Why knocking is heard in the refrigerator: causes and solutions

An unexpected extraneous sound in the operation of household appliances always alarms the owner, especially if we are talking about a refrigerator that works around the clock. A characteristic knocking sound can occur suddenly, then fade away, then appear again with renewed vigor, which creates noticeable discomfort in the room. Often, users begin to panic, assuming that an expensive unit will soon fail, but noise does not always indicate a critical breakdown.

To understand the nature of the sound, you need to listen carefully to its rhythm and frequency of occurrence. Frequency of knocking often indicates the operating cycles of the compressor, while chaotic knocks can be caused by external factors or vibration of internal elements. In this article, we will analyze in detail the mechanics of the occurrence of noise and determine when you can handle it yourself, and when the intervention of a specialist is required.

It is important not to ignore the signals that your refrigeration unitgives, since timely diagnostics allows you to avoid expensive repairs. Different models, be it Indesit, LG or Bosch, have their own design features that affect the level of acoustic comfort. Let's figure out what exactly causes these sounds in your case.

Natural physical processes and operation of the compressor

The most common cause of knocking is the normal operation of compressorwhich is the heart of the refrigeration system. When the engine starts or stops, the piston inside the compressor experiences a sudden change in pressure, which may be accompanied by a dull thud. This phenomenon is absolutely normal for most modern models and does not require any intervention from the user.

In addition, gas expansion and compression processes are constantly occurring in the refrigerant circulation system, which also generates sounds. Thermal expansion plastic and metal parts of the case when the temperature changes causes characteristic crackling or clicking. This is especially often observed in new refrigerators or immediately after defrosting, when the temperature difference is greatest.

It is worth noting that modern inverter compressors operate much quieter than their old linear counterparts, but they are not completely silent. If the knocking sound occurs exactly when the light in the chamber is turned on or off (which signals that the thermostat is working), then most likely there is nothing to worry about. However, if the sound becomes ringing, metallic and repeats too often, it is worth paying attention to the condition of the fasteners.

⚠️ Attention: If a dull knock when starting the compressor is replaced by a hum, and then the unit abruptly goes silent and does not start again for several hours, this may indicate that the thermal protection relay has tripped. In such a situation, operating the device is dangerous.

Understanding physical processes helps to separate normality from pathology. The sounds of movement refrigerant through the tubes are often described as gurgling or flowing of liquid, which is also an operating parameter of the system. The main thing is that these sounds are not accompanied by vibration transmitted to the floor or walls.

Installation problems and vibration of the case

One ​​of the most commonplace, but often ignored causes of knocking is improper installation of the refrigerator. If the unit is not level, a misalignment occurs, which leads to uneven distribution of the load on the supports. As a result, the body begins to resonate, and the legs transmit vibration from the operating compressor to the floor, creating a drum effect.

To eliminate this problem, you need to check the horizontalness of the installation using a building level. Adjusting the height of the legs allows you to compensate for uneven floors and ensure a stable position of the body. It is also important to check the distance to the walls and furniture: if the refrigerator touches the back wall of the cabinet or side panel, vibration will be transmitted to them, causing rattling.

Often the source of noise is objects located inside the chambers or on the top panel. Cans, bottles or decorative items placed on top may vibrate and knock against each other due to the operation of the motor. Inside the chambers, poorly secured shelves or glass bottles standing close to the walls behave similarly.

Owners should remember that even a small gap between the refrigerator and surrounding objects is critical for normal ventilation and noise reduction. The lack of clearance leads not only to noise, but also to overheating of the condenser, which shortens the service life of the equipment.

Malfunctions of the No Frost system fan

In refrigerators with the system No Frost a special fan located in the freezer or refrigerator compartment is responsible for the circulation of cold air. Over time, ice can build up on the fan blades, especially if the door seal is broken or defrosting is infrequent. The ice crust creates an imbalance, and the blades begin to touch the walls of the casing, producing a rhythmic knocking or crackling sound.

Another cause of noise in this unit is wear of the fan motor bearings. In this case, the sound becomes more piercing and resembles a hum or howl, turning into a knock at certain speeds. If the fan is located in the freezer compartment, the sound may be less noticeable when the door is closed, but when opened it becomes clearly audible.

Diagnosis of this malfunction often requires partial disassembly of the interior panel. It is necessary to visually inspect the blades for chips and ice, and also check the free rotation of the shaft. A frozen fan is a common problem in winter or if the defrost sensor is faulty.

If ice is found, it must be carefully removed without using sharp objects, so as not to damage the evaporator. If the bearing wears out, the entire fan assembly will need to be replaced, since this part is usually not repairable. Ignoring the problem can lead to a break in the fan wiring or its complete jamming.

Wear of shock absorbers and compressor mounts

The compressor in the refrigerator is mounted on the frame using special shock absorbers or springs that dampen vibration when the engine is running. Over the years, rubber gaskets become tanned, cracked, or completely deteriorate, and metal springs can stretch or come off. As a result, the compressor housing begins to hit the metal frame or walls of the refrigerator body, creating a loud metallic clang.

You can determine this malfunction by carefully placing your hand on the body of the operating unit. If you feel a strong vibration radiating into your palm and hear rattling, the problem is most likely in the fasteners. Sometimes it is enough to simply tighten the mounting bolts, but more often it is necessary to replace rubber washers or pads.

In some models, the compressor is suspended on springs, and if one of them comes off, the engine will be distorted. This not only creates noise, but is also dangerous for the integrity of the copper tubes, which can burst from tension. In such a situation, operation of the device must be stopped immediately.

Timely replacement of shock-absorbing elements returns the refrigerator to quiet operation. Do not try to place wooden blocks or hard objects under the compressor - this will only increase the transmission of vibration. Use only specialized rubber parts or high-quality analogues.

Valve knocking and water hammer

A valve is installed in the refrigeration circuit that regulates the supply of refrigerant, and its operation may also be accompanied by sounds. Clicking sounds from the solenoid or bypass valve are normal and indicate that modes are switching correctly. However, if the clicking sounds become too loud and frequent, this may indicate power surges or a malfunction of the control electronics.

A more serious problem is water hammer, which occurs if liquid freon enters the compressor instead of gaseous freon. This can occur when the system is overcharging or the temperature regime is violated. Liquid, unlike gas, does not compress, and when the piston hits it, it makes a characteristic loud knock, which can lead to damage to the valve group.

What is the danger of water hammer?

Water hammer can lead to destruction of the compressor piston group, breakage of the connecting rod, or even piercing the motor housing. This is one of the most severe malfunctions, often requiring a complete replacement of the compressor.

It is difficult to diagnose a problem with the valves on your own, since special equipment is required to listen and measure the operating parameters of the system. If you hear sounds unusual for your refrigerator, similar to hammer blows inside the engine compartment, it is better to call a specialist.

It is important to consider that the quality of the refrigerant and oil also affects the operation of the valves. The use of low-quality materials during previous repairs may cause knocking to appear some time after servicing.

Diagnostics and methods for eliminating noise

Before taking active steps, it is necessary to conduct a thorough diagnosis. The first step should always be visual inspection and audition. Try pressing lightly with your hand on different parts of the housing, the compressor or the condenser grille. If the noise disappears when pressed, then you have found the source of vibration.

Next you should check the interior of the cameras. Remove all food, shelves and drawers, then turn on the refrigerator. If the knocking noise disappears, then the reason was the resonance of the objects. If the sound remains, the problem lies in the technical unit.

If external causes are eliminated, such as an uneven floor or touching walls, this is usually resolved quickly. However, if access to internal mechanisms is required, remember safety precautions. Any work inside the housing should only be carried out with the device disconnected from the mains.

⚠️ Attention: It is strictly forbidden to try to straighten the copper tubes of the refrigeration circuit while the compressor is running or under voltage. This can lead to depressurization of the system, leakage of freon and electric shock.

If simple methods do not help, and the knocking continues, you may need to replace worn parts. The table below shows the main actions depending on the type of problem identified.

When you need to call a technician

There are a number of situations when self-repair is not only ineffective, but also dangerous. If the knocking is accompanied by a burning smell, smoke or sparking, immediately unplug the refrigerator and call a specialist. You also need professional help if you discover a refrigerant leak or damage to the compressor oil circuit.

Complicated cases involving replacing a compressor, recharging the system or repairing electronics require special tools and qualifications. An attempt to eliminate such malfunctions with your own hands can lead to the final failure of the equipment and loss of warranty.

The technician will be able to accurately determine whether the knocking is a sign of impending failure of the compressor. Sometimes a knock is the last signal before the engine stops completely, and delay can leave you without a refrigerator at the most inopportune moment.

You should not save on diagnostics if you do not confident in their abilities. A professional eye often allows you to notice nuances that an inexperienced user will miss, which ultimately saves your money and food.

Preventing knocking and caring for equipment

In order for your refrigerator to work quietly and for a long time, it is important to follow the operating rules. Regularly check the cleanliness of the condenser grille at the back of the unit: dust and animal hair impair heat transfer, causing the compressor to work harder and creating unnecessary vibration. Cleaning with a vacuum cleaner or a soft brush once every six months significantly extends the life of the equipment.

Also make sure that the refrigerator is not overloaded with food. Overcrowded shelves and drawers can shift the center of gravity and create additional pressure on the walls, increasing resonance. Uniform distribution of products helps maintain balance inside the chambers.

Periodically check the condition of the door seals. If the rubber has lost its elasticity or is dirty, the door does not close tightly, which leads to frequent starts of the compressor and the formation of ice in the system No Frost. Wipe the seals with a soft cloth and, if necessary, treat with silicone grease.

Why does the refrigerator knock only at night?

At night, the overall noise level in the apartment decreases, and sounds that were invisible during the day against the background of household noise become clearly audible. In addition, at night the voltage in the electrical network may stabilize or, conversely, jump, which affects the operation of the compressor. Also at night, defrosting on a timer occurs more often, which is accompanied by characteristic clicks and noise of water.

Is it possible to lubricate a compressor if it is knocking?

Modern hermetic compressors are not designed to be lubricated by the user. They are filled with special oil, which circulates along with freon. Trying to add oil through a puncture or valve will upset the balance of the system and is guaranteed to lead to failure. You can lubricate only the external rubbing elements, if they are accessible, but not the motor itself.

Is knocking dangerous for food in the refrigerator?

The sound itself does not affect the quality of the food. However, if the knocking is caused by a malfunction leading to an unstable temperature regime (for example, the compressor does not reach the required speed or often turns off), then the temperature in the chambers may increase. This may lead to spoilage of perishable products. Therefore, it is important to eliminate the cause of the noise.

Does the age of the refrigerator affect the noise level?

Yes, with age, shock absorbers wear out, plastic dries out, and fasteners weaken. Older models of refrigerators, as a rule, are noisier than new analogues with inverter compressors. Natural wear of parts leads to increased gaps and vibrations that were not present when purchased.

Following these simple rules will help you avoid many problems. Remember that a refrigerator is a complex mechanism that requires attention and care. Regular maintenance and timely response to changes in its operation will ensure a long service life and silence in your home.