A sharp or repeated knock in the refrigerator can turn a comfortable stay in the kitchen into a test for nervous system. Often this sound appears suddenly when the equipment has been working flawlessly for years, and immediately raises concerns about the safety of the products and expensive repairs. Understanding the nature of the occurrence of extraneous sounds is the first and most important step to solving the problem, allowing you to avoid panic and unnecessary expenses.
The noise background of a working unit consists of many factors: from the natural physical processes of expansion of materials to critical breakdowns of components. In this article we will analyze in detail why there is a knock in the refrigeratorhow to distinguish normal operation from a malfunction and what measures you can take yourself, without resorting to the help of a specialist.
Natural sounds: the physics of the operation of the refrigeration chamber
Not everyone a knock or click indicates a breakdown. Modern and even old models of refrigerators produce a number of sounds during operation that are determined by physical laws. One of the most common phenomena is thermal expansion and contraction of materials. The plastic of the inner walls, metal tubes of the evaporator and even the housing can make sounds resembling crackling or short knocks when the temperature changes.
These sounds are most often heard immediately after the compressor is turned on, when active cooling begins, or after it is turned off, when the temperature begins to rise. If you hear rare, single clicks or crackling sounds that sound like metal cooling, there's most likely nothing wrong with your appliance. This is especially typical for models with a system No Frost, where temperature changes are sharper.
The sound of flowing liquid is also considered normal. The coolant circulating through the system may gurgle or hiss, especially when the engine is stopped. This indicates that freon continues to move through the tubes under the influence of inertia and pressure differences. It is important to learn to distinguish between these background noises and mechanical shocks that indicate a problem.
⚠️ Attention: If the nature of the sound has changed sharply, and loud metallic clangs have been added to the usual hum, this is a reason for a more careful diagnosis, even if the food has not yet deteriorated.
To reassure and check, you can do a simple test. Try placing your hand on the side of the refrigerator when the sound occurs. If you feel a slight vibration that matches the rhythm of the noise, but the sound is dull, then this is probably just the work of internal processes. However, if the vibration radiates to the floor or the housing makes a loud knock, the reason may be due to incorrect installation.
Problems with installation and vibration of the housing
One of the most commonplace, but common causes of knocking is incorrect installation of the unit. If the refrigerator is not level, the load on the compressor is distributed unevenly, which causes increased vibration. The vibrating case begins to come into contact with walls, furniture or internal elements, generating a rhythmic knocking.
The first thing to do is to check the horizontal installation. Use a building level or even a simple glass of water. The legs of the refrigerator must be unscrewed so that the unit stands stable and does not wobble with a slight push. Often, knocking occurs due to the fact that the refrigerator touches the back wall of the radiator or the side of the kitchen unit.
- 🔨 Check the gap between the back wall of the refrigerator and the wall: it should be at least 5-7 cm for free air circulation.
- 🔨 Inspect the space around: perhaps a chopping pan is leaning against the body board or bottle that begins to rattle from vibration.
- 🔨 Make sure that inside the chamber the shelves and products do not touch the walls and cannot move when the compressor is running.
Another source of noise is loose elements inside. Glass shelves, if they do not have reliable latches, may bounce when the motor starts. Plastic vegetable crates can also bang against the guides if they are not fully inserted or are overloaded.
Diagnostics of compressor malfunctions
If external factors are excluded, and the knocking continues, most likely the problem lies in the heart of the refrigerator - the compressor. This is a complex electromechanical unit that builds up pressure in the system. A healthy compressor operates with a uniform hum, but when parts wear out, extraneous sounds may appear inside it.
One of the common causes of knocking is wear of the internal valves or piston group. In this case, the knock is usually metallic, loud and accompanied by a decrease in cooling efficiency. The compressor may work jerkily, trying to build up pressure, but due to the loss of valve tightness, this is difficult for it.
Also, a knock can be produced start relay, which is responsible for starting the engine. If the relay contacts have oxidized or the mechanism is stuck, you will hear a loud click when you try to start, followed by a buzzing sound, and then another shut-off click. The cycle may be repeated several times until the compressor starts or goes into protection.
⚠️ Attention: If you hear a loud knocking sound inside the compressor when it is running, this may indicate a damaged engine mount. Further operation in this mode will lead to broken tubes and complete failure of the unit.
How to check the compressor without disassembling?
For initial diagnostics, you can use the exclusion method. Unplug the refrigerator, move it away and gently rock it. If you hear a clear knocking noise from internal parts (as if something is loose), this is a bad sign. Also pay attention to the temperature of the compressor housing: if it heats up unevenly or too much, this indicates overload.
It is important to note that inverter compressors, which are found in modern models LG, Samsung or Boschare quieter, but their diagnosis is more difficult. They do not have a classic start relay, so characteristic clicks at start are not typical for them. Any knocking sound in the inverter motor is almost always a sign of a faulty bearing or control board.
Fan noise in No Frost systems
In refrigerators with the system No Frost the fan is responsible for circulating cold air. Over time, its bearings may wear out, or ice may freeze on the blades, causing imbalance and noise. The knocking in this case is usually rhythmic, frequent and resembles the operation of an old fan.
If the fan touches frozen ice with its blades, the sound will be similar to a crackling sound or frequent impacts of plastic blades on a solid obstacle. This often happens if the door seal is broken or if the refrigerator is too close to the wall, which interferes with heat transfer and causes excess condensation to form, which then freezes.
Diagnosing this problem often requires removing the back panel in the freezer. However, before this, you can try to defrost the refrigerator completely, leaving it turned off for 10-12 hours. If after defrosting the knocking noise disappears and appears again after a few days of operation, then the problem is ice freezing on the fan or a malfunction of the defrosting system.
- ❄️ Check the cleanliness of the fan blades: there should be no ice or foreign objects on them.
- ❄️ Assess the condition of the bearing: when rotating the shaft manually The fan should spin easily and silently.
- ❄️ Make sure that the impeller is not cracked or deformed, as this causes beating.
Extraordinary sounds during defrosting and operation of the heating element
In refrigerators with an automatic defrosting system, the heating element (TEN) is periodically turned on to melt the ice on the evaporator. At this moment, you can hear a characteristic hissing or crackling sound. This is the sound of melting ice and dripping water that falls on a hot heating element or pan.
However, if you hear loud clicking or banging noises just when the compressor is turning off and defrosting is supposed to begin, this may indicate a faulty defrost sensor or timer. A mechanical timer makes a distinct click when switching modes, which is normal, but if this sound is accompanied by a knock, the mechanism may be jammed.
It is also worth paying attention to the water collection pan located above the compressor. During active defrosting, water flows into this pan. If the pan is not securely fastened or is deformed, the water jet can cause it to vibrate and knock against the compressor housing. This is especially noticeable at quiet times of the day.
In some models, for example, in old Soviet refrigerators ZIL or Biryusa, the defrosting system may be implemented differently, and the sounds may be louder due to the design features of the capillary tube that passes through the freezer.
Diagnostic table: determine the source of the sound
For ease of systematization of acquired knowledge and quick diagnostics, use the table below. It will help to compare the nature of the sound with the probable cause and the necessary action.
| Character of the sound | Probable cause | Urgency of repair | Actions |
|---|---|---|---|
| Rare clicks, cracking | Thermal expansion of materials | Not required | Observation, this is normal |
| Loud metallic clanging | Wear of the compressor or suspension | High | Call a technician, prepare for replacement |
| Rhythmic crackling/rustling | The fan touches the ice | Medium | Defrost, system check No Frost |
| Clicking and buzzing (cycle) | Malfunction of the starting relay | High | Replace the relay (you can do it yourself) |
| Vibration and rattling | Incorrect installation, touching furniture | Low | Align the legs, move them away from the wall |
This table covers the most typical scenarios, however, each model of equipment may have its own design features. For example, in two-compressor refrigerators, the sounds can be synchronized or, conversely, one compressor can cover the noise of the other.
When it is necessary to call a specialist
There are a number of situations when independent repair is not only impractical, but also dangerous. If, after carrying out basic diagnostics (defrosting, checking the installation, checking the internal shelves), the knocking does not stop, and the nature of the refrigerator’s operation has changed, it is better to contact a professional.
A particularly alarming signal is the combination of knocking with an increase in temperature in the chambers. If you hear that the compressor is overloaded (humming louder than usual, knocking), but there is no cold, this indicates serious problems in the refrigeration circuit: freon leakage, capillary system blockage or compression loss.
⚠️ Attention: Never try to open a sealed circuit yourself or replace the compressor without special equipment (vacuum pump, pressure gauge station). This can lead to injuries and final breakdown of the unit.
Also, the help of a specialist is needed if the knocking noise appears after a power surge in the network. In this case, the electronic control module could fail, which incorrectly sends signals to start the engine or fan, causing them to operate incorrectly and make noise.
☑️ Checklist before calling a technician
Noise prevention and extending service life
To minimize the risk of knocking and other extraneous sounds in the future, it is important to follow the operating rules. Regular defrosting (even for systems No Frost a preventive shutdown is recommended once a year) will help avoid ice buildup, which is a common cause of fan noise.
Keep the condenser (the grille at the back of the refrigerator) clean. Dust and pet hair accumulate on the tubes and impair heat transfer. The compressor is forced to work longer and harder to maintain the temperature, which accelerates its wear and can lead to vibrations and knocking.
- 🧹 Wipe the door seals regularly so that they do not tan and ensure a tight fit.
- 🧹 Do not put hot food in the refrigerator - this causes sudden steam formation and the load on the system.
- 🧹 Check the stability of the legs every six months, as they can unwind from vibration.
Timely maintenance and careful attention to the “well-being” of your refrigerator will avoid costly repairs. Remember that knocking is always a signal given by equipment, indicating that some process is not going according to plan.
The myth about quiet refrigerators
There is an opinion that modern refrigerators should operate absolutely silently. This is wrong. Even the most expensive models make sounds from the refrigerant and compressor. Complete silence is only possible when turned off.
Frequently asked questions (FAQ)
Why does the refrigerator knock only when turned on?
A knock when turned on is most often associated with the operation of the start relay or hydraulic shock in the compressor when the piston starts abruptly. If the knock is single and quiet, this is normal. If it is loud and repeated, the starter or motor mount is probably worn out.
Can an empty refrigerator knock?
Yes, an empty refrigerator can knock even louder than a full one. The products inside act as shock absorbers, dampening vibration of shelves and drawers. In addition, the compressor cools the empty chamber faster, but switching cycles may be more abrupt due to the lack of thermal inertia of the products.
Is it dangerous to operate the refrigerator if it starts knocking?
Short-term operation before the technician arrives is usually safe for the products if the temperature is maintained. However, prolonged operation of a knocking compressor can lead to its complete jamming or breakage of the tubes, which will make repairs economically unfeasible.
Why does an old refrigerator knock more than a new one?
Over time, the lubricant in the moving components of the compressor and fan dries out, the gaps increase, and the plastic becomes more fragile. This is a natural process of aging equipment, which leads to increased noise and vibration.