Sudden stoppage of the refrigerator or its failure to maintain the set temperature often indicates problems with the compressor. This is the heart of the unit, and if it stops beating, food spoilage begins. One of the most common causes of failure is damage to the electrical part of the engine, in particular stator windings. It is they who create the magnetic field necessary for rotor rotation.
Before calling a technician or buying a new refrigerator, it is worth conducting an initial diagnosis. In many cases interturn closure or a wire break can be detected independently using a regular multimeter. This will save time and help you understand whether repairs are worth the investment or whether it’s easier to replace the entire unit. We will analyze all stages of testing from preparing tools to deciphering instrument readings.
It is important to understand that working with electricity requires strict adherence to safety precautions. Even if the refrigerator is unplugged, residual charges may remain inside the compressor, and careless handling of the wires may lead to a short circuit the next time it is started. Therefore, all manipulations are carried out only with the device completely de-energized and disconnected from the outlet.
Principle of operation and types of electric motor windings
The compressor of a domestic refrigerator is a sealed unit, inside which the electric motor is located. To start and operate this engine, two main windings are used: starting and working. They are wound with copper wire on the stator core and have different electrical characteristics. The working winding is designed to maintain rotor rotation; it has a thicker wire and less resistance.
The starting winding is switched on only at the moment of start, creating the necessary shearing torque. It is made of thinner wire, which causes its high electrical resistance. After the rotor accelerates, the starting winding is turned off using a starting relay or capacitor (depending on the engine model). If you mix up these windings when connecting, the engine will hum, but will not start, which will quickly lead to its overheating.
Some modern models use motors with third winding or inverter circuits, where the control occurs differently, but the classic circuit with two windings remains the standard for most household refrigerators, such as Atlant, Biryusa or old models Indesit. Understanding the differences between them is critical for correct diagnosis.
- 🔌 The working winding has low resistance and a thick wire, responsible for the main operating mode.
- 🚀 The starting winding has a high resistance and serves only to start the engine.
- ⚡ The third winding (less common) can be used for additional modes or working with an inverter.
⚠️ Attention! Never try to start the compressor by applying voltage directly to the starting winding as a work winding. This is guaranteed to lead to the engine burning out in a matter of seconds due to overheating of the thin wire.
Necessary tools and safety measures
To carry out high-quality diagnostics, you will need a minimum set of tools, which most home craftsmen can find. The main device is multimeter (tester), capable of measuring resistance in the range from 0 to 20 kOhm. It is advisable that the device is in good working order and has charged batteries, since the accuracy of the readings depends on this.
You will also need screwdrivers to remove the protective casing of the compressor and the terminal box. In some cases, sandpaper may be necessary to clean the contacts if they have oxidized. Before starting work, make sure that the refrigerator is unplugged from the power supply for at least 15-20 minutes to allow the capacitors to discharge.
Pay special attention to visual inspection. If you see melted plastic, traces of burning, or hear the smell of burnt insulation, further diagnostics with a multimeter may be unnecessary - the engine requires replacement. However, to accurately confirm the diagnosis, instrumental monitoring is required.
☑️ Preparation for diagnosis
Procedure for accessing the compressor contacts
To get to the winding terminals, you need to remove the protective casing at the back of the refrigerator. It is usually secured with latches or screws. Inside you will see a black compressor barrel, which is connected to a start relay and a protective thermal relay. It is on the contacts of the relay or the compressor itself (if you remove the relay) that measurements will be taken.
Carefully remove the start relay. It can be held on by latches or simply put on the contacts. Below the relay you will see three terminals forming a triangle. On some models they are marked with letters: S (Start - launch), R (Run - working) and C (Common - general). If there are no markings, the location of the contacts must be determined experimentally or according to the diagram in the technical documentation.
Before connecting the multimeter probes, make sure that the contacts are clean and free of oxides. If necessary, clean them with an eraser or fine sandpaper. Oxidation can introduce an additional error in measurements, although when checking for a break this plays a lesser role than when checking resistance.
How to remove a relay without damage
The relay can dry out over time. Do not jerk it sharply by the wires. Gently rock from side to side, using a flathead screwdriver to help if there are latches. The main thing is not to break the plastic housing of the relay, since finding a replacement for a specific model can be difficult.
Method of checking with a multimeter for opens and shorts
Switch the multimeter to resistance measurement mode (Ohm, indicated by the symbol Ω). Select a measurement limit of 2000 ohms (2 kohms) or 20 kohms. First check the device by shorting the probes with each other - it should show zero or close to zero. Now let's start diagnosing the compressor terminals.
Find the common terminal. To do this, call your contacts in pairs. Between the two terminals the resistance will be greatest (the sum of the resistances of the starting and operating windings). The third pin, which is not involved in this pair with maximum resistance, will be common contact. From it to the working terminal the resistance will be average, and to the starting terminal - the largest of the remaining ones.
Normal resistance values for a working motor vary depending on the power and model:
- 📏 The resistance of the working winding is usually from 10 to 30 Ohm.
- 📏 The resistance of the starting winding is usually in the range from 30 to 100 Ohms.
- 📏 The total resistance between the extreme contacts (without common) is equal to the sum of the two previous values.
If the multimeter shows one (infinity) on any of plots, this means winding break. The engine is burnt out and cannot be restored at home. If the device shows zero, it means that a short circuit has occurred in the turns, which also requires replacing the compressor.
⚠️ Attention! The resistance numbers may “float” in the first seconds of measurement. Allow the readings to stabilize. Also remember that a cold motor has less resistance than a warm one.
Diagnostics of interturn short circuit and breakdown to the housing
The most insidious malfunction is turn-to-turn short circuit. In this case, the winding is intact, there is no break, and the resistance may be even close to normal, but the motor hums, overheats and knocks out the thermal relay. An accurate diagnosis in this case is made by current consumption, but can be indirectly judged by the underestimated resistance of the working winding relative to the passport data.
The second critical parameter is breakdown on the housing. This is a situation where a phase shorts to a metal part of the compressor or a copper tube. This is deadly for humans and leads to constant tripping of the RCD or knocking out traffic jams. To check, switch the multimeter to continuity mode (with sound) or resistance measurement to the maximum limit (MOhm).
Press one probe to the cleaned place on the compressor housing (where there is no paint), and touch the second to each of the three contacts. The device should be silent and show infinity. Any squeak or appearance of numbers on the screen indicates an insulation breakdown. It is prohibited to operate such a refrigerator.
| Type of malfunction | Multimeter readings | Symptoms during operation | Solution |
|---|---|---|---|
| Break winding | Unit (∞) on one of the contacts | Silent, does not start | Replacement of the compressor |
| Short circuit | Zero (0) or very few Ohms | Knocks out the machines, smoke | Replacing the compressor |
| Breakdown to the housing | Resistance between the contact and the housing | Electric shock, tripped RCD | Urgent replacement, dangerous! |
| Interturn short circuit | Resistance is 20-30% below normal | Buzzes, gets hot, relay clicks | Replacement compressor |
Frequent diagnostic errors and their consequences
Beginners often make mistakes that lead to false conclusions. One of them is measuring resistance with dirty hands or touching the metal parts of the probes with your fingers. The human body has its own resistance, which can distort the readings of the device, especially at high measurement limits. Hold the probes only by the insulated handles.
Another mistake is ignoring the state of the contacts. If the terminals are oxidized, the multimeter will show a break where there is none. Always clean contacts before testing. Also, do not forget about thermal relay, which is in the chain. If you call the circuit through the relay, and it is faulty (open), you may mistakenly diagnose a broken motor winding.
Remember that a hermetic compressor is a complex assembly. If you are not confident in your abilities or the readings from the device are contradictory, it is better to turn to professionals. Inept intervention can lead to depressurization of the system and leakage of freon, which will require expensive refilling.
What to do if the resistance is normal, but the refrigerator does not work?
If the windings are intact and there is no breakdown, the problem may be in the starting relay, which does not supply an impulse to the starting winding, or in the thermostat, which does not gives the command to turn on. It is also possible that the mechanical part of the compressor (piston group) becomes jammed when the electrics are working properly, but the motor is physically unable to turn.
Is it possible to rewind the refrigerator compressor yourself?
Theoretically it is possible, but in practice it is impractical. To rewind, you need a special machine, a wire of a certain cross-section and grade, as well as the ability to correctly lay the windings. The cost of work and materials often exceeds the price of a new compressor, and the reliability of such rewinding will be low.
Why does the compressor hum, but does not start?
The hum means that current is supplied to the working winding, and a magnetic field is created, but the rotor does not budge. Most often, the starting relay is to blame (the tablet or contacts have burned out) or the mechanics have jammed. Less often, the starting winding has burned out, and the engine does not receive a starting impulse.