A sudden stop in the operation of the refrigerator or, conversely, its endless hum without cooling is always stressful and the risk of food spoilage. In most cases, the culprit of the malfunction is the heart of the unit - compressor, which is responsible for the circulation of refrigerant in the system. However, before calling a technician or buying new equipment, it is worth conducting an initial diagnosis yourself in order to understand the scale of the problem and the approximate cost of restoration.
Modern refrigerators, be they classic models Atlant, Indesit or inverter systems LG i Samsung, have a similar logic for the operation of the engine compartment. Understanding the basic principles of electrics and the design of the motor will allow you to determine with a high degree of probability whether the compressor is alive or is it time to change it. The main thing in this process is not to panic and strictly follow safety precautions when working with electrical appliances.
In this article we will analyze a step-by-step algorithm of actions that will help you Check the integrity of the windings and exclude a short to the housing without using complex laboratory equipment. You will learn how to use a multimeter correctly, what to look for during a visual inspection and what signs will indicate that the unit is “jamming” or has completely burned out.
Primary diagnosis: visual inspection and analysis of symptoms
Before you take on tools, it is necessary to conduct a thorough external analysis of the situation. Often the nature of the noise or its absence can tell more about the condition of the compressor than complex measurements. If the refrigerator hums, but does not cool, or turns on for a couple of seconds and immediately clicks when turning off, these are classic symptoms of problems with starting the engine or its mechanical part.
Carefully inspect the back wall of the unit. You should not be interested only in the pipes; pay attention to the black “barrel” of the compressor itself. There should be no obvious traces of oil, soot or soot, which may indicate gasket failure or overheating. Also check the integrity of the wires going to the motor: melted insulation is a sure sign of a short circuit or network overload.
- 🔊 A characteristic click when trying to start and silence after it often indicates a malfunction of the starting relay or jamming of the piston group.
- 🔊 An even but quiet hum without cooling may mean that the compressor is working, but there is no freon in the system due to a leak.
- 🔊 Complete absence of sounds when the refrigerator is plugged in indicates a broken power circuit or a burnt winding.
Do not forget that Some modern equipped models with inverter motors operate almost silently. In such cases, you cannot rely only on hearing, and a deeper instrumental check of the electrical parameters will be required.
Necessary tools and safety measures
For high-quality diagnostics, you will need a minimum set of tools, which can often be found in a home mechanic’s drawer. The key device is multimeter (tester), which allows you to measure resistance and check circuits for breakdown. Without this device, the check will be only approximate and will not give an accurate answer about the condition of the windings.
⚠️ Attention: Carry out all manipulations with the electrical part of the refrigerator only with the power completely disconnected from the network! Unplug the cord from the outlet before removing the back panel.
In addition to a multimeter, prepare a flathead and Phillips screwdriver to remove the protective casing above the compressor. You may also need pliers to carefully remove the terminals and electrical tape to mark the wires if you plan to disassemble the connections. You should work in a dry room to eliminate the risk of electric shock from residual charge or accidental switching on.
It is important to understand the design of the unit: a power cable is connected to the compressor, which is divided into three contacts that go to the starting relay. It is these contacts that we will “call”. If you do not have experience working with electrical appliances, it is better to limit yourself to a visual inspection and call a specialist, since careless handling of the wires can lead to damage to the control board.
Removing the start relay and access to the contacts
To get to the compressor contacts, you need to remove the plastic or metal casing covering the back of the motor. It is usually secured with latches or screws. After removing the protection, you will see a cylindrical or conical block - this is starting relay, which is placed directly on the compressor terminals.
Carefully remove the relay. In older models it can simply be removed by hand, in new ones it can be held on by a bracket or latch. Don't pull the wires! Grasp the relay housing and, gently rocking it from side to side, pull it down. Under the relay you will see three metal pins arranged in a triangle - these are the terminals of the compressor windings.
- 🔌 The upper contact (often one) is usually common or working, depending on the circuit.
- 🔌 The bottom two contacts are responsible for the starting and working windings, respectively.
- 🔌 The fourth contact (if any) can be used for thermal protection or case grounding.
Before checking, it is advisable to photograph the location of the wires or mark them with a marker, so as not to confuse the polarity during assembly. Although in most household compressors it is difficult to reverse the phases due to the design of the relay, the procedure is important to maintain a guarantee for the work performed.
☑️ Preparation for diagnostics
Checking the compressor with a multimeter: measuring resistance
The most reliable way to check is measuring resistance windings Switch the multimeter to resistance measurement mode (limit 2 kOhm or 200 Ohm). First you need to find common terminal. To do this, attach one probe to any upper contact, and the second to the lower ones in turn. The pair of contacts that showed the least resistance will indicate the working winding, and the remaining third contact will be common.
In normal conditions, the resistance between the terminals should be within certain limits. Between the common and working terminals it is usually 10–30 Ohms, and between the common and starting terminals it is usually 20–50 Ohms. The total resistance between the starting and operating terminals should be equal to the sum of these two values. If the device shows “infinity” (one on the left of the screen), then there is a break in the winding and the compressor is faulty.
Pay special attention to checking for breakdown on the housing. Switch the multimeter to the “continuity” mode or resistance measurement to the maximum limit (2 MOhm). Touch one probe to the cleaned area on the compressor housing (where there is no paint), and the other to each of the three contacts in turn. The device should be silent and show infinite resistance. Any squeak or resistance reading indicates that the winding has shorted to the housing, and it is strictly prohibited to operate such a unit For inverter models, the procedure may differ, since they have more complex electronic filling inside the motor. In such cases, a standard test with a multimeter may not be informative enough, and a connection via a special service adapter is required..
For inverter models, the procedure may differ, since they have more complex electronic filling inside the motor. In such cases, a standard test with a multimeter may not be informative enough, and a connection via a special service adapter is required.
Normal resistance values
For different models of refrigerators, the values may differ. For example, for Danfoss NL10FN compressors, the norm is 22-25 Ohms between the working and common windings, and 40-45 Ohms between the starting and common windings. A significant deviation (more than 20%) indicates an interturn short circuit.
Table of typical faults and their symptoms
The table below will help to systematize the data obtained. By comparing the symptoms and measurement results, you can more accurately determine the cause of the breakdown. Remember that a combination of several signs increases the likelihood of a diagnosis.
| Symptom | Multimeter readings | Probable cause | Solution |
|---|---|---|---|
| Clicks and goes out | Resistance is normal | Starting relay is faulty | Replacement of relay |
| Buzzing, does not start | Resistance between contacts 0 Ohm | Interturn short circuit | Replacing the compressor |
| Silence, no reaction | Infinite resistance (break) | Breakage of winding or thermal protection | Replacing the compressor |
| Knocks out the machines | Resistance to the case (beeps) | Insulation breakdown on the case | Urgent replacement |
If the multimeter shows values are close to normal, but the refrigerator still does not work, the problem may lie not in the electrics, but in the mechanics. For example, the piston could jam or the crankshaft liner could rotate. In such cases, the engine hums, consumes high current, but the shaft does not turn.
Checking the starting relay and thermal protection
Often the compressor itself is working, but the problem lies in the attachment. Start relay responsible for supplying an impulse to the starting winding at the moment of start. Inside the plastic case there is a coil and a movable core. If the contacts inside the relay are oxidized or burnt, the current will not pass and the motor will not start.
Thermal protection (thermal relay) serves as a fuse. It opens the circuit when the compressor overheats. It’s easy to check: test the thermal protection contacts with a multimeter. There should be a "squeak" or reading close to zero. If the circuit is broken even on a cold engine, the protection is faulty and requires replacement.
- 🛠️ Shake the relay next to your ear: if you hear the sound of broken glass or loose parts, it is definitely faulty.
- 🛠️ Inspect the contacts inside the relay: black soot indicates poor contact and sparking.
- 🛠️ Check the integrity of the bimetallic thermal protection plate for deformation.
Mechanical check: test with a pressure gauge
If the electrical part is in order, but there is no cold, the compressor may have lost performance. This happens when the valves or piston group wear out. For verification you need pressure station. It is connected to a process fitting (usually a copper tube with a sealed end, which must be carefully filed or pierced with a needle).
When a working compressor is turned on, the pressure in the discharge system should increase quickly. If the pressure gauge needle stands still or rises very slowly, it means that the compressor does not hold pressure. At home, without a vacuum gauge and scales for freon, it is difficult to fully check this parameter, so the diagnosis is often made by exclusion: the electrical system is intact, the relay is new, there is freon (no leaks in the pipes), but there is no cold - which means the compressor needs to be replaced.
⚠️ Attention: Independent refilling with freon and working with an open circuit require a license and special equipment. If you find a leak or need to evacuate the system, it is better to entrust further work to professionals.
It is also worth considering that technical characteristics and requirements for refrigerants may vary depending on environmental standards and models. Always check the manufacturer's technical documentation for your specific refrigerator modification before tampering with the refrigerant circuit.
Frequently asked questions (FAQ)
Is it possible repair a burnt-out compressor yourself?
Rewinding the windings at home is impossible due to the need for special varnish, precise balancing and tightness. If the winding is burned out or there is an interturn short circuit, the compressor must only be replaced with a new one.
Why may the new compressor not start after replacement?
The reason may be the installation of an incorrect start relay, contamination of the system with combustion products of the old motor (thorough purging with nitrogen is required) or lack of grounding, which causes the board control blocks the start.
How long does a compressor in a refrigerator last on average?
The average service life of modern compressors is 10–15 years. Inverter models, operating without constant stopping and starting, theoretically last longer, up to 20 years, but are more sensitive to power surges in the network.
Is it dangerous to turn on a refrigerator with a faulty compressor?
Yes, it is dangerous. A breakdown on the housing can lead to an electric shock when touching the metal parts of the refrigerator. In addition, constant attempts to start a burnt-out motor can damage the wiring in the apartment or damage the control board.