The generator is the main source of current that powers the vehicle's electrical appliances. Malfunction car generator entails insufficient charging of the battery, which leads to a drop in voltage, blackout and a complete stop of operation of electrical appliances. For this reason, it is necessary to regularly check the serviceability of the generator and immediately respond to problems in its operation.
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Various signs and symptoms may indicate decreased performance and failure of the generator. The main one is the appearance of noise of different nature emanating from the generator, the battery is insufficiently charged or completely discharged. If the battery is not sufficiently charged, the car either cannot be started, or the engine may stall after some time of operation. This may also indicate that the battery has reached the end of its useful life.
Signs of mechanical damage to the generator
The presence of mechanical damage to the generator can be determined by the nature of the sounds it makes during operation. It can be creaks, whistles, rattling, howling, knocking. More often the problem in this case is wear or insufficient lubrication of the bearings. If, after changing the lubricant, suspicious noises do not disappear, you may need to complete replacement bearings.
The presence of extraneous noise can also be a consequence of an interturn short circuit in the stator winding. In a similar way, a malfunction of connections and contacts, a short circuit of the winding to the housing, manifests itself. All this indicates problems with the interaction of parts during generator operation. They can be identified by visual inspection mechanisms. At the same time, it is easy to detect unwanted winding short circuits, bad contacts and connections. Depending on the extent of the detected malfunctions, you can decide whether to fix them yourself or seek help from specialists.
Car generator voltage diagnostics
The reasons for the malfunction of the generator may lie not only in mechanical damage to its parts. To detect them, you should also check its output voltage. For this purpose, it is necessary to use electrical measuring instruments. Sometimes ohmmeters or multifunctional testers - multimeters - are used for this.
However, most often it is enough to use a voltmeter. It must be connected to the terminals of different poles of the battery and the car engine must be started.
The voltage at the battery terminals when starting the engine should not be less than 8 Volts. In this case, the accuracy of measurements will be higher if they are carried out at environment temperature from +20 C and already warmed up car engine.
After fixing the indicators when starting the engine, you should gradually increase its speed to 3000 per minute. When such a load is reached, the voltmeter readings must be taken into account again. Recording measurements of less than 12.5 Volts will indicate a malfunction of the generator and the need for its repair.
The faulty generator must be dismantled by first disconnecting it from the battery terminals. Then you should unscrew the voltage regulator fastenings with a screwdriver. After this, carefully inspect and determine the degree of wear of the generator brushes, as well as its slip rings, and clean them if there is carbon deposits. Often the cause of generator failure is a faulty voltage regulator. Therefore, it must be periodically checked and changed if problems are detected.
After troubleshooting, a working generator is mounted in the reverse order of its dismantling. The final step of this process should be to carefully connect the ground.
After installing the generator, the voltage readings at the poles should be checked again battery. When the engine is running at 3000 rpm, they should vary from 13.5 to 14.5 volts. These values mean that the generator's functionality has been restored and it is in good working order.
Checking the voltage regulator
The next diagnostic stage will be checking voltage stabilization. To do this, turn on the car's high-beam headlights and use a voltmeter to measure the voltage at the battery poles. A deviation of values not exceeding 0.4 Volts from previous measurements when starting the engine indicates the serviceability of the generator. Deviations upward indicate unstable work generator, the search for the causes of its malfunction will have to continue.
Checking the vehicle's power supply circuits
Further search for the reasons for the loss of functionality of the generator consists of diagnosing the vehicle’s power supply circuits. For this purpose you will also need an electrical measuring device. With its help, you first need to check the diode bridge. In this case, the voltmeter is connected to the generator and ground terminals. Device values exceeding 0.5 Volts indicate a malfunction of the diodes. To determine their breakdown, you should connect a measuring device between terminal “30” and the disconnected connecting wire of the generator. An acceptable electric current strength of less than 5 mA is acceptable.
Then the voltage regulator is checked. The engine should be warmed up for about a quarter of an hour at medium speed. In this case, all vehicle lights must be turned on. The field of this is measured at ground and terminal “30”. The optimal performance of the device in this case may differ depending on the type and make of the car, which can be found out from its technical characteristics.
Also, the regulated voltage indicators depend on the modification of the car and its parameters, which can be measured by connecting the tester to the battery. This measurement is carried out at maximum engine speed with all electrical appliances of the car turned on.
The serviceability of the field winding is checked by measuring its resistance. To do this, you can use a multimeter or ohmmeter. At the beginning of this operation, the voltage regulator and brush holder are removed. The winding and its integrity are visually inspected, and if necessary, the slip rings are cleaned. The meter is connected to the rings. The optimal resistance of working parts should be from 5 to 10 ohms.
A multimeter is necessary when diagnosing a short to ground. To do this, put the tester in the “ringing” mode, touch the armature body with one probe, and the contact ring with the second. It's simple: if it doesn't ring, it's working, if it rings, it's faulty.
Conclusion
Guided by these recommendations, you can easily diagnose a car generator yourself. To do this, you will only need certain skills in using the simplest tools for dismantling and assembling, as well as using electrical measuring instruments. However, for a more accurate check and thorough diagnostics, you should contact certified car services, whose qualified specialists, using special equipment, will quickly identify and eliminate all problems with the generator.
Video: how to check the generator
The malfunction of the car generator is classified as critical, in which further operation vehicles not allowed. You can use a multimeter to check the functionality of the generator.
Signs of abnormal operation of a car generator may include:
- no “battery” indication on dashboard when the ignition is turned on;
- the “battery” light glows after starting the engine;
- periodic blinking of the “battery” signal indicator while driving;
- the smell of burnt electrical wiring in the generator area;
- failure to start the engine after parking.
Lack of battery charge with a faulty generator leads to problems with starting the engine. More dangerous is a malfunction associated with exceeding the current and voltage of the car battery charge. Many car enthusiasts use a donor battery to start the engine, after which they disconnect the battery terminals to switch to charging their own battery. At this moment, the vehicle's electrical equipment 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 breakdown of the protective zener diodes in the engine control unit. In this case, expensive repairs to the engine control unit are required.
Causes and possible consequences of the malfunction
The generator may not work for the following reasons:
- malfunction of the voltage regulator (“pills”, “chocolates” in the slang of car enthusiasts);
- wear (destruction) of brushes;
- short circuit of the exciting winding (rotor);
- breakdown of diodes (located in the horseshoe);
- wear of bearings and bushings.
A faulty voltage regulator usually results in a lack of battery charge. In this case, the “battery” indicator light appears on the dashboard. The engine continues to run until the battery is discharged to approximately 8 - 9 volts.
During daylight hours, the battery charge may be enough for 30-50 kilometers, provided that the battery was well charged at the time the malfunction occurred.
If the output stages of the voltage regulator breakdown, a malfunction may occur due to an increase in the generator output voltage to 17 - 20 Volts. This recharges the battery. The consequence of overcharging is the process of boiling of the electrolyte. If signs of corrosion appear under the hood in the battery area, it is necessary to check the generator.
A breakdown of the diode bridge can occur when the battery is accidentally reversed (installing the terminals in wrong polarity). Typically, diodes are punched in pairs in one arm. A faulty diode has a resistance close to zero. In this case, the stator winding of the generator operates in short circuit mode and becomes very hot.
After a few minutes of engine operation, the windings overheat, and a smell of burnt electrical wiring appears under the hood of the car. To avoid fire, the engine must be turned off and the generator checked.
Wear of the brushes leads to gradual failure of the generator. First, while driving, the charge indicator light on the dashboard begins to blink, then it begins to glow constantly. In many generator models, the brushes are changed together with the voltage regulator.
A short circuit in the generator windings can lead to a significant change in output parameters and overheating of the device.
Initial check sequence
An initial performance check can be performed 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 terminal. After this, you need to start the engine and let it reach stable mode. idle speed. 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 charging process either does not occur at all, or the charging current is extremely small. The generator is operating in abnormal mode. When the voltage is more than 14.8 Volts, the battery is overcharged. This can lead to boiling of the electrolyte, an increase in acid concentration, and destruction of the battery plates.
To check the voltage at the generator output, you need to turn on the car lamp in the open circuit from terminal 30 on the generator (the point of contact with the thick wire leading to the positive terminal of the battery or starter).
Next, connect the multimeter in the “=20V” mode with the red probe to contact 30 of the generator, and the black probe to the stripped contact on the engine or body. Start the engine. The reading on the multimeter should not be more than 15.5 volts whenever the accelerator pedal is pressed. Otherwise, further operation of the generator is dangerous for the electrical equipment of the car.
When checking, you should evaluate the degree of tension of the generator belt. Using a simplified method, this can be done by pressing on the belt with your finger.
The amount of deflection should be within 0.5 - 1 centimeter. At the same time, check the degree of belt wear.
To determine the reasons for abnormal operation of the generator, perform repair work The generator needs to be dismantled.
Checking generator components
The test begins with monitoring the functionality of the voltage regulator. To do this, the regulator is removed from the generator and a simple electrical circuit is created.
Any car interior light bulb can be used as an incandescent lamp. If voltage regulator 3 is working properly, lamp 6 should not glow full power. When connected in parallel with the lamp (brushes) of a multimeter, its readings should be from 5.0 to 10.0 Volts. If the multimeter readings fall outside these limits, the regulator must be changed. The design of some generator models allows for the possibility of replacing the regulator without dismantling the device.
Next, check the exciting winding of the generator for breakdown. To do this, set the multimeter to resistance measurement mode at a limit of 200 kiloOhms. The probes are connected: black - to the commutator lamella, red - to the metal part of the armature. The resistance should be more than 100 kiloohms 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.
Checking the stator begins with checking 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 measurement limit. Then the resistance between the winding contacts is measured. 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 a break, it must be replaced. There are workshops that rewind stators and rotors.
To check the health of the diode bridge, the multimeter measurement mode is switched to the “diode” test. Then the diodes (their number on a horseshoe is usually 9) are sequentially “ringed” in forward and reverse connection. In the forward direction (black probe to the cathode) the resistance is 550 - 700 Ohms, when switched in reverse it is greater than the maximum measurement limit.
When the diodes breakdown, the resistance in all directions will be practically zero. This diode should be changed. The difficulty of replacing a diode lies in the fact that the diodes in generators are not soldered, but spot welded to ensure reliable contact at different temperature conditions.
A car generator is an important part of a car's electrical equipment. At the first sign of inoperability, it is necessary to check it using a multimeter.
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.
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| 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.
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
What to do if there is no light in the house? A current generator can help solve the problem. But if this equipment also fails, checking the generator with a multimeter will help determine the malfunction. Regardless of the type and brand, with the help of this device, once you find out the cause of the malfunction, you can carry out simple repairs yourself.
There are many types of generators, from large and powerful industrial devices to small automotive devices. But the testing algorithm using the tester is the same for any generator.
What components and parts are checked using a multimeter?
This operation involves diagnosing the electrical part, and checking the following parts:
Performing each of the listed operations requires special knowledge and skill to carry out measurements, so each test should be considered in more detail.
Output voltage level measurement
For each individual unit this value will be different. Let's take a closer look at checking a car generator. Set the voltage measurement mode on the multimeter scale. First you need to check the voltage with the engine turned off. To do this, measure the voltage value at the battery terminals.
We connect the red probe to the positive terminal, and attach the black one to the minus terminal. A charged, serviceable battery will produce a value of up to 12.8 V. We start the engine. Then we take a measurement.
Now this value should be no more than 14.8 V, but no less than 13.5 V. If the voltage level is higher or lower, the generator is faulty.
Checking the rotor winding
To perform this operation, it is necessary to dismantle and disassemble the unit. When performing a self-test, do not forget to set the device to the circuit resistance measurement mode.
Additionally, a value of no higher than 200 Ohm is set. These routine maintenance carried out in 2 stages:
- Measuring the resistance value of the rotor windings. To do this, we attach the probes to the rings of the moving part of the engine and determine the value. This will make it possible to determine the probability of a winding circuit break at a value above 5 ohms. If the device shows less than 1.9 ohms, a turn short circuit has occurred. Most often, the chain breaks at the junction of the rotor winding lead to the ring. You can determine the defect by moving the wire with a probe at the soldering points, as well as by detecting darkened and crumbling wire insulation. In the event of a break or short circuit (short circuit), the wires become very hot, so the breakdown can be detected by visual inspection.
- A circuit test is performed to detect a short circuit to the frame. We position the generator rotor conveniently for operation. Then we bring one probe to the rotor shaft, and attach the second to any ring. If the winding is working properly, the resistance reading will go off scale. If it shows low resistance, this part should be sent for rewinding. When rewinding the rotor, it is important to maintain perfect balancing.
Checking the stator windings
Checking the stator begins with a visual inspection. We pay attention to external damage to the housing and insulation, and places where wires are burned during a short circuit.
The faulty unit should be rewound or replaced. If the external integrity of the wires is established, we begin to investigate using a tester.
Before starting work, you should make sure that the unit is disconnected from the network and that there is no contact between the leads of the stator windings.
When performing work to check the normal state of the node, we make sure:
- The integrity of the winding circuit. To do this, set the device to resistance measurement mode. We attach the probes to the first pair of terminals, then check the 1st winding and the 3rd, 3rd and 2nd terminals. If, during a break, the pointer of an analog device goes off the scale, the windings should be rewinded.
- In the absence of an interturn short circuit and to the housing. To do this, connect one of the tips to the terminal, the second to the body. If the windings are short-circuited, the scale will have a lower resistance value than those in good condition.
Voltage Regulator Troubleshooting
Remove and disconnect the wires from the part. We inspect the condition of the brushes. They should not have significant defects or chips. In the guide channels of the brush holder, the generator brushes must move freely. If they protrude beyond the edge by less than 5 mm, the generator regulator should be changed.
The test is carried out using batteries and a 12-volt light bulb. The voltage of the second power source must be at least 15 V, therefore car battery We connect the batteries in series and bring the value to the desired value. We attach the plus from the 1st power source to the output contact, and the minus to ground.
The light bulb is installed between the brushes. When connecting a 16 V source, it should not light up. With a weaker battery, it lights up. If proper combustion is not observed, the regulator should be replaced.
Checking the diode bridge and capacitor
The purpose of this unit is to prevent the passage of electricity to the generator. It must direct it from the generator to the consumer. In this case, any deviation is a malfunction of the diode bridge.
To check, we dismantle it and solder the terminals on the generator. We set the device to “ring”.
To check the power diode, we bring the black probe to the bridge plate, and attach the red probe to the output. If the multimeter reading is 400-800 Ohm, the diode is working, other numbers require replacing the diode or bridge.
When checking the auxiliary diode, the operation is performed in a similar way. But when the probes are swapped, the device should show a resistance value tending to infinity.
To detect a faulty capacitor, you can check it using the “old-fashioned method”. To do this, you need to apply voltage to it for a short time. It should charge.
When its contacts close, a spark should break between them. This means that the capacitor is working.
When checking a polar capacitor, you need to remove the remaining charge. Then, set the resistance measurement on the scale. The contacts must be attached with correct polarity. When measuring a working part, the resistance gradually increases. Otherwise, when the screen shows 0, it should be replaced.
If a non-polar capacitor is being tested, the value scale is set to MOhm. We place the probes on the contacts regardless of polarity. Then, you need to measure the resistance value. If the number on the screen is less than 2 ohms, this is a faulty part.
In conclusion, it is necessary to recall that all measurements when checking the functionality of the generator using a multimeter are carried out by measuring the value of the electric current resistance.
Only to measure the voltage at the output of the generator, the device is configured to measure this value. Any beginner can test a generator with a multimeter. You just need to work with full responsibility and follow the instructions.