The appearance of extraneous sound in refrigerator, especially intrusive knocking, always causes anxiety for the owner of household appliances. Just yesterday the device worked almost silently, but today it makes sounds reminiscent of a hammer drill or knocking on a metal bucket. Such a change in the acoustic background is not just an irritating factor, but a signal that abnormal processes are occurring in the system. Ignoring these symptoms can lead to complete failure of the unit and spoilage of products. compressor that abnormal processes are occurring in the system. Ignoring these symptoms can lead to complete failure of the unit and spoilage of food.
Refrigeration equipment of modern brands, be it Indesit, Atlant or Bosch, is designed with minimal noise levels in mind. However, mechanical components wear out over time, and operating conditions are not always ideal. Knocking can occur both when the engine starts, and during its operation, as well as when stopping. Understanding the physics of the process will help determine whether an immediate call to a technician is required or whether the problem can be solved independently by simply changing the position of the case.
In this article we will analyze in detail the mechanical and electrical causes of knocking. We will look at the device piston compressor, the effect of vibration on pipelines and the role of starting equipment. It is important to distinguish normal operating noise from a critical malfunction that requires complex repairs. Careful diagnostics at an early stage can often save significant money.
Mechanical causes: vibration and contact of tubes
The most common and least dangerous cause of knocking is physical contact of the copper tubes of the refrigeration circuit with each other or with the walls of the housing. During operation piston compressor reciprocating movements occur, which are transmitted to the entire system. If the device is not level or was moved during cleaning, the gaps between the elements could decrease to critical values. In this case, each vibration turns into a distinct metallic clang.
Often the source of sound becomes capillary tubewhich is adjacent to the housing of the motor-compressor. When the engine starts, the vibration amplitude is maximum, and the copper hits the steel. This creates a characteristic ringing or knocking noise that can last a few seconds or continue throughout operation. It is also worth checking that the tubes are not touching the rear radiator grille or the interior walls of the cabinet. Even a slight displacement of 1-2 millimeters can generate a loud sound.
⚠️ Attention: Before unbending the tubes with your hands, make sure that the refrigerator is unplugged and that you have dried your hands. Copper is a soft metal, and careless movement can damage the seal of the circuit, which will lead to refrigerant leakage.
Sophisticated equipment is not required to fix this problem. It is enough to carefully move the vibrating elements away from each other, increasing the gap. If the tubes touch the body, you can place a small piece of rubber or thick cardboard between them. It is important not to overdo it and not to bend the tubes at an acute angle, as this will disrupt the circulation of freon.
Sometimes knocking occurs due to the fact that the compressor itself is poorly secured to the frame or vibration supports. Rubber washers that dampen vibrations dry out or tear over time. As a result, the metal engine casing begins to bang against the metal base frame. Check the mounting bolts and the condition of the rubber shock absorbers. Replacing them is a simple procedure that often returns silence.
There is another nuance associated with installing a refrigerator. If the floor is uneven and the machine's feet are not adjusted, the cabinet may warp. This creates internal stress in the structure, which increases vibration. Adjusting the height of the legs using a building level helps to evenly distribute the weight and reduce resonance.
Problems of the starting relay and electrical part
If no mechanical contacts are detected, and a knock is heard exactly when the refrigerator is turned on, there is a high probability of a malfunction. starting relay. This small unit is responsible for starting the compressor motor. Inside it there is a coil and a movable core (striker), which, under the influence of an electromagnetic field, must close the contacts. If the mechanism is worn out or dirty, the core may rattle without performing its function, or make a loud click with each unsuccessful start attempt.
A characteristic metallic clang or crackling sound in the first seconds of operation often indicates that the starting winding is not turned off in time. This happens when the relay contacts “stick” or, conversely, cannot close. The engine hums, tries to start, there is a knock, and the thermal protection is triggered. After some time, the cycle repeats. This situation is dangerous for the electric motor windings, as they can overheat and burn out.
Modern models of refrigerators, such as Samsung or LGcan use electronic starting devices that are quieter than mechanical ones. However, they are also prone to breakdowns. If you hear a series of rapid clicks before starting or during operation, this is a sure sign that the relay is dying. Replacing this component is one of the most frequent and inexpensive procedures in the repair of refrigeration equipment.
In addition to the relay, it is worth paying attention to the condition of the wiring and contacts. A loose connection can cause sparking, which is accompanied by a sound similar to a crackling or dry knock. This is especially true for older refrigerators, where the wire insulation may have cracked over time. Checking the electrical circuit requires caution and the presence of a multimeter.
How to check the start relay yourself?
Remove the relay from the compressor (after turning off the refrigerator). Shake it near your ear. If a clear knocking or rattling sound is heard inside, as if a part is loose there, then the mechanical part is damaged and the relay must be replaced. Also inspect the contacts for carbon deposits.
Wear of the compressor piston group
The most serious cause of knocking is wear of the internal components of the compressor itself compressor. Inside the sealed casing there is a complex mechanism that converts the rotation of the shaft into the movement of the pistons. Over time, the rubbing parts wear out and gaps appear, which lead to metal hitting metal. If the knocking is dull, deep and comes directly from the “belly” of the engine, this often indicates wear of the crankshaft or piston group liners.
In the initial stage of wear, knocking can only appear at startup, when the oil has not yet been distributed over all components, and the pressure in the system has not been equalized. As the oil warms up and thins, the sound may subside. However, the progression of this process inevitably leads to jamming of the compressor. At this moment, the engine will either stop starting or the winding will burn out.
Sometimes the cause of knocking is the destruction of the internal engine mount. The motor inside the casing is mounted on springs to dampen vibrations. If one of the springs breaks, the engine begins to dangle and hit the walls of the casing during operation. This creates a very loud, sharp metallic knocking noise that can't be ignored. Repair in this case is usually impractical; a complete replacement of the unit is required.
It is worth noting that different types of compressors make different noise. Inverter models, which can be found in refrigerators Haier or Liebherr, work differently than classic ones. They do not make loud clicking noises when starting, as they start smoothly. If the inverter refrigerator begins to knock, this is almost always a sign of a critical electronic or mechanical malfunction that requires professional diagnostics.
It is difficult to diagnose wear of the piston group without opening the casing, but it is possible indirectly. If the refrigerator has stopped freezing, but the compressor is knocking and heating up quickly, the likelihood of mechanical destruction inside is very high. In this case, further operation is impossible.
The influence of refrigerant and water hammer
A sound reminiscent of bubbling water or rolling balls is often confused with knocking, but its nature is different. This circulates refrigerant (freon) throughout the system. However, if there is excess air or moisture in the system, the sound may become harsher and more percussive. Moisture, freezing in narrow places of the capillary tube, forms ice plugs, which are then torn off by a gas flow, creating characteristic shocks.
Hydraulic hammer is a rarer, but dangerous phenomenon. It can occur if liquid refrigerant enters the compressor along with freon vapor. The fluid is incompressible, and its entry into the piston cylinder causes a powerful shock that can break the valves or connecting rod. This is usually accompanied by a loud bang and subsequent stopping of the engine. The reasons may lie in a malfunction of the thermostat, which does not turn off the compressor in time, or in a freon leak that upsets the pressure balance.
If you hear a dull knock or gurgling sound after the compressor stops, this may be due to pressure equalization in the system. Normally, this process is relatively quiet. Loud sounds indicate that the gas is passing through obstacles or throttling devices with high speed and turbulence.
Impaired amount of refrigerant in the system also affects the acoustics. If there is a lack of freon, the compressor works with increased load, trying to increase temperature, which can increase vibration and noise. If there is excess (for example, after unqualified repairs), the pressure in the system increases, and the valves can work with overload, making clicking sounds.
Diagnostics: how to determine the source of the sound
To accurately determine why the engine is knocking, it is necessary to carry out consistent diagnostics. The first step is to localize the source. Place your hand (carefully so as not to get burned or receive an electric shock) to different parts of the body of the operating refrigerator. The vibration will tell you exactly where the impulse originates. If the entire back wall hums and knocks, the problem is most likely in the compressor mount or the contact of the tubes.
It is important to distinguish between the sounds made by the motor itself and the sounds coming from inside the chamber. Sometimes the cracking of ice in the freezer or the noise of the fan (in systems No Frost) is mistaken for the knock of the motor. The fan may be hitting ice or have broken bearings, which creates a rattling sound, very similar to mechanical knocking.
Try tilting the refrigerator back slightly (being careful). If the knocking stops or changes in tone, it means that the tubes are touching or the device is in an unstable position. If the nature of the sound does not change when changing the position of the housing, the problem lies deeper - inside the compressor or in its electrical part.
Listen to the moment it turns on. It is in the first 3-5 seconds that problems with the starting relay and water hammer appear. If a knock is heard only at this moment and then the engine runs smoothly, the focus of attention should be shifted to the starting equipment. Constant knocking during operation is a sign of mechanical wear.
Comparative table of malfunctions
For the convenience of systematizing the causes and symptoms, we have compiled a table that will help you quickly navigate the nature of the malfunction. Pay attention to the combination of sound and accompanying signs.
| Sound type | Probable cause | When it occurs | Danger |
|---|---|---|---|
| Metal ringing/clanging | Touching of tubes, loose fasteners | During operation and vibration | Low (risk of tube chafing) |
| Loud clicking and buzzing | Starter malfunction relay | At the moment of start-up | High (risk of engine combustion) |
| Thud knocking inside the motor | Wear of the piston group | Constantly or when start | Critical (the compressor needs to be replaced) |
| Gurgling, overflow | Freon circulation, moisture | During operation and after stopping | Average (risk of ice jam) |
Is it possible to eliminate the knocking yourself
The answer to this question depends on the identified cause. If the problem is touching the pipes or improper installation, any home handyman can repair it. It is enough to move the tubes, add insulation or level the legs of the refrigerator. Replacing the start relay also falls into the category of simplest operations: you need to remove the old unit, remember the connection diagram (or take a photograph) and install a new one, similar in markings.
However, if diagnostics indicate problems inside the sealed compressor casing or a freon leak, independent repair is impossible without special equipment. To replace the compressor, you need a vacuum pump, a pressure gauge station, a torch for soldering copper pipes and a supply of refrigerant. In addition, the system must be thoroughly dried to prevent moisture from entering.
⚠️ Attention: Opening the compressor casing at home is strictly prohibited. This breaks the seal and requires complex soldering and fine tuning. The cost of such “repairs” often exceeds the price of a new compressor, and reliability tends to zero.
If you are not confident in your abilities, it is better to turn to professionals. Service center technicians have access to original spare parts and can provide a guarantee on the work performed. An attempt to repair a complex unit without experience can lead to final breakdown of the equipment.
Preventing noise and extending service life
In order for the refrigerator motor to work quietly and for a long time, it is important to provide it with the correct operating conditions. Do not install the refrigerator close to a wall or furniture. A gap of 5-10 cm is necessary for free air circulation and reduced resonance. Regularly check the cleanliness of the condenser grille at the back: dust and animal hair worsen heat transfer, causing the motor to work harder and noisier.
Monitor the room temperature. If the refrigerator is located in the kitchen, where it is very hot in summer, the load on the compressor increases many times over. This leads to rapid wear of the oil and mechanical parts. Also, do not overload the refrigerator with food immediately after defrosting - a sharp jump in temperature will force the motor to work at its limit, which can cause water hammer.
Regular defrosting (for drip systems) prevents the formation of a thick ice crust, which can interfere with the operation of the evaporator and create additional noise during defrosting. For systems No Frost it is important to monitor the serviceability of the drainage system so that water does not freeze in unintended places.
☑️ Check before calling a technician
Often asked questions (FAQ)
Is it normal if the refrigerator knocks immediately after switching on?
Short-term noise or buzzing in the first seconds is acceptable, since the motor starts under load. However, a loud metallic knock or a series of clicks after which the refrigerator turns off indicates a malfunction of the start relay or compressor.
Can a new refrigerator knock?
A new device can make sounds if it is not installed correctly (shipping bolts are not unscrewed, although refrigerators usually do not have them, unlike washing machines, but they can be shelf clamps) or stands on an uneven floor. Also, in new models, the operation of the refrigerant may be heard. If the knocking is strong, this may be a defect.
How much does it cost to replace a compressor?
The cost consists of the price of the unit itself (which can be high) and the cost of soldering, vacuuming and refilling with freon. It is often more economically feasible to consider purchasing a new refrigerator if the old one has served for more than 10 years.
Why does the refrigerator knock, but freeze?
This indicates that the compressor is still functioning, but mechanical wear has already begun. Most likely the bearings or bearings are worn out. It will work, but not for long. It is recommended to prepare a replacement, since a breakdown can happen at any time.