of improvised means for this purpose is possible only if you have the appropriate experience.
If during diagnostics of the generator it turns out that more than two of its parts need to be replaced, it is better to purchase it entirely. And if you are not confident in your abilities, immediately use the services of specialists from the nearest service station. This way you will save your time, nerves, and possibly money.
First we remove the positive «+»
terminal from the battery to avoid accidental short circuit, then disconnect all contacts from the generator and, bending the latches, remove its back cover (the design of which provides for this). In this way we can carry out a general check of the diode bridge and stator winding, as well as the rotor. To check the voltage regulator, you must remove his from the car's generator.
 |
| Fig.2 |
Fig.3
1. First, check the generator for a short circuit to ground.
We press positive «+»
multimeter probe to the terminal "thirty"
generator, and negative«-»
probe to its body. In good condition, the diode bridge does not pass current in this direction, there is no sound signal, and the light bulb does not light up.
2. Check the positive diodes for breakdown.
Positive «+»
press the multimeter probe to the terminal "thirty"
generator, negative «-»
to the terminals of the winding and diodes (generators type 9412.3701, where the bolts are insulated from the terminals with textolite washers and are closed to "mass"
), or one of the axle mounting bolts (type generators 37.3701,
where the bolts are connected to the leads but are isolated from"masses"
- Fig.5).
If the diodes are working properly, then the resistance tends to infinity, and the light bulb does not light up. Even if one of them is “broken,” the light comes on, hearth multimeter There is no sound signal.
3. Check the negative diodes for breakdown.
To do this, press the positive «+» multimeter probe to winding and diode terminals 37.3701 - Fig.5). Negative «-» press it against the generator housing.
If the resistance tends to infinity and there is no sound signal, the lamp does not light - the negative diodes are working.When changing polarity, they must pass current.
4. We check additional diodes for breakdown.
We press positive «+» multimeter probe to the input "61" generator Negative «-» probe to the terminals of the winding and diodes (generators type 9412.3701), or to the axle mounting bolts (generators type 37.3701 - Fig.5). If the resistance tends to infinity and there is no sound signal, the lamp does not light - the additional diodes are working. When changing polarity, they must pass current.
To determine a break in the diode you will also have to
.
It is worth noting that checking diodes with a multimeter and, to a lesser extent, with a light bulb, in which diodes are checked under load, are not 100% accurate. effective method. For this, there are more accurate instruments, such as an oscilloscope.
If the diode bridge is working properly, then we proceed to checking the stator winding.
5. Check the stator winding for an open circuit.
We alternately connect the multimeter probes between all three terminals of the stator winding.
A sound signal or a lit lamp in all three cases tells us about the integrity of the winding.
6. Check if the stator winding is shorted to ground.
We connect the probe to one of the winding terminals, and the other to the generator housing. If the resistance tends to infinity, there is no sound signal, the lamp does not light - there is no short circuit.
7. Check the stator winding for interturn short circuit.
To do this, switch the multimeter to the “200 Ohm” resistance measurement mode and connect the probes between all three terminals of the stator winding. The resistance should be 0.2-1.2 ohms and be the same between all three terminals.
Gone are the days when car dashboards resembled the workplaces of aviation pilots - with a scattering of sensors, instruments and mechanical buttons. Nowadays, it is common practice among automakers not to fill drivers’ heads with “unnecessary” information. In particular, you will almost never find dashboard ammeter - in modern cars All that was left was the warning light. If she shows anything, it will be when the trouble has already happened. But if the generator breaks down, the car practically cannot continue moving (at most, it will travel a couple of kilometers on the battery), and there is a possibility of getting stuck in the middle of the road. Is there any way to check the generator and protect yourself from an unpleasant situation? Can.
In the photo: a generator under the hood of a car
What can break down in a generator?
To better understand what can break down in a generator, you need to understand its structure. It is not as complicated as it might seem. To put it simply, the generator consists of:
Housings,
The moving part (rotor),
Fixed part (stator),
And additional elements, which include a relay regulator, a diode bridge, and a brush assembly.
The main enemies of the generator are time, water, chemical reagents and mechanical damage. They cause all the problems.
1. The most popular reason for generator failure is brush wear. They are graphite and follow the paths of the rotor, so they simply wear out with time and high mileage. Brushes are usually sold separately, are inexpensive and easy to replace.
2. A much less pleasant malfunction - failure of the relay regulator. If the generator maintains too high or too low voltage, then the problem is most likely in it. The relay regulator is more difficult to diagnose and replace than brushes, but this can also be dealt with at home.
New relay-regulator on the left, on the right - old
3. Seized bearings don't bode well. The rotor stops rotating, and without this the generator will not generate current. The bearings themselves are inexpensive, but replacing them requires experience and special tools, so it is better to carry out such work in a service environment.
Failed generator bearing
4. When diode bridge failure the generator becomes useless, because the unit itself produces alternating current, and for consumers in the car they need a constant one. This is exactly what the diode bridge does. This is a very sensitive element that is afraid of water, short circuits and reversed polarity. It can be repaired by changing diodes, but modern conditions The diode bridge is usually replaced, it's easier.
4. The most unpleasant type of breakdown is winding combustion on the stator or rotor. Purely theoretically, it can be restored, but usually in this case it is necessary to consider the feasibility of repair; often it will be cheaper to buy a new winding than to repair it.
How to diagnose a generator without removing it
You can understand how well the generator works without removing it from the car. The methods are very simple and accessible to any motorist.
1. You need to measure on-board voltage with a regular tester. Three measurements need to be taken. First, on an unstarted car (the device should show about 12.2-12.7 V, but this is an indicator of the health of the battery).
Then start the engine and turn off all consumers (the normal value in such a situation should be in the range from 13.8 to 14.7 V). Finally, you need to turn on several powerful consumers (heater, headlights) and measure again. The voltage will drop, this is normal, as it should be, the main thing is that the drawdown should not be lower than 13V. If the numbers turn out different, it is dangerous to drive with such a generator.
2. Take a closer look at the lighting fixtures– if the headlights or interior lighting have become dimmer than before, this is the first sign of low voltage in the network. Better on a car like this long journey don't go.
3. A very alarming symptom is flashing headlights in time with changes in speed. The relay-regulator is responsible for the “evenness” of operation in the generator; if it does not stabilize the voltage regardless of the crankshaft speed, then the machine will almost certainly “stop” soon. We urgently need to deal with this issue.
4. No matter how trivial it may sound, it’s worth taking a closer look and listening to the generator. Bearings and rollers rarely jam suddenly; the impending failure is almost always preceded by whistling, howling, or extra noise. If you hear extraneous noise from under the hood, you need to find its source. You can monitor the belt visually; it also wears out not in one trip, but gradually.
5. If you have an old carburetor car, then another, very simple diagnostic method is available to you. Enough reset the negative terminal from the battery with the car running, and look at the operation of the car - if nothing has changed, then the generator is doing the job, but if the car begins to work unevenly, intermittently, you need to find out the reason. Alas, this method is contraindicated for injection cars - it is difficult to predict how the fragile the electronic unit control during sudden voltage drops. If something happens, the ECU will have to be changed and diagnostics will be very expensive.
What else to pay attention to
Finally, indirect diagnostics of the generator can be carried out using the battery. They work in close conjunction, and the “health” of one can be used to judge the performance of the other. If the battery is used constantly, then the problem may be precisely a weak charge from the generator (although problems with the “battery” itself are also possible). It will come out sideways for the battery and too high voltage in the on-board network - if the battery suddenly boils over, then you need to diagnose the generator; such things don’t happen “just like that.”
It wouldn’t be a bad idea to just have the generator inspected. All its wires must be securely screwed in - without interruptions or kinks, the housing must not be damaged, and the unit itself must not spark during operation.
Diagnostics with disassembly
If preventive measures do not help, and the generator still breaks down, then it is necessary to dismantle the unit, disassemble it and diagnose it. If the problem unit is not noticeable, then you need to check all the components of the generator one by one.
1. Rotor. You need to check the winding for resistance with a multimeter, “connecting” probes to the slip rings. The resistance value of a serviceable winding lies in the region of 2.4-5.1 Ohms. If there are zeros on the multimeter display, then there is a break in the winding; if there is resistance, but very small, then there is an inter-turn short circuit somewhere in the winding; if the indicator is higher, you need to look at the contacts and solder the most unreliable ones.
Checking the generator rotor
2. Stator. He also needs to “ring” the winding. The “correct” value of the resistance between the terminals of the windings is 0.2 Ohm, otherwise there is either an open circuit or a short circuit. It is very convenient to check the stator insulation for breakdown with a regular 220 volt light bulb. If you connect it with one contact to the winding output, and the second contact to the stator housing, then it should not burn. If it lights up, it means there is a breakdown.
3. U diode bridge You need to check all diodes for current conductivity. To do this, you need to switch the tester to ohmmeter mode, bring one probe to the plate, and the second one in turn to the diodes that are pressed into this plate. Then the screws need to be swapped. And so check all the diodes in all plates. The diode bridge is working properly when there is resistance with one of the diode connections, but not with the other. Due to the fact that diodes have different charges, it is not worth remembering which connection should give resistance and which should not, the main thing is that in one of the two measurements each diode has resistance. If not, then the diode bridge needs to be changed.
4. Worn to the limit brushes It's the easiest thing to diagnose - you don't even need a multimeter. It is enough to measure their length with a ruler; if it is less than 4.5 cm, then the brushes need to be changed. It wouldn’t hurt to measure the diameter of the slip rings at the same time. It should be at least 13 mm, and even better, about 14 mm.
As you can see, checking a generator is not such a difficult task. Simple operations can be carried out directly on the machine, but even if the generator has to be removed and disassembled, there is nothing complicated there. A multimeter, a set of screwdrivers and wrenches will help you take all the measurements. Fortunately, spare parts for many generators are freely sold, so you can replace only the worn-out element yourself, without large investments, bring the generator back to life.
The task of the generator, as the main source of electricity in a car, is to generate and maintain voltage at a certain level, regardless of the level of load on the on-board network.
A fully operational unit should produce 13-14.5 volts.
Voltage stability is maintained by an electronic relay regulator, which in most cases is built directly into the generator. Its failure sharply limits the ability to operate the machine: in this case, the only source of energy will be the battery, which will soon be discharged. What breakdowns occur with this device, how to check the generator and what causes the breakdowns are discussed below.
Signs of a generator malfunction
Complete or partial failure of a device can be determined by the following symptoms:
- The warning light on the instrument panel, usually in the form of a picture of a battery, begins to flash or stays on. This indicates that the battery is not charging or the current supplied to it is insufficient.
- Constant failures in electrical equipment: unstable work external and internal lighting, when the lamps burn brighter or dimmer, heating when the engine is running (if the engine is turned off, then everything functions normally). By the way, problems with lighting can also be observed if necessary.
- Accumulator battery constantly and often discharges.
- There is a burning smell in the interior or engine compartment.
- A whistle or excessively loud rustling noise is heard from the generator.
- The generator makes a loud noise during operation: the diode bridge or stator windings are faulty.
The appearance of the above symptoms indicates the need for immediate diagnosis. But how to check the generator yourself? If you know how to use a multimeter, then diagnostics can be carried out without going to a car service center. However, first you need to determine the nature of the breakdown. Damage can be either electrical or mechanical.
Generator malfunctions and reasons for its failure
First, a little about the design of the device. The main components of the generator are a stator (fixed element), rotor (rotating part), brushes, a built-in relay-regulator unit, a diode bridge and a housing with bearings.
And now - about the most typical malfunctions:
- Bearing jamming. This problem most often occurs with a generator that has been in operation for a long time. Dirt, dust, and moisture gradually do their job: as a result, the bearings jam, the rotor of the device stops spinning and the drive belt breaks. There is a nuance here: sometimes the generator does not stop completely - it gets stuck. In this case, a characteristic whistle will be heard, indicating increased friction in the falling apart bearings. When replacing these elements, it is recommended to install two new ones at once (in the rear and front cover of the generator).
- Combustion, interturn short circuit of the rotor or stator winding. The reasons for this malfunction are also not original: moisture and salt on the roads, which in “steam” corrode the varnish insulation of the windings, resulting in a short circuit and ultimately burnout of the wires.
- Breakage or wear of the brushes. By design, they are graphite square or rectangular products in contact with the copper tracks (slip rings) of the stator. Most often the brushes wear out, less often they break. Sometimes their performance can be determined visually: put the car in a dark garage and start the engine, first opening the hood. Sparking inside the generator indicates worn brushes.
- Malfunction of the voltage regulator. This is an electronic unit whose task is to maintain the voltage at the same level, ensure the supply of rated current to the battery and prevent it from overcharging (which leads to boiling off of the electrolyte).
- Malfunctions of the rectifier unit. It consists of several electronic components that form a diode bridge. If at least one of them fails, the current stops being rectified, the functioning of the voltage regulator stops: the on-board network begins to be powered only by the battery, which has a limited service life.
How to check battery charging and generator performance with a multimeter
To carry out this procedure, it is not at all necessary to have a professional tester: a regular multimeter, which has modes for measuring resistance (ohmmeter) and voltage, will do. First you need to take measurements with the engine not running. Attach the multimeter probes to the battery terminals: the tester should show at least 12.5 volts (with a normally charged battery).
Now start the car and, without turning on any consumers, measure the voltage again: it should be in the range of 13.8-14.5 V. At the next stage, you will need to connect the load to the on-board network: the heater on full power, multimedia, headlights ( high beam), fog lights and heating rear window. Look at the device: if the generator is working, the voltage will drop to 13.7-14 V. If the value is lower, you will have to test the generator. The following describes ways to check the generator and its components without removing the device from the car.
Voltage regulator
The purpose of this block (some call it a “chocolate bar” or “tablet”), built into the generator, is to stabilize the on-board voltage. To check the generator with a multimeter along with the regulator, you do not need to remove the latter from the car. You will need to carry out the operation described above: that is, measure the battery voltage with the engine off and running. A deviation from the norm to a lesser extent indicates a malfunction of either the voltage regulator or the generator. But exceeding the parameter of 14.5 volts indicates a failure of the relay, which is fraught with constant boiling of the battery. To more accurately check the voltage regulator, it must be removed. This is not difficult and dismantling can be done directly on the installed generator: just unscrew 2-3 screws (the number depends on the car model). Further actions:
- disconnect the positive terminal from the battery;
- take the regulator and connect the “+” of the battery to its terminal (where the thin wire from the generator is connected), and connect the minus to the second contact of the relay (“ground”);
- To the brushes of the voltage regulator using wires, connect any car lamp, designed for 12 V;
- its glow will indicate the serviceability of the unit.
Checking the diode bridge without removing it from the car
The function of this block is to rectify a variable to convert it into a constant. The bridge most often includes 6 semiconductor diodes. Three of them conduct current only in one direction, three - in the other. To check the generator with a multimeter and at the same time the integrity of the diodes, you will need to remove the wires connected to the voltage regulator and generator. Don't forget to disconnect the "-" from the battery. Switch the tester to the resistance range. Connect the positive probe (it has a red tint) of the device to terminal “30” of the generator (the thickest cable stretched from the battery fits here), the negative probe (black) to the body (“ground”) of the device.
If the diode bridge is working properly, then the tester readings are infinite high resistance. If it is some ohm, then the rectifier needs to be changed.
Checking diodes with a multimeter on a dismantled and disassembled generator
The bridge includes a pair of aluminum plates: one of them is “negative”, the second is “positive”. Take the tester and place one of its probes on the plate, and with the other, touch the contacts of the diodes fixed on the plate in turn. The device should show infinity or resistance (usually several kiloohms). Then change the probes: you should get the opposite picture. We do the same with the second plate. If the readings on any diode are zero, it means it is broken and needs to be replaced. If all the diodes show a certain resistance, and one of them shows infinity, then this means a break: the electronic component also needs to be replaced.
Checking the rotor windings
When the generator brushes are not worn out and their length is 4.5 mm or more, and the diode bridge is intact, you can start checking the rotor. To do this, the generator will have to be removed and disassembled. The dismantled device must be divided into two parts by unscrewing the mounting bolts. On one of them you will see a shaft on which copper slip rings are fixed. How to check the generator in this case? You just need to set the measuring device to ohmmeter mode with a measurement limit of 50-100 Ohms and attach each probe of the device to the slip rings. The needle (or numbers will appear) of the multimeter will deviate to 2-5 ohms. If it is higher, then this is a sign of unreliable contact between the rings (poor soldering of the winding leads is possible). With lower resistance, interturn short circuit of the windings is obvious.
To be sure of the condition of the rotor, it is worth carrying out another check. A voltage of 12 volts from the battery should be supplied to the slip rings; connect the tester to the gap in the negative or positive wire, setting it to current measurement mode (observe the polarity of connecting the probes of the device). Its value should be in the range of 3-4.5 A. A higher current strength indicates an interturn short circuit of the windings. You can also determine if they are inoperable purely visually: this will tell you dark color wires and a burning smell.
Insulation resistance test
You will need 220 volts and a lamp designed for this voltage. Connect one wire to any slip ring, the second to the rotor body. If the winding is intact and open, the light will not light. If you observe its burning or even a slightly weak glow, the winding will have to be repaired (rewinded in a specialized workshop) or replaced.
Checking stator windings
This procedure also requires dismantling the generator and then disassembling it. This part of the device has several windings, so you will have to check each one. First, disconnect the wires leading from the diode bridge to the windings (you may need a soldering iron). After:
- Switch the measuring device to ohmmeter mode, to the minimum limit - usually 1 (whichever is better) or 10 ohms. It is recommended to carry out all measurements using a more accurate digital device.
- Connect the tester probes one by one to the terminals of the windings. The device should “produce” almost 0.2 Ohm.
- Test the resistance between one of the coil terminals and the “zero” (common wire) of the stator. The normal tester reading is 0.3 Ohm.
- Also check the integrity of the insulation. Connect one wire, connected to a 220 V household outlet, to the rotor body, the second - through a regular 25-40 W filament lamp, connected in series, to the winding terminal. If the latter has no defects (the insulation is not broken), the lamp will not light up.
At the same time, carefully inspect the “insides” of the stator and rotor: no traces of contact are allowed here. If they are present, this indicates wear of the bearings or bushings, which is confirmed by the “abnormal” noise made by the generator when the engine is running. By the way, if this is the case, this may be a sign of several malfunctions at once.
Checking generator brushes and slip rings
Their performance is determined visually. The minimum length of these products is 4.5 mm (new ones are 8-10 mm). The main reason for brush failure is their long-term use. Sometimes they quickly wear out and even break due to misalignment of the rotor shaft, which is associated with a manufacturing defect or deformation of the device due, for example, to an accident. The brush assembly is most often structurally combined with a voltage relay, so removal of this unit is possible without dismantling the generator. But you will have to buy the entire unit assembled: relay-regulator and brush holder.
The diameter of the new slip rings is 14.2-14.4 mm. A minimum value of 12.8 mm is allowed. These products can be freely purchased at auto stores.
To replace, unsolder the contact wires from the winding and remove the rings with a puller. New ones can be sanded on a lathe before installation: this will eliminate beating associated with surface unevenness and eliminate burrs.
Generator bearing wear
To replace them, the generator must be removed from the machine and disassembled as described below:
- remove the back cover (usually it is made of plastic) by releasing the clips or removing the screws;
- disconnect the brush assembly combined with the relay regulator;
- remove the diode bridge by unscrewing 3 screws;
- remove the metal back cover located under the plastic one and pull out the stator;
- pull out the rotor and clamp it in a vice to remove the pulley, having first unscrewed the nut securing it to the shaft;
- Remove the front cover along with the bearing: according to the manufacturer, it should be replaced as an assembly.
If you decide to replace the bearing separately, take an electric drill with a drill with a diameter of 4 mm and drill the cover at the core points. Knock out the old bearing, insert a new one and seal it. It is easier to remove the rear bearing: just use a puller with two legs. For some car models, the generator is non-removable: stator winding soldered to the lid. Then you will have to solder the wires to remove the stator. When choosing a bearing, you should pay attention to the fact that their cost is usually lower, and the quality may not be inferior to the original.
It often happens that the generator stops functioning only when the engine is warm. This phenomenon is due to the natural expansion of the metal with increasing temperature or a change in the properties of semiconductors (diodes) for the same reason. In this case, you should first check the functionality of the generator on a warm car, and if this does not bring results, then dismantle the device and check it after heating it with a hair dryer. In conclusion, it is worth noting that self-replacement such components of the generator as stator or rotor windings, bearings in domestic conditions is advisable only if you have the appropriate equipment, tools, and experience. If it is not there, then if the battery is not charging, limit yourself to trying to replace the relay-regulator combined with the brush assembly. To do this, you don’t have to buy a new device: you can install a known good one and evaluate the result.