The situation when the compressor in the refrigerator suddenly stops working always causes panic, and this is quite understandable. It is this unit that is the “heart” of the cooling system, and without its hum, the temperature in the chamber quickly begins to rise, threatening the safety of the products. However, before calling a technician or looking for a new device, it is worth analyzing the situation, since the silence of the motor does not always mean its final breakdown.
In some cases, the compressor is working, but cannot start due to external factors or failures in the control electronics. Understanding the system and the basic principles of its operation will help you save time and money by avoiding unnecessary expenses on replacing expensive components. In this article, we will analyze in detail all possible causes of failure, from simple power surges to complex technical faults.
Primary diagnostics: why is the motor silent?
The first thing to do if you notice that the compressor does not turn on is to carry out initial visual and auditory diagnostics. Often the reason lies not in the engine itself, but in a lack of power or a security system blocking the start. Check to see if the light inside the chamber comes on when you open the door, as this will indicate that there is voltage present.
If the lights on the control panel (if any) do not light up, the problem may be with the surge protector, the outlet, or a damaged power cord in the refrigerator. In cases where there is light, but the motor does not make any sounds, it is worth listening: sometimes you hear a quiet click or hum that ends abruptly. This is an important signal that starting relay is trying to start the engine, but is encountering resistance.
It is also worth paying attention to the room temperature. If the refrigerator is in an unheated garage or on a balcony at a temperature below +5°C, the compressor may not start due to the oil solidifying or the way the thermostat operates in cold conditions. In such cases inverter models may behave differently than classic linear units.
Problems with the start-up relay and thermostat
One of the most common reasons why the compressor does not work is failure of the start-protection relay. This small element is responsible for supplying a starting pulse to the motor winding and protecting against overloads. If the relay is “stuck” or burnt out, the circuit does not close, and the motor remains motionless, despite the serviceability of the compressor itself.
The second important element of the control circuit is the thermostat (thermostat). It is he who gives the command to turn on the cooling when the temperature in the chamber rises above the set one. If the thermostat contacts have oxidized or the sensor has failed, the signal simply does not reach the engine. In modern models with electronic control, this function is performed by thermal sensorwhich can also fail.
⚠️ Attention: Before replacing the relay or thermostat, be sure to unplug the refrigerator! Working with live electrical components is deadly.
To check the relay, you often have to remove it and gently shake it: if a ringing sound is heard inside, it means the mechanism is damaged and requires replacement. The thermostat is checked by testing the contacts with a tester or by temporarily shorting its wires (for diagnostics), but this method requires caution.
How to check the relay yourself?
To check the relay, remove it from the compressor. Shake the device near your ear. If a rattling sound is heard, it means the internal contact group is broken. Also inspect the contacts for carbon deposits or melting. If the relay is electronic, visual diagnostics may not yield results, and a replacement with a known good one will be required.
Faults of the compressor itself: motor or mechanics?
If the control electronics and relay are working properly, suspicion falls on the engine itself. The compressor may not work for two main reasons: electrical (the winding is burned out) or mechanical (the piston group is jammed). In the first case, the engine hums, but does not start, or is completely silent if there is an open circuit.
Mechanical compressor wedge is a serious problem, often arising due to oil burnout or moisture entering the system. The pistons get stuck in the cylinders, and the engine is physically unable to make the first push. Attempts to start such a unit with a “push” or an increase in voltage can lead to complete destruction of the engine and even fire of the wiring.
It is worth noting that modern ones inverter compressors (for example, in LG or Samsung refrigerators) are more complex. They do not have a classic start relay, and their diagnosis requires a special tester. If such a motor does not start, the control unit (inverter board) is often to blame, and not the engine itself.
☑️ Compressor diagnostics
Refrigerant leak and pressure problems
Sometimes the compressor is working properly and even tries to work, but the protection system turns it off almost immediately after startup. This is a classic symptom of a freon leak. When the refrigerant in the system becomes critically low, the compressor runs “idle” without creating the necessary pressure, which leads to its overheating and thermal protection.
Visually it is difficult to notice a leak, since freon is a colorless and odorless gas. However, indirect signs may include swelling on the rear radiator grille or oily spots at the joints of the tubes. If you see that the motor turns on for 10-20 seconds, hums, and then there is a click and silence sets in, most likely it is a lack of refrigerant refrigerant shortage.
It is important to understand that you cannot simply “add freon” to a system with a leak. First you need to find the place of damage, solder it, evacuate the system and only then fill it with new gas in a strictly defined amount. It is impossible to do this on your own without equipment.
| Symptom | Probable cause | Necessary actions |
|---|---|---|
| Motor hums for 5-10 seconds, clicking, silence | Leakage freon or compressor wedge | Call a technician to find a leak |
| Complete silence, there is light in the chamber | Malfunction of the thermostat or relay | Replacing the start relay or sensor |
| There is a hum, there is no cold for a long time | Clogged capillary tube | Cleaning the system and replacing the filter |
| The motor is hot, but does not start | Interturn short circuit windings | Replacing the compressor |
Clogged capillary tube and filter drier
Another technical reason for failure of normal operation may be a clogged capillary tube or filter-drier. In the freon circulation system, plugs may form from oil or ice breakdown products (if there is moisture in the system). This creates excess pressure that the compressor cannot cope with.
As a result, the motor operates with overload, gets very hot and switches off due to thermal protection. A characteristic sign of a blockage is that the condenser (grid at the back) may only be hot at the beginning or, conversely, remain cold, although the motor is running. There may also be swelling of the walls of the refrigerator where the pipeline is laid.
Eliminating this problem requires qualified intervention. The technician will have to depressurize the system, purge the tubes with nitrogen under high pressure, replace the filter drier and refill the refrigerator. Attempts to “break through” the blockage by increasing the voltage are dangerous and ineffective.
Electronic failures and control module
In modern refrigerators with a system No Frost and electronic control, the main control module is responsible for turning on the compressor. Voltage surges in the network, moisture ingress or manufacturing defects can damage the triac or other elements of the board that control the motor.
In such cases, the compressor may be fully operational, but the start command is simply not received. Diagnostics requires checking the output voltage at the terminals going to the motor. If, at a set low temperature, there is no voltage at the output from the board (or it is incorrect), the problem lies in the “brains” of the refrigerator.
Sometimes a complete system reset helps: disconnecting the device from the network for 15-20 minutes. This allows the electronics to reset and clear erroneous statuses. If, after connecting to the network, you hear a characteristic click of the relay on the board, but the motor does not respond, it is worth checking the integrity of the wires going from the board to the compressor.
⚠️ Attention: Electronic modules are sensitive to static electricity. Do not touch the board contacts with bare hands without an antistatic wrist strap.
When is it necessary to call a professional technician?
Independent repair is possible only in cases of replacing the start relay, thermostat or checking the integrity of the wiring. All manipulations associated with a sealed circuit (filling with freon, soldering tubes, replacing a compressor) require special equipment and a license.
In addition, incorrect refrigerant charging or use of the wrong oil can completely kill a new compressor in a matter of minutes. The technician also has the skills to search for micro-leaks that cannot be detected visually or audibly.
If you determine that the problem is not in the socket or relay, and the diagnostics indicate a leak, wedge or burnt out windings, the best solution would be to contact a service center. This guarantees not only the quality of the repair, but also the safety of using the device in the future.
Is it worth replacing the compressor on an old refrigerator?
If the refrigerator is more than 10-12 years old, replacing the compressor may not be economically feasible. The cost of a new motor, a technician’s work and refilling with freon often amounts to 50-70% of the price of a new refrigerator.
Why is the compressor hot, but the refrigerator does not freeze?
This indicates that the motor is working, but the refrigerant is not circulating through the system. Reasons: freon leak, clogged capillary tube or malfunction of the compressor itself (does not create compression). Diagnostics by a specialist is required.
Is it possible to start the compressor directly, bypassing the relay?
Theoretically, it is possible by applying voltage directly to the working and starting windings, but this is dangerous and requires precise knowledge of the circuit. In addition, without a starting relay, the motor may burn out the next time it is started. This is a diagnostic method, not a repair.
How much does it cost to replace a compressor on average?
The price consists of the cost of a new unit, soldering work, vacuuming and refilling with freon. On average, this ranges from 4,000 to 8,000 rubles depending on the model of the refrigerator and the region, but only the technician will give the exact amount after an inspection.
The compressor is humming, but does not start - what to do?
Most likely, the problem is in the start relay (contacts are stuck) or a mechanical wedge of the piston group. Try knocking on the relay housing or replacing it. If it doesn’t help, you need a technician.
Does the temperature in the room affect the start of the compressor?
Yes. If the room is too cold (below +5°C), the oil in the compressor thickens and it may not start. If it is too hot (above +35-40°C), the motor may overheat and go into protection faster than usual.