The sudden appearance of extraneous sounds in the operation of household appliances always causes alarm, especially if we are talking about a refrigerator that works around the clock. Knock in the refrigerator can vary from a barely noticeable clicking sound to loud knocks, reminiscent of the operation of a jackhammer. Owners often panic, believing that the unit is about to fail, but noise does not always indicate a critical breakdown. Sometimes this is just a design feature or a consequence of improper installation.
Understanding the nature of sounds is the first step to solving the problem. Mechanical noise, vibration and hydraulic shock have different tonality and frequency. Modern models Inverter compressors operate much quieter, but even they are not immune to mechanical problems. In this article, we will look in detail at why such sounds may occur, how to distinguish normal operation from a malfunction, and in what cases a call to a technician is required.
Ignoring loud knocks can lead to more serious consequences, including destruction of the internal components of the compressor or a violation of the tightness of the system. If the knocking is accompanied by a cessation of cooling or the appearance of puddles under the equipment, it is dangerous to operate the device. Correct and timely diagnostics will help save significant amounts of money on expensive repairs or purchase of new equipment. Let's look at the main causes of noise.
Normal operation of the compressor and refrigerant
Before sounding the alarm, you need to make sure that the sounds you hear are not standard for your model equipment. Compressor operating cycle often accompanied by characteristic clicks when turning the engine on and off. This triggers the starting relay, which provides an impulse to start the engine. In older models, this sound can be quite loud and harsh, which sometimes frightens users, but in fact this is a normal physical process.
In addition to electrical clicks, boiling and condensation processes constantly occur in the refrigerant circulation system. Liquid freon, passing through the capillary tube and evaporator, makes gurgling, iridescent sounds or a quiet hiss. Inverter compressors they can hum or emit a low-frequency hum, which changes depending on the load. If the refrigerator has just been defrosted or loaded with warm food, the intensity of the system increases and the sounds become more distinct.
⚠️ Attention: If a quiet, uniform hum suddenly gives way to a loud clang, metal grinding or frequent knocks, this is a signal of a malfunction. Normal operating noise should not cause physical discomfort or interfere with sleep in the next room.
Thermal expansion of materials should also be taken into account. The plastic of the inner housing and the metal elements of the tubes may become slightly deformed when the temperature changes, producing a characteristic crackling sound or single clicks. This is especially noticeable immediately after turning on the fast freezing mode or after defrosting. Typically, such sounds do not pose a threat and go away on their own after some time.
Installation problems and vibration of the case
One of the most common reasons why the refrigerator is knocking or buzzing is its incorrect location. If the unit is not level, vibrations from the operating compressor are transmitted to the floor and amplified by resonance. Even a slight misalignment can cause the case to come into contact with the walls of a niche, kitchen furniture or internal elements, creating a rattling sound.
To check the stability, you need to rock the refrigerator from side to side. It must stand firmly on all four support legs. Height adjustment is usually done by twisting or twisting the front legs. Floating floors or soft floor coverings (carpet, linoleum with a soft backing) can also increase vibration, creating the illusion of equipment failure.
Often the source of knocking is objects located in the immediate vicinity or inside the chamber. Bottles placed close to each other on a shelf may hit the glass due to vibration. Heavy pots placed on the door can also create noise when they slam shut or when the motor is running. Check whether the pipes of the heating system or water supply system are touching the back wall of the appliance.
Faults in the compressor and start relay
If external factors are excluded, you should pay attention to the heart of the refrigerator - the compressor. Hydraulic hammer Inside the compressor is one of the common causes of a loud knocking sound when starting up. This occurs when liquid refrigerant or oil enters the cylinder instead of the gaseous phase. The piston, trying to compress an incompressible fluid, emits a sharp blow. Frequent water hammer can quickly damage the motor.
Another reason is wear or breakdown starting relay. This small element is responsible for starting the engine. If the relay contacts are burnt or the mechanism is jammed, when you try to start, you will hear a loud click, followed by a buzzing sound, and then a second shutdown click. The motor may try to start several times before it goes into protection, which is accompanied by a series of knocks.
Is it possible to replace the starting relay yourself?
Replacing the starting relay is one of the few operations available to beginners. The relay is simply removed from the compressor contacts (usually it is held on by a bracket or latches). However, it is important to buy exactly the same relay model, since they differ in operating current and design. An error in selection can lead to combustion of the compressor windings.
Wear of the bearings or liners of the compressor crankshaft leads to metallic knocking and rumble during operation. Unlike the one-time knock at start-up, this sound continues as long as the engine is running. Over time, it intensifies, and cooling efficiency decreases. Repairing such a compressor is often not economically feasible; it is easier to replace the entire unit.
Unbalancing of fans in the No Frost system
In refrigerators with the system No Frost fans are responsible for circulating cold air. Over time, ice may build up on the blades, or a foreign object (a piece of packaging, a label) may get into them. This leads to an imbalance of the impeller, and it begins to touch the walls of the housing or ice, producing a rhythmic knocking or crackling sound.
Often the problem lies in the evaporation fan located behind the back wall of the freezer. If the defrost system is not working properly, ice may accumulate unevenly and block the path of the blades. In some models, noise may be produced by the condenser fan located in the lower part of the unit (near the compressor), where dust or small debris could have gotten in.
Fan motor bearings also tend to wear out. At first, this manifests itself as a quiet hum, which turns into rattling and knocking. If when you stop the fan by hand (carefully!) the noise disappears, then the problem is in this unit. Replacing a fan usually does not require complex tools and takes little time.
Foreign objects and products as a source of noise
Do not underestimate the influence of the contents of the refrigerator on acoustic comfort. Glass shelves, if they do not have rubber seals or are loose, may ring when the case vibrates. Heavy objects on door shelves when opened or slammed can create a shock sound, which users mistakenly mistake for knocking inside the unit.
Ice build-up in the freezer is another common “musician”. When the defrost system is running or simply due to vibration, large pieces of ice can break off and fall onto the shelf or food, creating a loud knocking sound. Ice can also jam the mechanisms of the air supply dampers, which is why the damper motor hums or crackles, trying to turn the frozen mechanism.
| Sound type | Probable cause | Localization | Urgency of repair |
|---|---|---|---|
| Single loud click | Start relay / Thermostat | Rear, below or inside | Low (if the refrigerator is working) |
| Metal clanging | Compressor wear | Lower part at the back | High |
| Rhythmic crackling | Fan / Ice | Freezer compartment | Average |
| Gurgling / Overflow | Freon movement | Throughout the entire body | Normal operation |
Diagnostics and elimination methods noise
To accurately determine the cause of the knocking, it is necessary to carry out consistent diagnostics. Start with a visual inspection and stability check. Make sure that the refrigerator does not touch walls or furniture. Then listen to where exactly the sound is coming from: from below, behind or from inside the cameras. This will help localize the faulty unit.
If suspicion falls on the fan, partial disassembly will be required. To check the compressor, sometimes it is enough to remove the rear metal cover (crankcase) at the bottom of the refrigerator. Be careful: compressor the surrounding tubes may be hot and some parts may be live. Before any work inside the appliance, be sure to disconnect it from the power supply.
☑️ Action plan for noise
If a mechanical failure is detected, such as destruction of the compressor suspension (shock absorbers on which it is attached to the frame), you can try replacing the rubber washers or bushings. Often the compressor itself is intact, but due to a broken suspension it hits the metal housing every time it starts. This is a common reason why Atlant refrigerator or Indesit starts to knock heavily after several years of operation.
⚠️ Attention: It is strictly forbidden to open the sealed compressor casing (cutting off the welded cap) at home. This requires special equipment for vacuuming and charging with freon. An attempt to independently repair the “internals” of the motor is almost guaranteed to lead to final failure.
When you need to call a specialist
There are a number of symptoms in which self-repair is not only ineffective, but also dangerous. If the refrigerator is knocking at the same time it stops freezing, or there is no cold on the walls of the chambers, the problem most likely lies in a freon leak or a blockage of the capillary system. A knocking sound in this case may be a sign of the compressor running dry or water hammer due to circulation problems.
Replacing a compressor is a complex technological process that requires a vacuum pump, a pressure gauge station, a burner and a supply of refrigerant. In addition, modern refrigerants (for example, R600a) are explosive when exposed to air in a certain concentration. Therefore, such work should only be performed by certified specialists.
Also, professional help is needed if the problem is in the electronic control module, which incorrectly sends signals to start and stop the engine, causing frequent clicks and knocks of the relay. Board diagnostics require special knowledge and equipment. Do not attempt to repair electronics without the appropriate qualifications, as this may result in a short circuit.
Prevention of noisy operation of the refrigerator
In order for your refrigerator to operate quietly and for a long time, it is important to follow the operating rules. Regular defrosting (for drip systems and older models) will prevent excessive ice accumulation, which can cause fans to knock or heat exchange problems. Even in No Frost systems, it is recommended to carry out a complete defrosting and washing once a year.
Keep the condenser grill at the back of the refrigerator clean. Dust and animal hair clogging the radiator cause the compressor to work harder and overheat, which shortens its life and can increase noise. The back of the unit should be vacuumed every 6-12 months.
Proper loading of the chambers also plays a role. Do not place hot foods, do not overload shelves, and ensure that food does not touch the back wall where the evaporator is located. Following these simple rules will help avoid unnecessary noise and extend the life of your kitchen assistant.
How to extend the life of a compressor?
Ensure good air flow to the back wall of the refrigerator. Do not move the equipment close to the wall, leave a gap of at least 10-15 cm. Overheating is the main enemy of the compressor, leading to thickening of the oil and increased wear of rubbing parts.
Why does the refrigerator make a knock only when starting up?
A single knock or a series of clicks at the moment of switching on is usually associated with the operation of the starter relay or solenoid valve. If there is only one knock and the refrigerator starts to freeze normally, this is normal. If the series of clicks is repeated endlessly and there is no cold, the relay cannot start the compressor and it needs to be replaced.
Is it dangerous to continue using the refrigerator if it is knocking?
If the knocking is caused by vibration or objects, it is not dangerous, but noisy. If the compressor knocks (metallic clanging), prolonged operation will lead to its complete destruction. In the worst case, the tubes may rupture and freon may leak. It is better to carry out diagnostics.
Can a new refrigerator knock?
Yes, in the first days of operation, a new refrigerator can make various sounds: cracking plastic, the noise of flowing liquid, clicks. This is a period of breaking-in of parts and stabilization of temperatures. If after 3-5 days the loud knock does not disappear, it is worth checking the installation for horizontalness.
How to distinguish the knock of a compressor from the noise of a fan?
The knock of a compressor is normal, dull and coincides with the vibration of the housing. The fan noise is higher frequency, similar to crackling, rustling or rhythmic beating. To check the fan in the No Frost system, you can temporarily turn it off (open the circuit) and listen to see if the sound disappears.
What to do if the refrigerator hums and knocks after defrosting?
After defrosting, water may remain in the system, which, when frozen in the drainage or on the fan blades, causes noise. Let the refrigerator operate normally for a few hours. If the knocking does not go away, check to see if a piece of ice has gotten into the fan or if the water in the tray above the compressor has frozen.