How to check the generator for operability? Independent check and repair of the generator

The generator is a kind of power station that provides power to all the engine systems: power, cooling, ignition, so its failure inevitably entails other malfunctions. To prevent damage, it is necessary to systematically carry out its diagnosis, and if problems can not be avoided, immediately repair.

In this article, we'll talk about how to test the generator for performance, without recourse to specialists. But first let's understand the symptoms of its possible malfunctions.

Main signs of generator failure

The fact that the generator has failed, or there are problems in its operation, will prompt the following signs:

• Constant burning of a warning light in the form of a red battery on the dashboard, which indicates that the generator does not give charging, or produces a current of insufficient magnitude;
• Constantly discharging battery;
• Interruptions in the operation of electrical equipment (lighting and alarm, multimedia, heating and ventilation) with the engine running;
• The appearance in the passenger compartment (engine compartment) of a characteristic burnt odor;
• Excessive heating of the stator of the generator;
• Rumble (rustling, whistling) of the generator.

The appearance of such signs is a serious reason for conducting a diagnosis. To do this, it is not necessary to contact the service station, as it is quite possible to check the generator for operation, especially if you have at least the slightest skills of handling the car tester. But first, let's talk about the main breakdowns.

Main Faults

The generator can have malfunctions both mechanical, and electric character. These include:

• Failure of the voltage regulator;
• Faulty diode bridge (rectifier unit);
• Closure of the winding of the excitation of the rotor;
• Closing of stator windings;
• Wear of brushes;
• Wear of bearings.

Next, we'll talk about how to check the generator for performance on its own, based on the symptoms present and possible malfunctions.

Checking the voltage regulator

The regulator is designed to stabilize the voltage produced before being fed to the vehicle's on-board circuit, including the battery for recharging it. Determine its serviceability yourself can only verify the charging of the generator, or rather, the amount of voltage applied to it on the battery terminals. Depending on the make and model of the machine, it can be from 13.5 to 15.5 V. Therefore, before you check the operation of the generator for the correctness of the regulator, you need to know exactly what voltage it should give out. This information can be found in the vehicle's operation manual.

How to check the generator with a multimeter? To do this, switch the device to the voltmeter mode and, observing the polarity, connect its test leads to the battery terminals with the engine not running. Normal voltage is considered to be within 12-12.8 V. Then start the motor and repeat the procedure. The voltage at the battery terminals should rise to 13.5-15.5 V. Only in this case the controller can be considered operable. Increasing or decreasing the magnitude of the voltage, on the contrary, indicates that it is faulty.

How to check the generator diode bridge without removing it from the car

The diode bridge serves as a kind of rectifier, transforming the alternating current generated by the generator into a constant one. Usually it consists of six semiconductor diodes, three of which are "positive", three others are "negative", that is, the first pass current in one direction, the latter in the other direction. The rectifier can be checked both with the generator removed and without dismantling it. Let's consider both variants.

Before checking the diode bridge of the generator without removing it, it is necessary to disconnect from it and from the voltage regulator all the wires, having previously disconnected the "mass" terminal from the battery. First, check the rectifier for a short circuit. We turn on the multimeter in the ohmmeter mode, connect the positive (red) probe to the "30" generator terminal (positive bridge contact), and the negative one to the generator housing. With a working rectifier, the instrument readings will tend to infinity. If the resistance is several ohms, the rectifier is defective.

Now let's talk about how to test the generator's diode bridge for a breakdown. Let's start with positive diodes. Again, connect the positive probe to the corresponding bridge contact (pin "30"), and the negative one to the bolts (brackets) of the rectifier mounting. The resistance must also tend to infinity. Otherwise, one or more diodes are punctured.

We pass to the "negative" semiconductors. The red test lead of the tester is attached to the bolts of the rectifier attachment, the black one to the generator housing. Aspiring to infinity, resistance is a sure sign that the diodes are intact.

Check the rotor winding

A frequent malfunction of the car generator is the closure of the windings. This can happen as a result of a sudden voltage surge, water ingress, wear of brushes, etc. Since it is possible to check the generator with a multimeter for the integrity of its windings, only having received full access to them, it will be necessary to dismantle the entire assembly. We will not describe this process, since it differs from different cars. Before you check the removed generator for the operability of the winding of the rotor, it must naturally be disassembled.

After removing the rotor, we find contact rings on its shaft. There are only two of them. Turning on the multimeter in the ohmmeter mode, connect its probes to these rings. The device should give a resistance within 2-5 ohms. This is normal for a working rotor. A higher resistance indicates poor contact between the rings. In the opposite case, when the instrument readings are approaching zero, the interturn closure is most likely to occur.

How to check the generator for the operation of the stator windings

We pass to the stator. It has several windings, each of which must be checked separately. But before this, it is necessary to disconnect the wires connecting the leads of the windings and the diode bridge.

The probes of the multimeter included in the ohmmeter mode are alternately connected to the terminals of each of the windings. The working winding should have a resistance of about 0.2 ohms.

Then it is necessary to measure the resistance between the common terminal (zero) of the stator and the output of any of the windings. It should be at least 0.3 ohms.

Deterioration of generator brushes

If the generator has been dismantled and dismantled, it will not hurt to check the condition of the brushes. They can fail due to prolonged use, or as a result of problems caused by a distortion of the rotor shaft. If the brushes have traces of great wear, their geometry is broken, they must be replaced.

Wear of generator bearings

The car generator has two bearings. One of them is fixed to the rotor shaft, the second one is pressed in the central part of the cover. The hum, the whistle coming from the generator side while the engine is running, is a sure sign that one of the bearings has been ordered to live for a long time. An attendant symptom may be the heating of the generator housing. Having found out these signs, hurry to replace bearings. Otherwise, this will entail a distortion of the rotor shaft or its jamming with all the ensuing consequences.

Check the bearings by removing the generator belt and turning the shaft with its hand. If the rotor rotates easily, without jerks and backlash, the bearings will still serve. If rotation is difficult, or the shaft has a play, do not pull with bearing replacement.