How to Check Angle Grinder with a Multimeter Video

21st February 2020

Even if a man is not a professional master, but just as a good owner repairs everything in the house himself, he can not do without a quality tool.

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How to Check Angle Grinder with a Multimeter

Visual inspection of breakdown

Any, even the highest quality tool, is prone to breakage. Especially if it is exploited intensively. In the event of a breakdown in the angle grinder, you are unlikely to be able to repair the tool yourself. However, a preliminary examination can be carried out without special skills.

Most often, the Bulgarian anchor fails. Damage can be mechanical. A visual inspection will show uneven wear of the brushes, as well as their burning. In addition, if the anchor is faulty, the angle grinder will vibrate and heat up.

There are electrical breakdowns. These include:

Damage to the armature winding;
The presence of a circuit in the turns;
Broken resistance between the core and the winding.

Such malfunctions can be detected using special measuring instruments, for example, a multimeter.

Check the anchor with a multimeter

In order to conduct such a test, you should disassemble the angle grinder and gain access to the anchor. The multimeter must be put in the range of 200 OM, and with the probes of the device you touch two adjacent slats.

We carry out measurements on all turns of the winding, if all the readings are the same, then the anchor is working. If at some turn the resistance values are different, then there is a malfunction. You should also check the armature winding housing.

Anchor device angle grinder

An engine anchor an angle grinder is a conductive winding and a magnetic circuit into which a rotation shaft is pressed. It has a drive gear at one end, and a lamella collector at the other. The magnetic circuit consists of grooves and soft plates coated with varnish to isolate each other.

Two conductors of the anchor winding are laid in grooves according to a special scheme. Each conductor is a half turn, the ends of which are connected in pairs on lamellas. The beginning of the first turn and the end of the last are in the same groove, so they are closed by one lamella.

How to check the anchor of an angle grinder for serviceability

Types of anchor faults:

Breakdown of insulation to ground is the closure of the winding on the metal housing of the rotor. Occurs due to destruction of insulation.

Wiring of collector conclusions.

Uneven collector wear.

If the anchor is faulty, the motor overheats, the winding insulation melts, the turns are short-circuited. The contacts connecting the armature winding to the collector plates are soldered. The current supply stops and the engine stops working.

Types of diagnostics of the anchor:

Visually;
Multimeter;
A light bulb;
Special devices.

Standard diagnostics

Before taking the device for diagnostics, inspect the anchor. It may be damaged. If the wiring is melted, a burnt insulating varnish will leave black marks or a specific smell. You can see bent and wrinkled turns or conductive particles, for example, solder residues. These particles cause a short circuit between the turns. The lamellas have curved edges, called cocks, for connecting to the winding.

Due to the violation of these contacts, the lamellas burn out.

Other collector damage: raised, worn, or burnt plates. Between the lamellas graphite from the brushes can accumulate, which also indicates a short circuit.

How to check with a multimeter

Set the resistance to 200 ohms. Connect the test leads to two adjacent sipes. If the resistance is the same between all adjacent plates, then the winding is working. If the resistance is less than 1 ohm and very close to zero, there is a short circuit between the turns. If the resistance is above the average two or more times, then there is a break in the turns of the winding. Sometimes, at a break, the resistance is so great that the device goes off scale. On an analog multimeter, the arrow will go all the way to the right. But on digital it won’t show anything.
The determination of the breakdown to mass is done in the absence of a winding break. Put the maximum resistance on the scale of the device. Depending on the tester, it can be from 2 MΩ to 200 MΩ. Connect one probe to the shaft, and the other to each plate in turn. In the absence of faults, the resistance should be zero. Do the same with the rotor. Connect one probe to the iron body of the rotor, and move the other along the slats.

If you do not have a tester, use a light bulb with a voltage of 12 volts with a capacity of up to 40 watts.

How to check the rotor of an angle grinder with a light bulb

Take two wires and connect them to the lamp.
Make a break on the negative wire.
Apply voltage to the wires. Attach the ends of the gap to the plates of the collector and scroll it. If the light is on without changing the brightness, then there is no short circuit.
Carry out an iron short circuit test. Connect one wire to the slats and the other to the rotor iron. Then with the shaft. If the light is on, then there is a breakdown to ground. The winding closes to the rotor housing or shaft.

This procedure is similar to multimeter diagnostics.

Check by indicator of short-circuited turns (ICZ)

There are anchors that do not show wires connected to the collector due to the filling with an opaque compound or because of the bandage. Therefore, it is difficult to determine commutator switching relative to the grooves. The indicator of short-circuited turns will help in this.

This appliance is small and easy to operate.

First check the anchor for breaks. Otherwise, the indicator will not be able to detect a short circuit. To do this, measure the resistance between two adjacent lamellas with a tester. If the resistance exceeds the average at least twice, then there is a break. If there is no break, proceed to the next step.

The resistance regulator allows you to select the sensitivity of the device. He has two bulbs: red and green. Adjust the control so that the red light starts to light. On the indicator housing there are two sensors in the form of white dots located at a distance of 3 centimeters from each other. Attach the indicator with sensors to the winding. Slowly twist the anchor. If the red light comes on, there is a short circuit.

Diagnostics by the instrument for checking anchors (throttle)

An anchor test device determines the inter-turn winding circuit. The inductor is a transformer that has only a primary winding and cuts the magnetic gap in the core.

When we put the rotor in this gap, its winding starts to work like a secondary winding of a transformer. Turn on the appliance and anchor a metal plate, such as a metal ruler or hacksaw blade. If there is an interturn closure, the plate will vibrate or magnetize to the armature body from local glut of iron. Turn the anchor around the axis, moving the plate so that it lies on different turns. If there is no short circuit, then the plate will move freely along the rotor.

How to repair an anchor at home

Because of the anchor, a third of screwdriver breakdowns occur. With daily intensive operation, malfunctions can occur already in the first six months, for example, with untimely replacement of brushes. With gentle use, a screwdriver will last a year or more.

An anchor can be saved if the balance is not disturbed.

Collector groove

Over time, brush generation develops on the collector. To get rid of it, you must:

Grind the collector using cutters for longitudinal turning, i.E. Through cutters.
We also need a reverse cone to center the bearing. Make a hole in it up to 8 mm.
Since copper is viscous, adjust the machine for the number of revolutions from 600 to 1500 per minute.
Primary feed in half division. When the cutter slightly touches the product, groove the entire collector. According to the resulting brilliant pattern, you will see the state of the lamellas, all the surface irregularities.
If the collector is even, the groove will be uniform.
If there are holes, then continue grooving until the surface is flat.
For the last pass, you need to file a cutter one fourth from the division.
For polishing, take sandpaper with a thousandth grit and turn on the machine so that the anchor rotates in the direction it rotates during operation.

Do not forget to clean the rotor of chips so that there is no short circuit.

How to rewind an anchor

Before disassembling the anchor, write down or sketch the direction of the winding. It can be left or right. To determine it correctly, look at the end of the anchor from the side of the collector. Put on gloves, take sharp nippers or a hacksaw for metal. Remove the frontal parts of the winding. The collector needs to be cleaned, and it is not necessary to remove. Carefully, without damaging the slot insulators, knock out the rods of the remaining parts of the winding with a hammer and a metal chisel.

Video: Remove the winding

File, without damaging the insulator film, remove the remaining impregnation. Count the conductors in the groove. Calculate the number of turns in the section and measure the diameter of the wire. Draw a diagram. Cut the insulation sleeves from the cardboard and insert them into the grooves.

Video: Winding left and right

After winding, weld the conclusions of the sections with the headers of the collector. Now check the winding with the tester and short circuit indicator. Proceed to soak.

Impregnation instructions (taking into account the speed controller)

After making sure that there are no problems, send the anchor to the electric oven for heating for better flow of epoxy.
After warming up, place the anchor on the table at an angle for better spreading over the wires. Put a resin on the frontal part and slowly twist the anchor. Drip until glue appears on the opposite frontal part.
Position the anchor horizontally and drip onto both frontal parts. Twist the anchor to yield strength.
Leave in an upright position until fully polymerized.

At the end of the process, slightly pierce the collector. Balance the anchor with dynamic balancing and angle grinder. Now grind completely on the bearing. It is necessary to clean the grooves between the lamellas and polish the collector. Make a final check for open and short circuits.

The peculiarity of the winding for grinders with an adjustable speed is that the rotor is wound with a power reserve. The current density affects the speed. The wire cross section is overestimated, and the number of turns is underestimated.

Repair: Elimination of breakdown of insulation

If the breakdown of the insulation was small and you found it, you need to clean this place from soot and check the resistance. If its value is normal, insulate the wires with asbestos. From above drip with quick-drying glue like “Super moment”. It seeps through asbestos and insulates the wire well.

If you still have not found a breakdown location of insulation, then carefully impregnate the winding with an impregnating insulating varnish. Punched and unbroken insulation will be impregnated with this varnish and will become stronger. Dry the anchor in a gas oven at a temperature of about 150 degrees. If this does not help, try rewinding the winding or changing the anchor.

Soldering manifold plates

The slats are mounted on a plastic base. They can be erased to the very core. Only the edges remain to which the brushes do not reach.

Such a collector can be restored by soldering.

From the copper pipe or plate, cut the required number of lamellas by size.
After the anchor has been cleaned of the remains of copper, solder with ordinary tin with soldering acid.
When all the lamellas are soldered, grind and polish. If there is no lathe, use a drill or screwdriver. Insert the armature shaft into the chuck. Sand with a file first. Then polish with zero sandpaper. Remember to clean the grooves between the lamellas and measure the resistance.
There are not completely damaged lamellas. To restore them, more thorough preparation is necessary. Lightly tap the manifold to clean the plates.
The place under the plate must be expanded with a drill carefully so as not to remove a large layer of insulator.
Find two pieces of copper wire of such a size that they fit snugly into the groove formed. Place the cleaned wires in the groove and tin.
Make a copper lamella blank. It should fit snugly and be taller than existing lamellas to make soldering easier.
Surround the workpiece so that there is a lot of solder. She will sit denser in the groove. Place the workpiece in the groove and attach a soldering iron to it. Hold it until the solder melts.
Drain the excess with a file, sand and polish.

If the collector was completely worn out, then after soldering it will be enough for no more than a month of active use. And not completely damaged plates after such a repair can withstand several brush changes and do not evaporate.

Galvanic expansion of collector plates

Reconditioned copper is very hard. The life of the collector is like new. By galvanic build-up, it is possible to restore both a completely wiped collector and partially damaged plates.

The quality of recovery will be the same.

Clean the entire collector surface well, including the insulator between the lamellas.
Wind a bare copper wire with a diameter of about 0.2 millimeters.
Tape the anchor shaft with tape, and coat the collector from the end with plasticine so that the copper does not grow where it is not necessary. And so that the electrolyte does not get on the iron.
For the bath, cut the floor of the plastic bottle. Wrap electrical tape around the shaft so that it snugly holds in the neck of the bottle. Insert the anchor into the bottle.
Take a piece of copper bar. Its size is two times the stackable surface. Roll it into a spiral and place it in a bottle.
Connect the power supply minus to the surface being restored, and plus to the busbar. One and a half amperes of current per one square decimeter of solution. If the collector is separated from the shaft, wrap it with wire and hang it in a jar on some crossbar so that the electrolyte touches only the worn part of the lamellas. Connect light bulbs of different capacities in series to regulate the amperage and to prevent a short circuit on the vessel. After 24 hours, a restored collector is obtained.
The collector must be grooved and the plates divided with a drill or hacksaw blade. Finally, test the manifold for shorts between the plates.

Components of electrolyte:

Copper sulfate. 200 g.
Sulfuric acid 1.84. 40 g.
Alcohol. 5 g. It can be replaced with a triple amount of vodka.
Boiled water. 800 ml.

How to exchange an old gearbox for a new one

Angle grinder differ in size, power, manufacturers, but the principle of component arrangement is the same. The new motor anchor angle grinder is selected strictly in accordance with the model of your tool.

After unscrewing all the mounting bolts of the casing, housing and gearbox, we remove the gearbox with an anchor from the housing. Typically, the gearbox and the armature are firmly attached to each other. To separate them, it is necessary to disassemble the gearbox.
Turn off bolts of fastening.
The rotor shaft is screwed to the gear housing with a nut. Unscrew it. Remove the gear.
Next comes the bearing. To remove it, sometimes it is enough to knock a wooden block on the gear case. But more often than not the sticky bearing cannot be removed without some tricks. Between the impeller and the bearing there is a plate, which is bolted with two bolts to the gearbox. To reach them, break off a piece of plastic impeller or burn two symmetrical holes with a heated nail. The second hole is necessary for balancing if you are not going to change the impeller.
Unscrew both bolts, tap the gear case with a wooden block, and the anchor will detach from it. In this case, the bearing will remain on the shaft. Remove all bearings from the shaft with a puller.

Place the new bearing in the gear housing on the rotor side. Screw on the plate due to which the impeller was broken. Insert the gear inside the housing and loosen the nut so that it fits into the grooves of the gear. Put the impeller on the new anchor, insert the anchor into the gear housing. Tighten the nut.

Features of the asynchronous motor angle grinder

In almost all electrical appliances used in everyday life, an asynchronous electric motor is used. An important advantage of this type of motor is that when the load on it changes, the speed does not change. This means that if, for example, you cut a stone for a long time and without stopping a household angle grinder, there will be no noticeable external signs of engine overload. The speed of rotation of the disk will be constant, the sound is monophonic. Only the temperature will change, but this may not be noticed if the hands are wearing gloves.

With an inattentive attitude, an advantage can turn into a disadvantage. Asynchronous motors are very sensitive to overheating, a significant excess of the operating temperature entails a melting of insulation on the rotor windings. At first, the motor will work intermittently, and then. When an inter-turn short circuit occurs. The engine will stop completely. It is necessary to overheat the engine several times with an angle grinder and, most likely, the anchor will melt. In addition, contacts connecting the wires of the primary winding to the collector are soldered from high temperature, which leads to an interruption in the supply of electric current.

How to determine the malfunction of an anchor angle grinder

Signs of an anchor breakdown in an angle grinder are: increased sparking of brushes on the motor manifold, vibration of the motor at low speeds, rotation of the working shaft in different directions. If such symptoms are present, work with the tool should be stopped. This is dangerous. Suspicions are easy to verify with simple tests.

Visual inspection from the outside

Troubleshooting should begin with a visual inspection of the angle grinder:

Carry out a general inspection of the tool.
Pay attention to the integrity of the power cord, the presence of voltage in the outlet.
Using a voltage indicator, make sure that current flows to the engine manifold and start button.

Inspection of the device from the inside

If everything is in order with power, but the angle grinder does not work, you will have to open the case to gain access to the motor. As a rule, disassembly is not difficult. But you need to adhere to simple rules that will avoid troubles during the reverse assembly:

Be sure to unplug the appliance before disassembling.
Remove the working disk and the protective cover from the spindle.
Open the case in a well-lit place, on a clean table surface.
Remember the location of all parts and assemblies before disassembling. It is recommended to sketch or photograph the internal structure of the device.
Fold the screws and fastening screws in a separate place so as not to get lost.

Inspecting the motor is best done under bright light, so that all the small details are clearly visible. The anchor should rotate freely around its axis, properly working bearings should not make a sound during operation. There should be no traces of melted wiring at the anchor, the circuit windings must be intact, without breaks. You can smell the rotor. During interturn closure, the insulating varnish burns and emits a stable specific odor. But for such a diagnosis, some experience is needed.

Circuit Tester

If a visual examination does not give obvious results, it is recommended to continue the examination with a multimeter. Having set the mode switching toggle switch to the ohmmeter position (range 200 Ohms), it is necessary to “ring” two adjacent anchor lamellas with two probes. If the resistance on all turns is the same, it means that the windings are working. If on some pairs the tester shows a different resistance or an open circuit, there is a malfunction in this coil.

Rupture of the wiring may occur between the winding and the core. It is necessary to carefully examine the junction of the coils with the collector lamellas in the lower part of the armature, visually check the soldering of contacts.

Checking contacts with a light bulb

If there is no tester, you can get out of the situation with a simple 12 volt bulb. Power can be any, optimally 30–40 watts. The voltage from the battery 12 volts must be fed to the plug angle grinder, inserting a light bulb into the gap of one wire. With a working anchor, if you rotate the spindle by hand, the bulb should light up without changing the brightness. If the glow changes, this is a sure sign of an inter-turn short circuit.

If the light does not light, then this may indicate the following:

Hanging of brushes in a non-working position is possible. The retaining spring worked.
There was a break in the supply circuit.
A short circuit or rupture has occurred in the stator winding.

There are other diagnostic methods, but they require more sophisticated equipment, which is usually not used at home. An experienced master will determine the failure with a high degree of accuracy using a “punch” or a simple transformer with a cut toroidal core and one primary winding.

In what cases can you save the anchor and restore it with your own hands

If damage to the armature is established with guaranteed accuracy, the part must be removed from the electric motor. The motor must be disassembled with special care, after removing the brushes and disconnecting the power terminals. The rotor is removed along with the thrust bearings and the cooling wheel of the motor, they form a whole with it.

If most of the wiring is damaged in the anchor and the balance is disturbed as a result of overheating, it is better to replace it entirely. An imbalance is indicated by increased vibration and an uneven hum during the operation of the mechanism.

How to rewind an anchor. Step by step instructions

If the balancing of the armature is not broken, and the problem is only in damaged windings, then such an armature can be restored independently by rewinding the coils. Rewinding a rotor at home requires a lot of patience and accuracy.

The master must have skills in working with a soldering iron and devices for diagnosing electrical circuits. If you are unsure of your abilities, it is better to take the engine for repair to the workshop or replace the entire anchor yourself.

For independent rewinding of the anchor you will need:

Wire for a new winding. A copper core with a diameter exactly matching the old conductor is used;
Dielectric paper to isolate the winding from the core;
Varnish for pouring coils;
Soldering iron with tin-lead solder and rosin.

Before rewinding, it is important to count the number of turns of wire in the winding and wind the same amount of new conductor onto the coils.

The rewinding process consists of the following steps:

Dismantling of old windings. They must be carefully removed without damaging the metal body of the anchor. If any burrs or damage are found on the case, they must be ironed or sanded. Sometimes, to completely clean the body of toxins, masters prefer to burn it with a burner.
Preparing the collector for connecting a new wire. There is no need to remove the collector. It is necessary to inspect the lamellas and measure the contact resistance with a megger or multimeter with respect to the housing. It should be no more than 0.25 megohms.
Removing old wiring to the collector. Carefully remove the remnants of the wires, cut the grooves in the part of the contacts. Subsequently, the ends of the wires of the coils will be inserted into the grooves.
Installation of sleeves for an anchor. The sleeves are made of dielectric material with a thickness of 0.3 mm, for example, electrical cardboard. Cut a certain number of sleeves and insert into the grooves of the peeled anchor.
Rewind reels. The end of the new conductor is attached to the end of the lamella and wound in successive circular motions, counterclockwise. This installation is called “right installation”. Winding Repeat for all coils. Pull the wires near the collector with a thick thread of cotton fabric (nylon is prohibited, since it melts when heated).
Checking the quality of the winding. At the end of laying all the windings, check with a multimeter for the absence of inter-turn short circuits and possible breaks.
Finishing Finish the finished coil with varnish or epoxy to fasten the winding. In the factory, the impregnation is dried in special ovens. At home, this can be done in the oven. As an option. Apply quick-drying varnishes for impregnation, applying a coating in several layers.

Replacing the anchor yourself at home

Practice shows that if it is decided to replace the anchor with an angle grinder, then it is best to change it together with the thrust bearings and the cooling wheel of the engine.

To replace you will need:

New anchor angle grinder. Must fit your model. Interchange with other models is not allowed.
Screwdrivers, wrenches.
Soft brush and rags for cleaning the mechanism.

How to remove the anchor

Replacing the anchor begins with the disassembly of the angle grinder. The following steps are taken:

The brush nodes are twisted with a screwdriver on both sides. Brushes are removed.
4 screws securing the gear housing are removed.
The gearbox cover is carefully opened and removed to gain access to the inside of the gear mechanism.
The snap ring is removed, fixing the small gear on the anchor.
The anchor retainer is released from attachment, the anchor is removed along with the small gear and bearing.
The gear, the bearing and the fixing disk of the anchor are removed, wiped with a rag. The bearing is removed with a special puller.

Video: replacing bearings with an angle grinder

How to anchor in place

To reinstall the new anchor, the angle grinder should take a new part, and then assemble the tool in the reverse order. The sequence of actions is as follows:

A fixation disk is mounted on the armature shaft.
The bearing is mounted by pressing.
The small gear is put on and fixed by a lock ring.
The anchor is inserted into the gear housing, the docking holes are combined.
The gearbox mounting bolts are tightened.
An anchor with a reducer is inserted into the body of an angle grinder and fixed.
Brushes are deposited in place, closed with lids.

After performing these steps, the angle grinder is ready for use. Replacement of the anchor made.

Video: how to check the angle grinder

Ancient Sufi wisdom says: “The person who is able to get out of a difficult situation with dignity is smart. But wise is he who does not fall into such a situation. ” Observing the rules for operating household appliances, preventing the motor from overheating, you can avoid breakdowns and troubles in the work of an angle grinder. Keeping the instrument clean and dry will prevent its mechanisms from contaminating and oxidizing current-carrying elements. Timely maintenance of the tool is guaranteed to relieve unpleasant surprises during operation.

Dismantling angle grinder

To check the short circuit on the stator and rotor, you need to disassemble the engine of a household tool. Consider performing this operation to troubleshoot an angle grinder.

Remove the protective cover by unscrewing one screw on the clamp;
Unscrew the 4 screws and disconnect the gear with the engine from the handle of the angle grinder;
Then on the gearbox side, unscrew 4 bolts and disconnect the gearbox, together with the motor rotor;
The stator in our case remained connected to the power and power button.

Having disassembled and disconnected the parts necessary for verification, we proceed to their external inspection by checking for inter-turn closure.

Visual inspection

A malfunction can be detected by uneven heating of the tool body. Touching your hand, you feel the temperature difference in different places of the case. In this case, the tool must be disassembled and tested with a tester and other methods.

In the event of a short circuit of the stator turns and troubleshooting, first of all, we conduct an inspection of the turns and conclusions. As a rule, when closing, the current flowing through the windings increases, and their overheating occurs.

There is a greater closure of the turns in the stator windings and the insulation layer is damaged. Therefore, we begin the determination of malfunctions by conducting a visual inspection. If burn-through and damaged insulation are not found, then proceed to the next step.

Perhaps the cause of the breakdown is a malfunction of the voltage regulator that occurs when the excitation currents increase. To detect a problem, the brushes are checked, they must be sharpened evenly and not have chips and damage. Then check with a light bulb and 2 batteries.

Multimeter application

Now we need to check the possibility of breaking the stator windings. On the multimeter scale, set the switch to the resistance measurement sector. Not knowing the measurement value, set the maximum value for your device. We check the performance of the tester.

Touch probes of each other. The arrow of the device should show 0. We carry out the work, touching the conclusions of the windings. When an infinite value is shown on the multimeter scale, the winding is faulty and the stator should be rewound.

We check the possibility of a short circuit to the case. Such a malfunction will cause a decrease in power of the angle grinder, the possibility of electric shock and an increase in temperature during operation. The work is carried out according to the same scheme. We include resistance measurement on the scale.

We place the red probe on the output of the winding, and attach the black probe to the stator housing. If the winding is shorted to the housing on the tester scale, the resistance value will be less than on a healthy one. This malfunction requires rewinding of the stator windings.

It is time to take measurements and check if there is an interturn circuit of the stator winding. For this, the resistance value on each winding is measured. We determine the zero point of the windings by measuring the resistance for each of them. If the device shows the least resistance of the winding, it should be changed.

Custom check

The most accurate way is to check the stator using a metal ball and a step-down current transformer. The stator is connected to the terminals of the three phases from the transformer. After checking the correct connection, we turn on our low-voltage circuit in the network.

We throw a ball inside the stator and observe its behavior. If it “stuck” to one of the windings. This means that an interturn circuit occurred on it. The ball spins in a circle. The stator is working. A rather unscientific, but effective method for detecting interturn circuit on a stator.

Rotor malfunctions

In the case of optimal use, the rotor does not wear out. Routine maintenance is carried out with the replacement of the brushes when they are worn. But over time, under heavy loads, the stator heats up and carbon deposits form. The most common mechanical failure is wear or misalignment of the bearings.

The angle grinder will work, but at the same time, the plates quickly wear out, and over time the engine breaks. To avoid damage, it is necessary to check the tool and maintain normal conditions of service. Moisture in contact with metal causes the formation of rust. The frictional force increases, the current strength is required more to work. Significant heating of contact groups occurs, solder, a strong spark appears.

Checking motor windings

The electronic rotor tester is a standard digital multimeter. Before proceeding to test the circuit, you should check the multimeter and its readiness for work. The switch is set to measure the resistance and touch the probes with each other. The device should show zeros. Set the maximum value of the measurement and check:

First check the rotor for an open circuit. Touching the black probe to the slip ring, the windings should ring red. The arrow of the device is off scale, which means that the winding has an open circuit of turns. The rotor should be rewound;
Measure the resistance to determine the possibility of a short circuit to the housing. We fix the black probe on the contact ring, the red rotor should ring to close the rotor case. In the case of a low reading of the resistance value and the sound signal, such an anchor must be given for repair;
Conducting ringing on the inter-turn circuit of the turns of the rotor. We reinforce the probes on the contact rings of the anchor. With a value on the scale of the device, from 1.5 Ohms to 6 Ohms, we tested a working device. All other values on the scale indicate a malfunction of the multimeter.

This completes the verification of the rotor. Once again, the main steps in determining the malfunction should be recalled. Before checking, the angle grinder or any other device should be de-energized. Before taking measurements, you should visually inspect the housing, insulation and lack of deposits on the stator and rotor.

It is necessary to clean the contact surfaces from blockages with dust and dirt. Pollution leads to an increase in current during loss of motor power.

When disassembling the tool for the first time, record all your steps. This will allow you to have a hint the next time, to avoid the appearance of unnecessary parts during assembly. When the brush leaves the edge of the brush holder less than 5 mm, such brushes should be replaced. You can check the inter-turn circuit with an electronic tester, that is, a multimeter.

Source

Angle Grinder angle, check, grinder, multimeter, video