The lack of cold in the chamber often becomes an unpleasant surprise, especially when there are perishable products inside. If you notice that the unit is humming but not cooling, or, conversely, is standing in complete silence, the first suspicious object is the motor. Diagnostics of the compressor - this is a key stage that allows you to understand whether it is worth undertaking complex repairs or whether it is easier to replace the entire unit. In most cases, the problem lies precisely in the heart of the refrigeration system.
Before grabbing the tools, it is necessary to conduct an initial visual inspection and rule out simple causes. Often, equipment owners begin to panic due to the lack of cold, forgetting to check the tightness of the door or the integrity of the power cord. However, if the light in the chamber is on, and the motor is silent or makes strange clicks, you will have to look deeper. Electrical diagram The refrigerator is designed so that if there is an open circuit or short circuit, the protection can turn off the power, simulating a motor breakdown.
In this article we We will analyze in detail the algorithm of actions that will help you identify the problem yourself. You do not need complex factory equipment, just a basic set of home craftsman and an understanding of the principles of electrical engineering. The normal resistance of the windings of a working compressor is usually in the range from 20 to 45 Ohms, and any strong deviation from these values signals a problem. Let's start from the very beginning and go through this path step by step.
Primary signs of motor failure
Symptoms of compressor failure can be obvious or hidden. In the first case, you hear a loud bang, after which the refrigerator goes silent forever. In the second, the unit tries to start, hums for a few seconds, then the relay clicks, and the process repeats cyclically. This is a classic sign that starting relay the engine cannot start, or the engine itself is jammed. Such signals cannot be ignored, since constant attempts to start can lead to burnout of the wiring.
There is a more insidious type of breakdown when the compressor runs continuously without turning off. In this case, the temperature in the chamber may be normal or slightly elevated, but the walls of the refrigerator will be hot. This indicates that performance has fallen: the piston group is worn out, and the compressor simply drives freon in a circle without creating the necessary pressure. It is impossible to check this by ear; measurements are needed.
⚠️ Attention: If you smell burnt insulation or see sparking in the compressor area, immediately unplug the refrigerator. Further operation in this condition may lead to a fire.
It is also worth paying attention to the temperature of the motor housing. If during operation it heats up to a state where it is impossible to touch it with your hand (more than 90 degrees), this is an alarming sign. A working unit should be hot, but not red-hot. Excessive heating often indicates an interturn short circuit in the windings or a violation of the heat sink.
To systematize the symptoms, the main groups of problems can be distinguished:
- 🔇 The motor is completely silent, although the indicators are on.
- 🔊 A hum, clicking is heard, but does not start is happening.
- 🔥 The compressor works non-stop and gets very hot.
- ❄️ The refrigerator is cold poorly, the motor runs in cycles.
Necessary tools and safety measures
Before starting disassembly, you need to prepare the workplace and tools. You will need a multimeter (tester) capable of measuring resistance and testing circuits. This is the main device, without which it is electrical diagnostics impossible. Screwdrivers, pliers and electrical tape will also come in handy. If you plan to remove the compressor, you will need a vacuum pump and a bottle of freon, but a multimeter is enough for the initial check.
Safety comes first. Working with live electrical appliances is life-threatening. All manipulations to connect wires and check contacts should be carried out only with the power cord disconnected from the network. Even capacitors in the circuit can retain a charge, so let the equipment stand turned off for at least 10-15 minutes before starting work. Rubber gloves They will become additional protection, although the sensitivity of your fingers is more important when working with small electronics.
Pay special attention to the integrity of the wire insulation. If you find melted areas or cracks, they must be replaced or carefully insulated before applying voltage. Using damaged wires may result in a short circuit and electric shock. In addition, make sure that the floor under the refrigerator is dry to eliminate the risk of electrical shock through moisture.
☑️ Check readiness for repair
Dismantling and access to the electrical part
To get to the insides of the compressor, you need to remove the protective casing. It is usually located at the bottom of the back wall of the refrigerator and is secured with bolts or plastic clips. Carefully unscrew the fasteners and remove the box. Inside you will see a black barrel - this is the compressor, and on the side or top of it is a smaller plastic box. This start-protective relay.
Remove the relay carefully. It can be fixed with a bracket or simply sit tightly on three contacts. Note or photograph the position of the wires before disconnecting them. Color markings may vary between manufacturers, such as Indesit, Atlant or LG, so a photograph will be your best guide during assembly. Typically, three wires from the compressor and two from the network (phase and zero) are suitable for the relay.
After removing the relay, at the end of the compressor you will see three contacts arranged in a triangle. They are the outputs of the windings. In some models, the contacts may be covered with additional insulation or have a specific shape. It is important not to damage them when cleaning, since oxidation of the contacts can also cause poor contact and false diagnosis of a malfunction.
Checking the start relay and thermostat
Often the culprit behind the silence of the refrigerator is not the motor itself, but its “assistant” - the starting relay. Inside this small device there is a coil and a movable core, which, when voltage is applied, closes the starting winding. Over time, the contacts may burn and the coil may burn out. You can check the relay visually (for the presence of burning) and using a multimeter in continuity mode.
If the relay is working properly, you need to check the thermostat circuit. It is he who gives the command to turn on the compressor when the temperature rises. To eliminate its malfunction, you can temporarily close the thermostat contacts directly. If after this procedure the refrigerator “came to life” and started, it means that the problem was in the temperature sensor, and not in the motor. However, you cannot operate the equipment for a long time without a thermostat.
The table below shows the main components that need to be checked before diagnosing the compressor itself:
| Component | Function | Fault symptom | Check method |
|---|---|---|---|
| Start relay | Engine starting | Clicks, no start | Coil continuity, visual inspection |
| Thermoregulator | Temperature control | The refrigerator does not turn on | Closing the contacts directly |
| Defrost button | Emergency shutdown | Open power circuit | Button ringing |
| Power cord | Power supply | Complete lack of response | Input voltage measurement |
⚠️ Attention: When checking the relay, remember that some models are disposable and cannot be repaired. If soot or melted plastic is visible inside, it is better to replace the part with a new one.
Diagnostics of windings with a multimeter
Now we move on to the most important thing - checking the motor windings. The compressor contact assembly usually has three terminals. Two of them are the ends of the working and starting windings, and the third is common. To understand where it is, you need to call them among themselves. Find the pair of contacts that gives the least resistance - this is the working winding. In parallel to it (through the third contact) there is a starting winding, the resistance of which is always higher.
Take a multimeter, switch it to resistance measurement mode (Ohm) and apply the probes to the contacts. Normal values for the resistance of the working winding are 10-15 Ohms, the starting winding is 20-35 Ohms. The total resistance between the extreme contacts must be equal to the sum of the resistances of each winding separately. If the device shows infinity (break) or zero (short circuit), it means the winding has burned out..
A special case is an interturn short circuit. In this mode, the winding resistance may be normal, but the engine will get very hot and knock out the circuit breaker. It is difficult to identify such a malfunction with a multimeter; it is often necessary to replace the compressor based on indirect signs (heating, humming). Also be sure to check the “breakdown on the housing”: place one probe on the cleaned metal part of the compressor housing (where there is no paint), and the second one in turn to the contacts. The device should be silent. If current flows, the compressor is dangerous to use.
What is an interturn short circuit?
This is a violation of the insulation between the turns of copper wire inside the winding. Because of this, some of the turns fall out of operation, the current increases, the motor overheats and hums. The multimeter may show the norm, but the motor will not work correctly.
Checking for “wedges” and mechanical faults
Electrical serviceability of the windings does not guarantee the operation of the refrigerator. The mechanical part - pistons, cylinders, shafts - may be jammed. This happens if the refrigerator has been idle for a long time, or due to oil production. If, when voltage is applied (short-term!), the motor hums and jerks, but does not start, it may be jammed. In some cases, the so-called “wedging” by applying increased voltage helps, but this is a job for professionals.
Mechanical wear also manifests itself in the form of a metallic knock or rumble during operation. If the compressor works but does not create pressure (you can check by disconnecting the discharge tube and feeling the air pressure with your finger), then the piston group is worn out. In this case, replacing the compressor is the only way out, since repairing a sealed unit is not economically feasible.
It is important to note that a wedge can also be caused by a lack of refrigerant. If there is a leak in the system, the compressor pumps vacuum, cooling of the windings with freon stops, and the motor overheats, going into protection. Therefore, before replacing the motor, make sure that the circuit is sealed and filled with gas.
Replacing the compressor: is it worth doing it yourself?
If the diagnostics show that the compressor is faulty, the question arises of replacing it. Theoretically, you can replace the “barrel” at home if you have the skills to solder copper pipes and a vacuum pump. However, the process requires strict adherence to technology: nitrogen purging, humidity control, precise refilling with freon. An error at any stage will lead to rapid breakdown of the new compressor or the formation of an ice plug in the capillary.
In addition, modern refrigerators often use inverter compressors, which are controlled by complex electronics. Simply replacing such a motor with an analogue from an old refrigerator will not work - you need to resolder the control board or install a universal unit, which only a specialist can do. Conventional linear compressors are easier to replace, but the risk of making a mistake when soldering remains high.
If you do not have special tools and experience working with refrigeration equipment, it is better to entrust the replacement to professionals. The cost of the work is often comparable to the cost of a new compressor, but you receive a guarantee that the system is tight and properly charged. In this case, independent repairs may be more expensive due to damage to expensive components.
Is it possible to start the compressor directly without a relay?
Yes, you can start the motor directly by applying 220V to the working winding and briefly to the starting winding. However, this must be done extremely carefully and no longer than 2-3 seconds, otherwise the winding will burn out. This method is used only for diagnostics, but not for permanent operation.
Why does the new compressor get hotter than the old one?
Modern models often have a higher case temperature during operation due to changes in the design and refrigerants used. If the temperature does not exceed 90 degrees and the refrigerator freezes, this is normal.
What resistance is considered normal?
It is considered normal if the resistance of the starting winding is 1.5-2 times higher than the resistance of the working one. The main thing is the absence of a short circuit to the body and the absence of an open circuit.