A sudden or periodic knocking inside the refrigerator compartment can unsettle any owner of household appliances, especially if the sound is heard in the silence of the night. Many users mistakenly believe that any extraneous noise indicates a critical malfunction and imminent breakdown of an expensive unit. However, in most cases click when turned off is a standard operating process incorporated by engineers into the design of the compressor.
The physics of the refrigeration circuit involves constant changes in pressure and temperature, which inevitably causes thermal expansion and contraction of metal parts. Understanding the difference between natural acoustic phenomena and signals of a real breakdown will help you avoid unnecessary panic and unnecessary expenses on calling a technician. In this article, we will analyze in detail the mechanics of the sounds that occur when the motor stops and learn how to diagnose the condition of the equipment.
Normal operation of the refrigerator is a balance between cooling efficiency and the level of noise produced. If you hear a single or double click at the exact second the motor hum stops, most likely the protection or thermal control system has activated. Let's look at the main reasons why a refrigerator clicks, dividing them into design features and technical faults.
Physics of the process: thermal expansion and contraction
The most common and absolutely harmless cause of cracking and clicking is the physical property of materials. The internal walls of the refrigerator, the evaporator and the circuit tubes are made of metal, which changes its geometric dimensions when the temperature changes. This process is called thermal expansion. When the compressor is running, the tubes cool, and when it stops, they begin to warm up to room temperature.
At the moment when the motor turns off at the command of the thermostat, a sharp change in refrigerant pressure occurs in the system. Metal structural elements that have been compressed by cold begin to rapidly expand. This microscopic shift of metal layers relative to each other causes a characteristic loud click or series of cracks. This is especially often observed in models with No Frostwhere plastic and metal interact during cyclic defrosting.
The intensity of the sound depends on the quality of the assembly and materials. Cheap, thin metal can “sing” and click louder than thick, premium brand steel sheets. The tightness of the tubes to the body also affects: if they are not fixed rigidly, vibration during expansion will be transmitted to the walls of the chamber, enhancing the effect. This is not a breakdown, but only a feature of operation.
Owners should pay attention to the nature of the sound. If these are rare, single strikes, reminiscent of metal cooling in a furnace, then there is nothing to worry about. Over time, when the refrigerator “gets used”, such sounds may become quieter, but they rarely disappear completely. The design must have some play to compensate for temperature deformations, otherwise the metal may burst from stress.
Operation of the start relay and thermostat
The second most common cause of clicking is the electrical part of the refrigerator, namely starting relay. This small mechanism is responsible for starting the compressor engine and protecting it from overloads. It is the relay that makes a loud, clear click when the motor turns on and off. This is the sound of opening or closing electrical contacts inside the relay housing.
If a click is heard at the moment when the refrigerator should start working, but there is no buzz, or the motor hums for a couple of seconds and clicks again, turning off, this is an alarming symptom. In normal operation, the relay clicks once when starting and once when stopping. A frequent clicking sound (every few seconds) indicates that the starter is unable to start the compressor and the thermal protection is tripping.
The thermostat may also make sounds. This is a mechanical device that opens the circuit when a set temperature is reached. Inside it there is a bimetallic plate that bends and switches contacts with a characteristic click. On older models this sound can be quite loud. In modern electronic systems, control is quieter, but mechanical thermostats are still widespread in the budget segment.
It is important to distinguish between a healthy relay click and a pathological one. A healthy sound is a monosyllabic “clack” followed by silence or a steady hum. If you hear a series of quick clicks, reminiscent of the operation of a telegraph key, this indicates burnt contacts or a malfunction of the motor windings. In this case, operating the equipment can be dangerous.
Hydraulic shock and movement of refrigerant
The third reason lies in the very environment that cools your products - refrigerant (freon). A mixture of gases and oil under pressure circulates in the system. When the compressor stops, the pressure in the discharge and suction lines is equalized. This process may be accompanied by sounds similar to the pouring of liquid or dull thuds.
Sometimes so-called water hammer may occur in the condenser or evaporator tubes if the circulation of oil or refrigerant in the system is disrupted. However, most often the sounds heard are simply fluid flowing through the tubes. When the motor stops, the flow of freon stops abruptly, and the inertia of the fluid movement can cause slight impacts on the walls of the tubes or partitions.
⚠️ Attention: If, along with clicks, you hear a hissing, whistling or the sound of water flowing out (which in fact is not there), this may indicate a freon leak. In this case, the refrigerator will stop freezing, and the motor will work without stopping.
Particular attention should be paid to the sounds in refrigerators with the system No Frost. There, the refrigerant circulates according to a more complex pattern, and the presence of fans adds its own acoustic nuances. When the compressor is turned off, the fan also stops, which can create the effect of a fading hum or a final click of the blades stopping.
Mechanical malfunctions of the compressor
The situation becomes more serious if the clicks are associated with mechanical wear and tear on the very heart of the refrigerator - the compressor. Modern units are often equipped inverter linear compressors, which operate differently than older piston models. Linear compressors, for example, can produce specific sounds when the piston rotation speed changes.
If the piston group is worn out, when the engine stops, the piston may hit the valve group due to violation of the clearances. It sounds like a metallic clang or a strong blow. The cause may also be a weakening of the compressor itself to the frame of the refrigerator. The vibration that accumulates over the operating cycle, during a sudden stop, causes the motor housing to shift and hit the cabinet walls.
You can diagnose a problem with the compressor by carefully placing your hand on the refrigerator body at the moment of the click. If you feel strong vibration that turns into shock, or if the sound is accompanied by a burning smell, discontinue use. Further work can lead to complete failure of the unit and expensive repairs.
Myth about inverter refrigerators
It is believed that inverter refrigerators operate silently. This is not entirely true. They are indeed quieter, but when changing power or stopping, they can emit a low-frequency hum or click, which differs from the sound of a conventional relay.
The table below shows the main differences between normal and emergency sounds for quick diagnosis:
| Sound type | Moment of occurrence | Probable reason | Status |
|---|---|---|---|
| Single loud click | Strictly when turning off the engine | Thermal expansion or relay | Normal |
| Frequent clicking sound (like a machine gun) | When trying to start | Malfunction of the starting relay | Repair |
| Thud metal knock | At the end of the operating cycle | Piston impact or loosening of fasteners | Diagnostics |
| Crackling sound similar to breaking ice | Periodically, regardless of the motor | Deformation of plastic (No Frost) | Normal |
The influence of incorrect installation on the sound background
Often the cause of strange sounds is not the internal device, but external factors associated with the installation. If the refrigerator is not level, vibration from the operating compressor accumulates in the structure. At the moment of stopping, this accumulated energy is released, causing the housing to shift and a characteristic knock on the floor or wall.
Check the adjusting supports. They must be unscrewed so that the refrigerator stands stable and does not wobble with a slight push. The gap between the back wall of the refrigerator and the wall of the room also plays a role. If the condenser tubes touch the wall, during thermal expansion they will knock on the plaster or wallpaper.
☑️ Diagnostics of refrigerator installation
Another important aspect - transport bolts. Although they are usually removed during installation, some models still have compressor mounting parts that must be removed. If the compressor “sits” on hard bushings without rubber dampers, any sneeze will produce a loud knock throughout the entire housing.
When it is necessary to call a specialist
Despite the fact that many sounds are natural, there are “red flags” that cannot be ignored. If the clicks are accompanied by the refrigerator refusing to freeze, the appearance of ice in unexpected places, or constant cyclic on-off switching (working in jerks), professional diagnostics are required.
The condition is especially dangerous when, after the click, the smell of burning wiring or plastic is felt. This indicates overheating of the compressor windings or melting of the starting relay insulation. In such a situation, you must immediately disconnect the device from the network and call a specialist. Continuing operation may result in a fire.
⚠️ Attention: Self-repair of the refrigerant circulation system is prohibited without a license and special equipment. If the problem is a freon leak or a capillary line, entrust it to professionals.
It is also worth contacting the service if the refrigerator is more than 10 years old and the nature of the sounds has changed dramatically. Aging of rubber seals, drying out of the oil in the compressor and wear of fan bearings change the acoustic profile of the equipment. Timely replacement of worn-out components will prolong the life of your kitchen assistant.
Prevention and care of the cooling system
To minimize noise and prevent the development of malfunctions, it is important to properly care for the refrigerator. Regular defrosting (for drip systems) prevents the formation of ice plugs, which can cause unnecessary sounds when chipped. In systems No Frost it is important to keep the drainage hole clean.
Do not overload the shelves with products. Heavy objects can increase the vibration of shelves and glass partitions, creating resonance with the sounds of the compressor. Make sure that the food does not touch the back wall of the chamber, especially in the evaporator area, so as not to create unnecessary noise from freezing and thawing.
Periodically check the tightness of the door. If the seal is worn out, the compressor will work more often to compensate for the loss of cold. This will lead to more frequent relay clicks and accelerated wear of the starting equipment. Replacing the seal is a simple procedure that will significantly reduce the load on the unit.
The secret of silence
Some users place special anti-vibration mats or pieces of thick rubber under the legs of the refrigerator. This dampens the vibration of the housing and makes the clicks of the compressor less audible to the human ear.
Frequently asked questions (FAQ)
Why does the refrigerator click but does not turn on?
This is a classic sign of a malfunction of the start relay or the compressor itself. The relay tries to start the motor, a click is heard, but due to an interturn short circuit or jamming of the piston, the start does not occur, and the protection opens the circuit again. The relay needs to be replaced or the compressor repaired.
Is it normal for a new refrigerator to click?
Yes, absolutely normal. New materials can be stiffer and produce louder sounds when thermally expanding. Besides, you just started paying attention to it. After a few weeks of operation, the sounds may become quieter or more familiar to the ear.
Can a refrigerator click due to power surges?
Indirectly - yes. If the network voltage is unstable, the protection relay may frequently operate, turning off and on the power to the compressor, which is accompanied by clicking sounds. It is recommended to use a voltage stabilizer to protect expensive equipment.
Why are clicks heard only at night?
During the day, background noise (conversations, TV, street) masks the quiet sounds of equipment operation. At night, in silence, even the standard clicks of the thermostat and the expansion of metal become clearly visible. This is a feature of the acoustics of the room, and not a breakdown.
Is it dangerous to ignore loud clicks?
If the clicks are loud, metallic and accompanied by vibration of the case, it is dangerous to ignore it. This can lead to destruction of the compressor mounts or breakdown of the windings. It’s better to play it safe and call a professional for diagnostics.