An alternator check may be required when the battery warning light on the instrument panel comes on, which means that the battery has lost charge. It is useful for each driver to know how to check the generator and its parts, which will be described in detail in this article.
The lack of battery charge can occur not only due to the fault of the generator, but, for example, due to the failure of the regulator relay. And before checking the generator, you should first make sure that the regulator relay is working.
I wrote in detail how to check the health of various types of regulator relays here. And you can read about the device of the generator and its main malfunctions. The generator and the health of some of its parts can be checked without disassembling the generator or with disassembly, and the verification methods will be described below.
If, during the check, any malfunctions of the generator are revealed, then they can be eliminated as described here in, about the repair of the generator.
Checking the generator in parts.
Stator check generator. The generator stator is checked separately after generator disassembly. All stator leads must be disconnected from the diodes (valves) of the rectifier unit.
First, visually make sure that the varnish insulation of the stator winding wires does not show signs of overheating (and even more so melting), which can occur during a short circuit in the rectifier valves. The stator with traces of insulation melting should be replaced.
Checking the generator using a stand .
Testing on the bench allows you to most accurately determine the health of the generator and the compliance of its characteristics with the nominal ones. To assemble the stand, you will need to fix the electric motor with a pulley on a welded frame from a corner (or a profile pipe), then fix the generator on the same frame so that the electric motor pulley rotates the generator pulley with a belt.
You will also need a rheostat 4 (see the connection diagram on the left) a voltmeter 3, a 12-volt control light (3 W) 1, an ammeter 5, a switch 6, and a car 7 (the generator itself is numbered 2 in the figure). Everything is connected according to the diagram in the figure.
Before checking the generator, the contact rings of the generator should be cleaned of plaque, and the brushes should be well ground in shape to the contact rings. After connecting all the components of the stand according to the figure, we turn on the electric motor and set the voltage at the generator output to 13 volts with rheostat 4. Then we bring the generator rotor speed to 5000 rpm.
At these speeds, let the generator run for at least two minutes, then measure the recoil current. A serviceable front-wheel drive VAZ generator (VAZ 2108 - 09) must have a current of at least 55 amperes. For more powerful generators of foreign cars, of course, the recoil current is greater, and how many amperes exactly - this can be clarified in the technical specifications of a particular generator.
1 - generator, 2 - voltmeter, 3 - control light, 4 - rheostat, 5 - ammeter, 6 - switch, 7 - battery.
The wall for checking the generators of foreign cars is almost the same, only the outputs of imported generators have other designations (D and B +), as in the figure just above.
If it turns out that the current strength is less than expected, then this indicates a malfunction in the stator or rotor winding of the generator, or damage to the diodes, or wear of slip rings or brushes. In this case, it will be necessary to disassemble and check the windings and diodes, as described above.
Checking the voltage at the generator output is checked at a rotor speed of 5000 rpm. At the same time, we set the recoil current to 15 amperes with a rheostat and measure the voltage at the generator output. It should be 14.1 ± 0.5 volts, at a temperature of 25 ± 10 ° in the room where the stand is located.
If the voltage has a different value (less or more than 14.1 ± 0.5 volts), then the regulator relay should be replaced with a new one or a known good one and repeat the test again. If replacing the relay does not help and the voltage will still differ from the norm, then the problem is not in the regulator relay, but in the stator or rotor windings, or in the faulty diodes of the rectifier unit.
Checking the generator with an electronic oscilloscope .
Not everyone has an electronic oscilloscope, but it allows you to quickly and accurately check the health of the generator and determine the nature of the damage by the shape of the rectified voltage curve. Therefore, it makes sense to write such a way to check the generator.
To check, you should assemble the circuit, as shown in the figure on the left. Then we disconnect the wire of the common output of three additional diodes from terminal B of the voltage regulator relay and wrap the tip of the disconnected wire with electrical tape (so that it does not short on the generator case).
Next, we connect the wire from the battery to terminal B (see figure) through control light 1. Now the excitation winding will be powered only from the battery. We turn on the electric motor of the stand and achieve the rotation of the generator rotor at about 1500 - 2000 rpm. Then, with switch 6, we disconnect the battery from terminal 30 of the generator and, using rheostat 4, we achieve a recoil current of 10 amperes.
We check the voltage at terminal 30 of the generator on the oscilloscope. With good rectifier diodes and a good stator winding, the rectified voltage curve has the shape of uniform saw teeth as in Figure A (see the figure just below).
And the alternator is OK.
B - the diode is broken.
B - open circuit in the diode circuit or in the stator winding.
If there is an open or short circuit in the rectifier diodes or an open in the stator winding, then the shape of the curve will be with uneven teeth with deep cavities (see Figure B and C).
When terminal 30 has been checked and the curve shape is normal, check the voltage at plug 61 or at the wire end that is disconnected from plug B of the regulator relay. These points are the common output of three additional diodes that feed the excitation winding when the generator is running.
Here too, the shape of the stress curve must have the correct shape of the teeth. If the shape of the curve has an irregular shape of the teeth, then this indicates the failure of additional diodes.
You can read more about checking and restoring the generator and the regulator relay of a foreign car.
And finally, a few warnings that are important for every driver to know.
- The negative cable from the battery must always be connected to ground, and the positive cable connected to terminal 30 of the generator. Reverse (erroneous) connection of the battery will instantly cause increased current through the generator rectifier diodes and the diodes will fail.
- The generator must not be allowed to operate with the battery disconnected, as this will cause short-term overvoltages at terminal 30 of the generator and this will damage the voltage regulator relay and other electronic devices of the on-board network of a modern car.
- It is strictly forbidden to check the health of the generator for a spark, even by briefly connecting terminal 30 of the generator to ground. In this case, a large current flows through the diodes of the rectifier unit and they fail. You can only check the performance of the generator using a voltmeter and ammeter.
- The generator rectifier diodes cannot be checked with a megohmmeter (it has too much voltage for diodes) or with a voltage of more than 12 volts. Since the diodes will be broken during such a check (a short circuit will occur).
- It is also forbidden to check the electrical wiring of the machine with a megger or a lamp powered by a voltage of more than 12 volts. If such wiring is necessary, then you must first disconnect the wires from the generator terminals.
- It is possible to check the insulation resistance of the generator stator winding with increased voltage only at the stand, but always with the phase winding leads disconnected from the rectifier.
- When bodywork using electric welding, be sure to disconnect the wires from all terminals of the generator and battery.
That seems to be all. Of course, checking the generator is not such a simple matter, but with a competent approach and the availability of appropriate knowledge, it is quite possible to identify any malfunction and fix it without the help of an auto electrician, success to everyone.
The main source of power in the car is the generator, it is such a "mini-power plant". Incorrect or unstable operation of this node is fraught with bad (battery). A failed generator does not provide charging, therefore, the on-board network of the car will work on a battery that will not last for a long time. As a result, the battery is completely discharged, the engine "stalls" somewhere outside the city, and you have a new "headache" and the need to replace the generator.
In order to prevent such a scenario, it is necessary to regularly monitor the status of this device, as well as the charging it gives. If you notice any interruptions in work, you need to check the generator, and you will now learn how to do this.
But before that, I consider it necessary to talk about precautions and certain rules that must be observed when checking this electrical appliance in order not to damage it.
!!! It is forbidden:
- Check the performance of the generator by short circuit, that is, "to a spark."
- Connect terminal 30 (in some cases B+) to ground or terminal 67 (in some cases D+).
- Allow the generator to work without consumers turned on, it is especially undesirable to work with the battery disconnected.
- Carry out welding work on the car body with the wires of the generator and battery connected.
- !!! Important:
- Checking is done with a voltmeter or ammeter.
- Checking the valves is carried out with a voltage not higher than 12 V.
- In the case of replacing the wiring of the electric generator, it is necessary to select wires of the same cross section and length.
- Before checking the device, make sure that all connections are working and that the drive belt is properly tensioned. A belt is considered correctly tensioned, which, when pressed on the middle with a force of 10 kg / s, bends by no more than 10-15 mm.
How to check the generator with a multimeter or voltmeter?
Checking the voltage regulator
- In order to check the voltage regulator, you will need a voltmeter with a scale from 0 to 15 V. Before starting the test, warm up the engine for 15 minutes at medium speed with the headlights on.
- Measure the voltage between the terminals of the "mass" of the generator and "30" ("B+"). The voltmeter should show normal voltage for the particular vehicle. For example, for a VAZ 2108, it will correspond to - 13.5–14.6 V. If the voltage is lower or higher, most likely the regulator needs to be replaced.
- In addition, you can check the regulated voltage by connecting a voltmeter to the terminals. It should be noted that the result of such a measurement will not be accurate if you are sure that the wiring is 100% correct. In this case, the motor should operate at medium speeds close to those with the headlights on and other consumers of electricity. The voltage size must match a certain value for a particular car model.
Checking the diode bridge of the generator
- Turn on the voltmeter in the AC measurement mode and connect it to the "ground" and terminal "30" ("B+"). The voltage should be no more than 0.5 V, otherwise there is a possibility of diode failure.
- To check the breakdown to "ground", it is necessary to disconnect the battery, as well as remove the generator wire that goes to the "30" ("B+") terminal.
- Then connect the device between terminal "30" ("B+") and the disconnected wire of the generator. If the discharge current on the device exceeds -0.5 mA, it can be assumed that there is a breakdown of the diodes or the insulation of the generator diode windings.
- The recoil current strength is checked using a special probe, which is an addition to the multimeter. It is something like a clamp or tongs, which covers the wires, thus measuring the strength of the current that passes through the wire.
Checking the recoil current
- To measure the recoil current, you need to cover the wire with the probe, which goes to the terminal "30" ("B+").
- Then, start the engine and take a measurement, during the measurement, the engine should run at high speeds. Turn on electrical appliances in turn and take measurements for each consumer separately.
- Then count the readings.
- The following test must be carried out with all power consumers switched on at the same time. The measurement value should not be lower than the sum of the readings of each of the consumers, when you measured each of them in turn, a discrepancy of 5 A downwards is allowed.
Checking the generator excitation current
- To check the excitation current of the generator, start the engine and give it high speed.
- Place the measuring probe around the wire connected to terminal 67 (“D +”), the readings on the device will correspond to the value of the excitation current, on a working generator it will be equal to - 3-7 A.
To check the excitation windings, you will need to remove the brush holder and voltage regulator. It may be necessary to clean the slip rings, also check for breaks in the winding or shorts to ground.
Sometimes a motorist faces the question of checking the generator of his car. After all, it is very important to prevent and eliminate possible malfunctions in time, which can 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 and, most importantly, 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, experimenting in this way, you can notice that the voltage is kept within 14-14.2 Volts, then we can safely say that everything is in order with the generator and the 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 in conditions, it is worth checking the rotor. To do this, you need to find out what is the resistance between the slip rings of the stator. If these figures do not exceed 5-10 ohms, then everything is in order, if this figure is higher - perhaps somewhere there was a break in the windings. 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.
Checking the diode bridge is easy. As you know, it consists of 6 - three positive and three negative. It is necessary to disconnect all the leads from the plates with diodes and conduct a test: attach the probes to the diode leads, and then repeat the experiment, swapping them. In one position, a beep should be heard, and in the other not. If a squeak is heard in both directions, we are talking about a hole in the diode, which means it will have to be changed. But without sufficient experience, this is difficult to do, so you have to change the entire diode plate.
The stator must be carefully examined - there should not be any burning or damage to the winding. After you need to ring the winding with a multimeter. As for the bearings, nothing should interfere with their free rotation: there should be no noise and play. The brushes should protrude from the edges by only 5 mm. Chips, jamming and backlash are excluded. If there are any deviations, it is better to replace.
The constant undercharging of the battery or its absolute discharge at the most inopportune moment is a headache for many car owners. One source of these problems could be the alternator. But how to check it? Maybe it's not about him at all? Let's figure it out together how much the generator should produce for the normal functioning of all car systems and maintaining the battery in a charged state.
The battery in the car is an important element of the system, which is responsible for providing the on-board network of the car with electricity. The generator is used to charge the battery while it is active. Unstable operation of a device that generates electricity causes a voltage drop in the network and a lack of restoration of the power source capacity.
The normal performance of the generator is understood as the timely and full replenishment of the battery charge level, which decreases under load. Checking the amount of battery charge from the generator is simple and can be done by the car owner on their own.
Diagnostics of an automotive energy generating device includes a visual inspection of the unit, its elements and related parts, as well as the measurement of voltage and current. At least twice a year, the tension of the drive belt should be checked, excessive loosening of which leads to a decrease in the performance of the generator, and sometimes can lead to a breakdown of the device. Once a year, you can check the elements of equipment - fasteners, diode bridge, voltage regulator and others. Timely maintenance of the battery will also guarantee the absence of problems - cleaning the terminals, adding distilled water.
Diagnostics of indicators such as voltage, current, resistance is also required twice a year. For its implementation, you will need special devices - a voltmeter, multimeter or load plug.
How much charge should go to the battery from the generator
It is traditionally believed that 13.5-14.5V should be supplied by the generator to the battery and this is completely enough to make up for the cost of the battery.
It should be borne in mind that the use of a battery with more power than the manufacturer recommends in a car requires the installation of a more efficient generating device.
It is necessary to take into account the load that the generator must withstand - it is calculated according to the maximum performance of all electrical appliances and auto systems.
Do not forget that the charging current from the device that generates energy will allow you to start the car in the cold season. In order to avoid problems with the car factory, we recommend purchasing generating equipment, the charge current of which will be approximately 10% of the power source capacity. That is, for a battery of 100 A / h, a generator is needed that can produce 10A. Note that for many cars, 100 amp equipment will be pushed to its limit because the power consumption of the car system is around 80 amps. Therefore, the choice of a source that generates energy must take into account both the battery capacity and the consumption in the network.
How to check alternator voltage on battery
The potential difference can be diagnosed in two ways - directly on the generating equipment and through the battery. The generator is directly connected to the power source with a thick wire, therefore, to check the level of potential difference, you can measure the voltage at the power source. This will require special devices - a voltmeter, multimeter or load plug.
The wires of the first measuring instruments are connected to the battery in any sequence. The plug must be connected to the battery terminals with strict polarity. It is generally accepted that the normal voltage in the network should be at least 12 volts. At idle without turning on all the electrical devices of the car, this indicator should be at the level of 13.5-14V. A drop in voltage values to 13.3-13.8 volts is considered acceptable.
At the same time, conventional testing equipment can check the resistance of the generator elements - rotor, stator and diode bridge. Diagnostics of rotary equipment is carried out by its winding. It is necessary to connect the probes of the device with slip rings. If the multimeter gives readings from 2.3 to 5.1 ohms, then this element is working. The current consumption of the winding should be within 3-4.5 amperes.
Its normal resistance is 0.2 Ohm. The diode bridge is checked by the presence or absence of resistance, the indicators do not matter. The only thing worth considering is that there should not be a zero dimension. Measurements are carried out in pairs - positive exit and all plates on this side or minus and all elements.
We remind you that for normal charging of a car battery, the voltage supplied by the generator must be from 13.5 to 14 volts.
How many amps does a car alternator put out per battery
The current strength required by the electrical system of each car is individual and depends on the number of electricity consumers and their values. And also the charge current must be sufficient to charge the power supply.
It is worth noting that ampere readings appear only when there is a load in the car's electrical system and, accordingly, the battery is discharged. After starting the engine of the car, the charge current is about 6-10 amperes and drops over time, because the battery is charging, which takes on the main energy consumption. If you turn on additional equipment - headlights, radio or heated mirrors, you can see an increase in the charging current.
When buying a generator, pay attention to its technical characteristics, which the manufacturer indicates on the case - this is where you will find information about how much current will be supplied to the battery as much as possible.
In the table below, you can see the approximate values \u200b\u200bof the current strength that the generator shows at different loads.
Table 1. How many amps does the generator produce under load.
Signs of a malfunctioning generator
In modern cars, breakdowns in the electrical system are one of the most common. A large number of electronics obliges you to carefully monitor the operation and condition of the generator and battery, because their failure can immobilize the car. The most common signs of a generator failure are:
- light indication of the battery on the instrument panel;
- unstable operation of the battery (its boiling over or undercharging);
- different intensity of headlights;
- extraneous sounds from the generator.
If you notice incorrect operation of the car, then perhaps the battery charging current from the generator is insufficient.
All malfunctions of electrical equipment, to which the vehicle’s energy-generating device belongs, are mechanical (deformation or breakage of fasteners, housing, malfunction of bearings, clamping springs, drive belt, etc.) or electrical (winding breaks, malfunctions of the diode bridge, burnout or wear of brushes , short circuits between turns, breakdowns, etc.).
Don't write off a broken generator: find out if there are repair kits and spare parts. Replace them if possible. If you cannot carry out repairs yourself, then take the generator to a workshop. Many craftsmen will be able to restore the unit at no extra cost and in the shortest possible time.
However, individual breakdowns require the purchase of a new device that generates electricity. For example, a failing bearing that is soldered into the generator housing cannot be repaired or replaced in most cases.
Remember that the failure of this unit can be caused not only by wear and corrosion, but also by the poor quality of the elements and components; excessive load; external influence of salts, liquids, temperatures.
Other causes of low voltage
Not always a small potential difference in the system is associated with a breakdown of the generator or a bad battery. If the diagnostics of these elements did not reveal any problems, then you should pay attention to the following:
- the condition of the battery terminals - junction density and oxidation;
- wiring problems - oxidation, violation of its integrity;
- output contacts to electrical appliances;
- correctly selected energy consumers.
Each contact must be tightly adjoining and integral, that is, the absence of formations (for example, sulfation) that will interfere with the passage of current is necessary. Incorrect connection of the contacts leads to an accelerated discharge of the battery even when the car is not running.
To improve the connection of the elements of the electrical system of the car, it is necessary to strip all contacts and restore the integrity of the wires by replacing them or connecting and winding them with insulating tape.
In conclusion, I would like to repeat that the stable operation of the car requires constant monitoring of all elements, and the generator should attract special attention. The battery is charged from it and provides electricity to the entire automotive system. Pay attention to all the elements: generator brushes, slip rings, voltage regulator, equipment winding.
The most correct measurements should be taken when the battery is fully charged and in various modes. Remember that the manufacturer ties the characteristics of the generator to the number of engine revolutions - they help to generate a certain current.
Detailed video on how to check the generator:
Do you have experience diagnosing a generator and solving problems in a car's electrical system? Please share your experience and opinion with our readers in the comments. If you have questions about the topics covered, we will be happy to answer them.
Car electrical faults are very common and occupy one of the leading places in the list of breakdowns. They can be conditionally divided into malfunctions of current sources (batteries, generators) and consumer malfunctions (optics, ignition, climate, etc.). Main The vehicle's power sources are batteries and alternators.. The failure of each of them leads to a general malfunction of the car and its operation in abnormal modes, or even to immobilization of the car.
In the electrical equipment of a car, the battery and the alternator work in unbreakable tandem. If one fails, after a while the other will fail. For example, it leads to an increase in the charging current of the generator. And this entails a malfunction of the rectifier (diode bridge). In turn, when coming from the generator, the charging current may increase, which will inevitably lead to a systematic recharging of the battery, electrolyte “boiling away” and rapid destruction.
Common generator malfunctions:
- wear or damage to the pulley;
- wear of collector brushes;
- collector wear (slip rings);
- damage to the voltage regulator;
- short circuit of the turns of the stator winding;
- wear or destruction of the bearing;
- damage to the rectifier (diode bridge);
- damage to the wires of the charging circuit.
Common battery problems:
- short circuit of battery electrodes/plates;
- mechanical or chemical damage to the battery plates;
- violation of the tightness of battery cans - cracks in the battery case as a result of impacts or improper installation;
- chemical. The main causes of these malfunctions are:
- gross violations of the rules of operation;
- expiration of the service life of the product;
- various manufacturing defects.
Of course, the design of the generator is more complicated than the battery. It is quite reasonable that there are many times more generator malfunctions, and their diagnosis is much more difficult.
It is very useful for the driver to know main causes of generator malfunctions, ways to eliminate them, as well as preventive measures to prevent breakdowns.
All generators are divided into generators variable and direct current. Modern passenger vehicles are equipped with alternators with a built-in diode bridge (rectifier). The latter is necessary to convert current into direct current, on which the car's electrical consumers operate. The rectifier, as a rule, is located in the cover or housing of the generator and is one with the latter.
All electrical appliances of the car are designed for a strictly defined range of operating currents by voltage. As a rule, operating voltages are in the range of 13.8–14.7 V. Due to the fact that the generator is “tied” with a belt to the engine crankshaft, from different revolutions and vehicle speeds, it will work differently. It is for smoothing and regulating the output current that the relay-voltage regulator is intended, which plays the role of a stabilizer and prevents both surges and dips in the operating voltage. Modern generators are equipped with built-in integrated voltage regulators, colloquially referred to as "chocolate" or "pill".
It is already clear that any generator is a rather complex unit, extremely important for any car.
Types of generator malfunctions
Due to the fact that any generator is an electromechanical device, there will be two types of malfunctions, respectively - mechanical and electrical.
The former include the destruction of fasteners, the housing, the malfunction of bearings, clamping springs, belt drive, and other failures not related to the electrical part.
Electrical faults include winding breaks, diode bridge faults, brush burnout/wear, inter-turn short circuits, breakdowns, rotor beats, relay-regulator faults.
Often, symptoms indicating a characteristic faulty generator may also appear as a result of completely different problems. As an example, a bad contact in the alternator excitation circuit fuse socket will indicate a malfunction of the alternator. The same suspicion may arise due to burnt contacts in the ignition lock housing. Also, the constant burning of the lamp indicating a malfunction of the generator can be caused by a breakdown of the relay, the blinking of this lamp, which turns on, may indicate a malfunction of the generator.
The main symptoms of a malfunction of the oscillator:
- When the engine is running, the low battery warning lamp flashes (or stays on).
- Discharging or recharging (boiling away) of the battery.
- Dim car headlights, rattling or quiet sound signal when the engine is running.
- A significant change in the brightness of the headlights with an increase in the number of revolutions. This may be permissible with an increase in speed (resetting) from idle, but the headlights, having lit up brightly, should not increase their brightness further, remaining at the same intensity.
- Extraneous sounds (howling, squeaking) coming from the generator.
The tension and general condition of the drive belt must be checked regularly. Cracks and delaminations require immediate replacement.
Generator repair kits
To eliminate these malfunctions of the generator, it will be necessary to carry out repairs. Starting to search for a generator repair kit on the Internet, you should prepare for disappointment - the kits offered, as a rule, contain washers, bolts and nuts. And sometimes you can return the generator to working capacity only by replacing - brushes, a diode bridge, a regulator ... Therefore, a brave man who decides to repair makes an individual repair kit from those parts that fit his generator. It looks something like the table below, using the example of a pair of generators for the VAZ 2110 and Ford Focus 2.
Generator VAZ 2110 - KZATE 9402.3701-03 for 80 A. It is used on VAZ 2110-2112 and their modifications after 05.2004, as well as on VAZ-2170 Lada Priora and modifications
Generator Renault Logan - Bosch 0 986 041 850 for 98 A. Used on Renault: Megane, Scenic, Laguna, Sandero, Clio, Grand Scenic, Kangoo, and Dacia: Logan.
Troubleshooting
On modern cars, the use of the "old-fashioned" method by dropping the battery from the battery terminal can also lead to serious damage to many of the car's electronic systems. Significant voltage drops on the vehicle's on-board network can disable almost all on-board electronics. That is why modern generators are always checked only by measuring the voltage in the network or diagnosing the most removed node on a special stand. First, the voltage at the battery terminals is measured, the engine starts and readings are taken already with the engine running. Before starting, the voltage should be about 12 V, after starting - from 13.8 to 14.7 V. A deviation to a large side indicates that you are "recharging", which implies a malfunction of the relay-regulator, to a smaller one - that no current is flowing. The absence of charging current indicates generator malfunction or chains.
Causes of breakdowns
Common causes of generator malfunctions It's just wear and tear and corrosion. Almost all mechanical failures, whether it be worn brushes or collapsed bearings, are the result of long operation. Modern generators are equipped with closed (not serviced) bearings, which simply need to be replaced after a certain period or mileage of the car. The same applies to the electrical part - often the components must be replaced entirely.
Also, the reasons may be:
- low quality of manufacturing components;
- violation of the rules of operation or work outside the limits of normal modes;
- external factors (salt, liquids, heat, road chemicals, dirt).
Self test generator
The easiest way is to check the fuse. If it is serviceable, and its location. The free rotation of the rotor is checked, the integrity of the belt, wires, housing. If nothing raised suspicions, brushes and slip rings are checked. During operation, the brushes inevitably wear out, they can jam, warp, and the slip ring grooves become clogged with graphite dust. A clear sign of this is excessive sparking.
There are frequent cases of complete wear or breakage of both bearings and stator failure.
The most common mechanical problem in a generator is bearing wear. A sign of this malfunction is a howl or whistle during operation of the unit. Of course, the bearings must be replaced immediately after inspecting the seats. Weakening can also cause weak generator performance. One of the signs may be a high-pitched whistle from under the hood when the car is accelerating or accelerating.
To check the excitation winding of the rotor for short-circuited turns or breaks, you need to connect a multimeter switched to resistance measurement mode to both contact rings of the generator. Normal resistance is from 1.8 to 5 ohms. The reading below indicates the presence of a short circuit in the turns; above - a direct break in the winding.
To check the stator winding for "breakdown to ground", they must be disconnected from the rectifier unit. With the resistance readings given by the multimeter, which have an infinitely large value, there is no doubt that the stator windings are not in contact with the housing ("ground").
A multimeter is used to test the diodes in the rectifier unit (after completely disconnecting from the stator windings). The test mode is "diode test". The positive probe is connected to the plus or minus of the rectifier, and the negative probe is connected to the phase output. After that, the probes are interchanged. If at the same time the readings of the multimeter are very different from the previous ones, the diode is working, if they do not differ, it is faulty. Another sign indicating the imminent "death" of the diode bridge of the generator is the oxidation of the contacts, and the reason for this is overheating of the radiator.
Repair and Troubleshooting
All mechanical problems are eliminated by replacing faulty components and parts(brushes, belt, bearings, etc.) for new or serviceable ones. On older models of generators, slip rings are often required to be machined. Drive belts are replaced due to wear, maximum stretch or the end of their service life. Damaged rotor or stator windings, they are currently being replaced with new ones as an assembly. Rewinding, although it is found among the services of car repairmen, is less and less common - it is expensive and impractical.
And that's all electrical problems with a generator decide by checking like others circuit elements(in particular the battery), so and directly its details and output voltage. One of the most common problems car owners face is overcharge, or vice versa, generator low voltage. Checking and replacing the voltage regulator or diode bridge will help eliminate the first malfunction, and it will be a little more difficult to deal with the issuance of low voltage. There can be several reasons why the generator produces low voltage:
- increased load on the onboard network by consumers;
- breakdown of one of the diodes on the diode bridge;
- failure of the voltage regulator;
- V-ribbed belt slippage (due to low tension)
- poor ground wire contact on the generator;
- short circuit;
- squandered battery.