Faced with a refrigerator that refuses to start or a characteristic hum without further work, many equipment owners immediately blame the compressor. Indeed, this unit is the heart of the cooling system, and it is on its serviceability that it depends on whether there will be cold in the chamber. However, before writing off the unit and looking for a replacement, it is necessary to conduct an initial diagnosis of the electrical part of the motor. Often the problem lies not in mechanical jamming, but in a break or inter-turn short circuit inside the stator.
Understanding where is which winding located and how they interact is a key skill for any home handyman. Compressors of household refrigerators, whether models Atlant, Indesit or Beko, are most often equipped with asynchronous electric motors with a starting winding. Knowledge of the connection diagram and the ability to use a multimeter will allow you to accurately determine the condition of the engine without expensive service.
In this article we will analyze in detail the device of the motor-compressor, consider methods of visual and instrumental control, and also provide a table of normal resistance values for various types of units. You will learn to distinguish the starting winding from the working winding and understand why resistance plays a decisive role in starting the engine.
The design of the motor-compressor and the role of the windings
The electrical part of a standard hermetic compressor is an asynchronous motor with a squirrel cage rotor. Inside the stator there are two main windings: working (main) and starting (auxiliary). The working winding occupies most of the stator slots and is designed to create the main magnetic flux during engine operation. It is this that consumes the bulk of the electricity in normal mode.
The starting winding has a smaller number of turns, but they are made of wire of a smaller cross-section, which creates a difference in electrical characteristics. Its task is to create a current phase shift necessary for the generation of torque at the moment the rotor starts. Without this winding, the engine would only hum, trying to move, but rotation would not occur. After starting, the starting winding must be turned off, otherwise it will burn out due to overheating.
The auxiliary circuit is switched off automatically using the starting relay. Older models use start-up protection relays with a posistor or an electromagnetic mechanism, while more modern ones use electronic control units. It is critically important to understand that the starting winding only works for a split second at start, while the working winding functions constantly. Violation of this balance, for example, sticking of the relay contacts, leads to rapid failure of the compressor.
The three leads coming out of the compressor housing exactly correspond to the ends of these windings and their common point. The location of the contacts on the terminal block may vary depending on the manufacturer, be it Danfoss, Secop or Chinese analogues Jiaxipera. Therefore, you cannot rely only on the location of the pins - it is necessary to take measurements.
Why do the windings burn out?
Most often, the reason for the failure of the windings is not the quality of the wire, but a violation of operating conditions. Working in the non-switching mode (too frequent start-stops), low voltage in the network or a malfunction of the thermostat leads to overheating and destruction of the varnish insulation of the wires.
Necessary tools and safety measures
Before starting diagnostics, it is necessary to prepare the workplace and tools. The main device for testing is multimeter (tester). You will need a resistance measurement mode (Ohm) and, preferably, a dialing mode with a sound signal. For deeper diagnostics, professionals also use a megohmmeter to check the insulation resistance, but at home a high-quality digital multimeter is sufficient.
In addition to the measuring device, you will need:
- 🔧 A set of screwdrivers for dismantling the protective casing and removing the terminal block pads.
- ✂️ Side cutters or a knife for stripping contacts (if the terminals are oxidized).
- 🧤 Dielectric gloves for protection against accidental electric shock.
- 📸 Smartphone for photographing the connection diagram before disassembling.
Safety is priority number one. All work must be carried out exclusively under power off. Unplug the refrigerator from the socket. Even after switching off, the capacitors in the start relay may retain a charge, so do not touch live parts with your bare hands immediately. Also make sure that the compressor has cooled down if it tried to work before.
⚠️ Attention: It is strictly forbidden to measure resistance or continuity of the windings while the compressor is connected to the mains. This will lead to instant failure of the multimeter and can cause serious electrical injury.
If you find traces of oil, soot or a burning smell on the compressor housing, this may indicate an insulation breakdown and a short circuit of the windings to the housing. In this case, diagnostics with a multimeter may show the absence of resistance between the contacts, but the presence of a leak to ground.
Visual inspection and access to contacts
Diagnostics begins with a visual inspection. Remove the back cover of the refrigerator to gain access to the motor-compressor. Pay attention to the condition of the surface of the unit. If you see obvious signs of overheating, melted paint, or, worse, a hole in the housing with leaked oil, further electrical checks make no sense - the compressor requires replacement. However, if there are no visual defects, we move on to the contact group.
At the end of the compressor there is a terminal block covered with a plastic box. Carefully remove the fasteners or unscrew the screw holding the cover in place. Under it you will see three contacts coming from the compressor and corresponding connectors from the start relay. Contacts may be marked, but this is not always standard. Often there are designations C (Common - general), R (Run - working), S (Start - starting).
In some models, for example, in compressors Atlant or Biryusa, markings may be absent altogether, or located non-standardly. Therefore, you can rely on letters only as an auxiliary guide. The main rule of contact geometry: if you look at the block from above, then the common contact is often (but not always!) located separately, and the other two are located next to each other. Or they form a triangle. The exact location depends on the manufacturer: y Danfoss it is one, y Lg is another.
Before taking measurements, be sure to remove the starting relay and the protective casing from the compressor contacts. You need direct access to the three pins coming out of the sealed housing. Clean them as necessary to ensure reliable contact between the multimeter probes. Oxides can introduce a significant error in measurements.
Method of testing and determining windings
The most reliable way to determine which winding is which is by measuring the resistance between pairs of contacts. Set the multimeter to resistance measurement mode at the 2 kOhm limit (or 2000 Ohm). Apply the probes alternately to pairs of contacts. We have three contacts in total, which means there are three possible pairs: 1-2, 2-3 and 1-3.
Write down the readings for each pair. The logic of the definition is based on a physical law: starting winding it is wound with a thinner wire and has a larger number of turns (in relative terms to create a phase shift in some designs) or, which is more typical for refrigeration compressors, it has higher resistance compared to the working one. The working winding is made of thicker wire and has lower resistance.
Action algorithm:
- Measure the resistance between all three pairs of contacts.
- Find the pair with maximum resistance. This is the sum of the resistances of the starting and working windings (the circuit between the starting and working terminals).
- The third contact, which did not participate in measuring the maximum resistance, is common (C).
- Now measure the resistance between the common contact and the other two.
- A pair with the smallest resistance is working winding (R).
- A pair with the largest (of the remaining two) resistance - this starting winding (S).
For example, you got the following values: between contacts A and B - 25 Ohms, between B and C - 15 Ohms, between A and C - 10 Ohms.
The maximum value of 25 Ohms is the sum. This means a contact not participating in this pair (in this example it is C, if we measured A-B, but let's recalculate correctly).
Correct calculation:
Pair 1: 25 Ohm.
Pair 2: 15 Ohm.
Pair 3: 10 Ohms.
The sum of the two smaller ones (15 + 10) is 25. This means that 25 Ohms is the resistance between the Start and Working terminals.
The common terminal is the one that gives 15 and 10 Ohms with the rest.
So, 10 Ohms is the Working winding (lower resistance).
15 Ohms is the Starting winding (higher resistance).
Table of normal resistance values
Knowing the approximate resistance values helps you quickly determine the health of the engine. However, it is worth remembering that the values may vary depending on the compressor power, manufacturer and winding temperature (a cold motor will show less resistance than a hot one). Below are indicative data for popular models.
| Compressor type / Manufacturer | Working winding resistance (Ohm) | Starting winding resistance (Ohm) | Total resistance (Ohm) |
|---|---|---|---|
| Atlant (KSh-50, KSh-60) | 15 – 25 | 30 – 45 | 45 – 70 |
| Indesit / Stinol | 12 – 20 | 25 – 35 | 37 – 55 |
| Danfoss / Secop (low power) | 20 – 35 | 40 – 60 | 60 – 95 |
| Chinese analogues (Jiaxipera, Embraco) | 10 – 22 | 20 – 40 | 30 – 62 |
If your measurements are radically different from the tabular data (for example, they show several hundred Ohms or, conversely, fractions of an Ohm), this signal of a malfunction. It is also important to check the resistance to the housing (between any contact and the copper tube or a cleaned place on the housing). In a working compressor, there should be infinity (one in the high-order digit of the multimeter).
Small deviations of 1-2 Ohms are acceptable. depend on the error of the device and temperature. However, if the resistance of one of the windings is zero, this is a short circuit. If the resistance tends to infinity when the pair is connected, this is a break.
☑️ Compressor diagnostic checklist
Typical faults and their symptoms
Understanding what exactly happened to the windings helps to make the right decision about repairs. There are three main types of electrical faults of the motor-compressor.
Winding break. The multimeter shows infinite resistance (number 1 on the left) on. one of the pairs of contacts where the value should be in Ohms. If the working winding is broken, the compressor will not hum at all. If the starting winding is broken, the motor will hum, but will not start until the thermal protection is triggered.
Interturn short circuit. This is the most insidious defect. 20 Ohm shows 2-3 Ohms. In this case, the current in the winding increases sharply, the compressor hums strongly, the circuit breaker knocks out in the panel, or the wiring burns out. It is difficult to determine the interturn short circuit only by continuity; often a comparison with a known-good motor of the same model is required.
Breakage to the case. An electrical connection appears between the windings and the metal case. The multimeter shows some kind of resistance (not infinity) between the contact and the case. This is fatal to the user and requires immediate replacement of the unit.
⚠️ Attention: If you find a breakdown to the case, operating the refrigerator is prohibited! metal parts of the refrigerator can lead to electric shock, since the body will be energized.
Sometimes there is a situation when the compressor “rings” normally, but does not start. This may indicate a mechanical wedge of the piston group or a malfunction of the start relay, and not a problem with the windings. In such cases, technicians sometimes use a method. "wedging" by applying increased voltage, but this is a job for professionals with the appropriate equipment.
Conclusion and recommendations for replacement
Determining the windings of a refrigerator compressor is a procedure accessible to anyone who knows how to hold a multimeter in their hands. The main thing is to follow the sequence of actions and safety precautions. If measurements show a break or short circuit, repair the windings in the conditions. apartment is impossible due to the tightness of the housing and the need to rewind the stator under special conditions.
In the event of a malfunction, the only solution is to replace the compressor with a similar one. When selecting a new unit, pay attention not only to the geometric dimensions and seats, but also to the refrigerant (freon), power and type of oil. An incorrectly selected compressor can quickly fail or not provide the required performance. cold.
Remember that even a serviceable electrical motor may not work due to problems with the control system. Therefore, before buying a new compressor, make sure that the thermostat, start relay and the integrity of the refrigerator wiring are in good working order.
Is it possible to start the compressor without a relay, directly?
Theoretically, you can start by applying voltage to the working winding and briefly to the starting winding. However, doing this without a protective relay is extremely dangerous. If the compressor does not start the first time or jams, the windings will burn out in a matter of seconds. In addition, without thermal protection, the motor can overheat during operation.
Why does the resistance of the windings change during operation? heating?
The copper from which the windings are made has a positive temperature coefficient of resistance. When heated, the resistance of the metal increases. Therefore, measurements on a hot compressor will always show values higher than on a cold one. For accurate diagnostics, it is better to cool the unit to room temperature.
What to do if the winding resistances are the same?
In some circuits (rarely for household refrigerators, more often for industrial or specific motors) the windings can be made with the same wire. But for standard refrigerators Atlant, Indesit, LG there should be a difference. If the resistances are equal (for example, 20 Ohms), most likely the motor is faulty (an interturn short circuit in one of the windings has changed its parameters) or it is specific. a model that requires studying the technical documentation.
How to distinguish a Chinese compressor from a European one by windings?
It is difficult to distinguish the manufacturer by the electrical parameters of the windings, since the physics of the process is the same. Chinese compressors (Jiaxipera, QD) often have slightly smaller dimensions and can use less. high-quality varnish coating of the wires, which leads to breakdown faster. However, the testing method and resistance ratio (Operating < Starting) remains the same for all asynchronous motors of this type.