A car generator is the main source of energy in the on-board network, and if it fails or fails, you won’t be able to drive for a long time on one battery. That is why it is so important to monitor the performance of the generator.
The full range of generator checks includes:
In most cases, it will not be difficult to check the car's generator with your own hands, because no matter what car you check, the principle is the same. But still, many car owners often wonder: how to check the generator with a multimeter or improvised means?
How to check the generator without removing it from the car
There are two ways, using a multimeter and without it at all. The first, relatively new, is to, and the second, old and proven, is almost the opposite - the battery terminal must be removed with the engine running.
- Checking the battery with a multimeter first happens at rest - the voltage should be in the range of 12.5-12.8 V. Then you need to measure the readings already on the running engine, if 13.5-14.5 V is observed at 2 thousand revolutions, then everything is in order. Moreover, on new cars, even 14.8 V is quite normal, as the manufacturers assure - the abundance of electronics affects. In conclusion, it remains check voltage under load, that is, by connecting consumers - a stove, headlights, heating, a radio tape recorder. A failure within 13.7–14.0 V is considered acceptable, but 12.8–13 V is already talking about a malfunction.
- The second method, like many "grandfather" ones, is simple and trouble-free, but at the same time quite dangerous and requiring care. According to allegations, it works both on VAZs and on relatively new cars, like the Aveo. What is the point - loosen the bolt of the negative terminal of the battery with a 10 key, start the engine and give a small load, turning on one of the consumers, for example, headlights. Then remove the terminal with the engine running - if it does not stall and the headlights do not fade, then everything is fine with the generator, otherwise you can be sure that it is broken. You should try this method at your own risk.
It is highly undesirable to allow the generator to operate when consumers are disconnected, especially the battery. This can lead to a malfunction of the relay controller.
Having found out that there is a malfunction, you should dismantle and check the removed generator with a multimeter, a light bulb and visually. Each of its elements is subject to verification separately.
| List of Generator Parts and Test Methods Applicable to Them | Visual check | Checking with a multimeter | Light bulb test |
|---|---|---|---|
| brushes | |||
| slip rings | |||
| Diode bridge | |||
| Voltage regulator | |||
| stator | |||
| Rotor |
The first step is to make sure that the alternator belt is well tensioned and the bearings are not broken. Extraneous noise and a very hot alternator indicate bearing wear.
How to check brushes and slip rings
To begin with, rings and brushes are visually inspected, and their condition is assessed. For example, the minimum balance is measured (min. height of collector brushes not less than 4.5 mm, and the min diameter of the rings is 12.8 mm). In addition, they look at the presence of workings and furrows.
Brushes removed from regulator brush assembly
Alternator rotor slip rings
How to check a diode bridge (rectifier)
Diodes are checked by measuring resistance and detecting conductivity. Since the diode bridge consists of two plates, we immediately check one and then the other. The tester should show diode conduction in only one direction. Now a little more: we hold one tester probe on the “+” terminal, and with the other we check the diode leads one by one, and then we swap the probes (in one case there should be a lot of resistance, but not in the other). Then, in exactly the same way, we proceed with the other part of the bridge.
It should be noted that the resistance should not be zero, as this indicates that the diode is broken. Broken bridge diode and when there is no resistance in both sides.
Checking the diode bridge
Checking slip rings
At least one a bad diode leads to failure of the entire diode bridge and gives the battery an undercharge.
The operation of the car often presents various surprises. Devices that we did not even think about working may fail. It is always necessary to monitor the main units and monitor their condition in order to be able to prevent an unpleasant breakdown in the middle of the road. If you think that buying an expensive European car will save you from having to check the operation of various components, you are mistaken.
One of the most delicate and difficult to repair units in the design of a car is a generator. This node performs the important task of energy recovery, which allows you to switch the operation of all electrical appliances from the battery directly to the generator. Thanks to the correct functioning of this unit, we can use the battery for five to seven years, only recharging it a few times.
The simplest methods for checking generator malfunctions
Let's start with very simple troubleshooting options. If you have an expensive modern car, always look at the on-board computer messages while starting the engine. An error code message may appear on the screen for a few seconds to help you identify any malfunctions in the generator system.
The error code must be reported to the service center or information found on the Internet, which will help you find out the cause of the breakdown with accuracy to the smallest detail. If the car just asks to go for diagnostics, you must definitely do this, and not guess what the problem might be. The simplest and most effective methods for testing a generator are as follows:
- start the car and turn on the headlights, music, air conditioning and other electrical appliances, open the hood and listen to the generator;
- with the car running and the high or low beam headlights on, press the gas pedal several times, notice if the light intensity changes;
- after a sufficiently large load on the generator (for example, a long trip in the evening), try the body of the device with your hand - it should not be too hot;
- listen to the generator at idle - it should not make extraneous sounds, whistles and squeaks;
- look in the dark at a working generator - if there are any sparks and other light accompaniments of work in it.
To safely test the generator while it is running, make sure that no sleeves or other pieces of clothing are hanging loose and cannot be caught by the device. Otherwise, you will have a hard time, because it will be difficult to release clothes from the engagement of the belt. It is better to avoid such moments, which will ensure your safety.
This generator check is an approximation and will not give you accurate data. But if you determine that there are signs of a malfunction in the device, it will be possible to quickly make the necessary repairs at the service station. After all, otherwise you may not know that the generator is the cause of all the problems in the operation of your car.
A more detailed and accurate test of the generator in the car
Another test method, which can only be tested on domestic cars and foreign cars before 1998, will help you understand if the generator is working. Start the engine and let it warm up to normal operation. Then remove the negative terminal from the battery. If the engine stalls, then the alternator is faulty.
This method of verification makes it easy to obtain data on the operation of the generator. True, the answer will be quite simple - either the device works or it does not work. That is, if you find out that the generator is not working, you will have to go to the service station to determine the specific cause of the breakdown. You can’t do this in new cars, because several serious problems can happen:
- the generator can simply fail if the charge sent to the battery by it does not reach its destination;
- the voltage regulator may also break, the replacement of which will cost you a fairly large amount;
- the computer can simply block the system, the engine will stall when the terminal is disconnected, but will not show a generator failure;
- the actions of the electronic engine management system under such circumstances can be generally unpredictable;
- after such a shutdown of the power unit, it may not be easy to restart it.
So it is better to refuse such a verification method if you have a new generation car at your disposal. Even new domestic cars will not be grateful to you for this way of testing the operation of the generator. But there are several more options for checking this device. You can use a voltmeter or meltimeter to measure the voltage at the output of the generator.
To do this, you need to get a voltage measuring device, as well as open the car's operating instructions on the page describing the operation of the generator. There are numerical voltage data and contacts that must be measured with a voltmeter. This verification method is the most reliable, but rather difficult to perform, because you need to measure a working generator.
Servicing a generator
To get answers to all questions and stop the problems of the car in the field of the electrical system, you need to contact a specialized master. This may be an official service station or a specialist who repairs the alternators of your brand of car. The main thing is that the person has a decent qualification and enough knowledge about the operation of the generator in your car model. The main advantages of such a service for the car owner are as follows:
- there are no risks of accidental breakdown of other vehicle components during inept checks;
- obtaining reliable results that are confirmed by a professional;
- the ability to quickly fix problems with the help of a specialist;
- performing only those work that will lead to the correction of problems, no spraying;
- high-quality diagnostics of the entire electrical system and the detection of the most obvious problems.
With the help of a specialist, you can fully adjust the operation of your car, forget about possible troubles and problems. A professional service will help you get the most out of your vehicle. You just need to choose a specialist who is really well versed in your equipment and can provide professional repair services. Such a master will allow you to get a working car within a few hours after being handed over for repairs.
We offer a visual look at the procedure for checking the generator using a voltmeter:
Summing up
One of the most important moments in the operation of the car is the correct functioning of all systems. It is imperative to use the possibilities of high-quality and reliable operation of the generator, as well as monitor possible malfunctions. If it seems to you that the generator is not working properly, and the on-board computer constantly gives out some kind of errors, you should go to the service and solve this problem. Otherwise, at one terrible moment, the car may simply stop in the middle of the road.
With the help of high-quality repairs, you can easily restore the performance of the car and get the maximum reliability that every driver expects from his vehicle. If you have experienced alternator failure, please describe the symptoms of these problems on your car model below in the comments.
Hello, dear motorists! You are welcomed on the pages of your blog by its author and creator -. Many drivers strive to learn how to service the “iron horse” on their own - this is not only cheaper than in a car or in a car service, but also informative from a practical point of view. Therefore, today I want to talk with you about how to check the generator and what this may require.
The need for verification is also caused by the fact that power surges are detrimental to modern electronics. Cars are literally stuffed with it, and any jump threatens to fail. It is the generator that is responsible for supplying voltage, including, it is responsible for powering electrical appliances on board the car, as well as for. If it is faulty, for example, it does not produce the required voltage, then we will not be able to go far. That is why many motorists are eager to learn about the methods and procedure for checking. Let's consider this mechanism in more detail.
Two main ways to check
So, let's start with the simplest method that does not require stands or other special equipment. For him, we just need a device called a "multimeter", although you can even do without it, but more on that below. First, we take measurements at rest - the indicators should be at the level of 12.5–12.8 Volts (as you understand, we are talking about voltage).
Then we check the health of the generator with the engine running. We bring the speed to 2000 - the voltage, if it is normal, should be in the range of 13.5–14.5 Volts or even a little more. If, when the current consumers (tape recorder, lighting, etc.) are turned on, the indicator does not fall below 13.7–14, then the generator is functioning normally.
There is another version of the test, which was used by our ancestors. First loosen the negative battery terminal. Start the engine and turn on the headlights. Now you need to remove the negative terminal (it is important not to confuse here, because the battery may be). If the lighting has not faded and the engine has not stalled, we can talk about the health of the node. Otherwise, you will have to dismantle it and check each part separately.
Generator components
These include the following elements:
- brushes;
- diode bridge;
- rotor and stator;
- anchor;
- relay-regulator
First, it is advised to check the belt tension. If required, then it is changed or tightened tighter. The presence of extraneous sounds can also indicate bearing wear. Then we remove the brushes and make their visual inspection. The minimum height must be at least 4.5 mm.
Check diodes, relays, etc.
Diodes are tested by measuring their resistance and current conductivity. To do this, we place one of the probes of the tester on the positive terminal of the battery, and measure the leads of the diodes with the other. In this way we pass the entire diode bridge. If the diode fails, then the resistance will be zero in both directions.
In the event that the battery is under- or overcharged, the voltage regulator should be checked. It is measured at the moment when the engine is "at speed" of 2000 and above. The regulator brushes deserve special attention - a 12-volt light bulb is used to check them. Instead of the expression "voltage regulator" you can find a relay-regulator (it's the same thing).
It is also necessary to check the stator, rotor and winding. If the generator hums strongly during operation, then the winding may “short”. Again we pick up our multimeter and measure the resistance between the contact rings of the rotor. The indicator should be in the range from 2.3 to 5 ohms. If it is below the minimum value, then the circuit occurs between the turns. High indicates an open or weak contact.
It is the stator that is one of the most complex parts of the generator, and without dismantling the entire assembly, we will not be able to check it. First of all, pay attention to the absence of traces of breakage and / or burnt contacts.
The work of checking the health of the generator may well be done in the garage on its own using only a multimeter. If we are talking about malfunctions, then it is necessary to dismantle the assembly with a sequential check of all components, as I wrote about this above. It is enough to observe the control lamp, check how tight the belt is and periodically clean the contacts. In this case, your generator will serve faithfully. On that note, we say goodbye. See you in the next episodes!
Good afternoon. In today's article I will tell you how to check the generator on a car without removing it. Traditionally for our site, the article contains a lot of photo and video materials.
How does a generator work and why is it needed?
In modern cars, there are many consumers of electricity - from car radio to. For the operation of all these consumers, electrical energy is needed. Its main supplier is the generator. When it cannot cover all needs, for example in a traffic jam, the energy stored in the battery is consumed. After conditions are met, the generator replenishes the battery charge.
At the slightest malfunction of the generator, there may be problems with replenishing the battery charge and, as a result.
You can clearly see the principle of the generator in this video:
How to check the electrical part of the generator?
This is done with a special device - a multimeter. It is sold in any hardware store and costs 500-700 rubles, or you can order it directly in China, and it will cost, without trade margins, 300-350 rubles.
The verification scheme is as follows:
We turn on the multimeter in the voltage measurement mode up to 20 volts DC.
We fix its probes on the wheels of the generator, with a fully charged battery, the device will show 12.5-12.9 volts.
We start the engine, and let it run at high speed for 4-5 minutes.
If the generator is working, the voltage will rise to 14.5-14.7 volts.
We gradually turn on consumers (headlights, interior heater, glass heating, music, seat heating) and control the voltage. Even at idle, it should not be lower than 13.5 volts.
If so, your alternator is good.
Here is a video of checking the generator with a multimeter:
If you do not have a multimeter, then the generator can be checked without it, but the accuracy of such a check is not high.
This is done as follows:
- Loosen the negative terminal on the battery.
- We start the engine, let it run, so that the idle speed decreases.
- Remove the negative terminal from the battery.
If the engine does not stall, the generator can be considered serviceable. “Gasing” with the terminal removed is unacceptable!
Here is an example video of removing the battery from a car with the engine running:
Important notes.
Many cars are equipped with a voltmeter, but its readings can be trusted very conditionally, since the accuracy of its readings is not great and often differs by 0.5-1 volts in any direction.
Checking the generator by removing the terminal is not always acceptable - not everywhere there is good access to the battery, but on complex cars, such a check is fraught with errors and the ignition of a warning lamp, check the engine.
Deal- it is safer to check the electrical part of the generator with a multimeter, measuring the voltage on the battery. In extreme cases, it is permissible to check the generator by throwing off the negative terminal.
How to check the freewheel without removing the alternator belt?
About the appointment and verification of the overrunning clutch on our website, therefore, briefly.
When the engine is running, the overrunning clutch should not creak or make noise.
With the engine turned off, use a thin screwdriver to turn the generator armature.
Ideally, it should scroll in one direction and sideways in the other. Here is a visual video for you:
If the overrunning clutch jams, the alternator belt, with extreme wear, may simply come off.
How to check alternator bearings?
In a good way, to check the bearings, it is necessary to remove the alternator belt. This is the only way to fully check the play and noise of the bearings.
There is an old-fashioned method of listening to bearings.
You will need a metal bar of sufficient length.
With the engine running, we rest the bar against the generator, and bring the other end to the ear (ATTENTION, you can’t put the bar in your ear, you will hear everything clearly anyway).
It's done like this:
Conclusion.
I hope that after reading this article, you understand how to check the generator on a car without removing it.
Brief algorithm:
- started the engine, threw off the negative terminal, the engine did not stall - OK
- heard that the bearings are not noisy - OK
- if the generator is equipped with a freewheel, checked it - OK
If all these points are fulfilled, the generator can be considered serviceable.
That's all I have today. If you have any questions or want to supplement the article, write comments.
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 a donor battery to start the engine, 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 the 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 probe 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 spot-welded to ensure reliable contact at different temperature conditions.
The car's alternator is an important part of the car's electrical equipment. At the first manifestation of signs of inoperability, it is necessary to check it with a multimeter.