Extraneous sounds emitted by household appliances are often the first signal that a malfunction has occurred in the system. If your the refrigerator is knockingemits loud clicking or humming noises, this cannot be ignored, since acoustic discomfort often hides serious mechanical faults. In contrast to the quiet, uniform hum of a running motor, knocking indicates vibration of parts, impacts of the compressor on the housing, or problems with refrigerant circulation.
Before calling a technician, it is important to conduct an initial diagnosis to understand the nature of the noise. Often the reason lies in a banal misalignment of the case or the tubes touching each other, which you can fix yourself in a few minutes. However, if compressor makes metallic clanging sounds or a plastic crack is heard, deeper intervention in the unit will be required.
In this article we will analyze in detail all the possible causes of knocking, from simple installation errors to complex breakdowns of internal components. You will learn how to distinguish normal operating noise from an alarm and what actions need to be taken to restore silence in the kitchen.
Is normal operating noise or a sign of a breakdown?
Modern models of refrigeration equipment, especially with the system No Frostcannot operate absolutely silently. Freon circulation, relay switching on and off, fan operation - all these processes are accompanied by a certain acoustic background. It is important to learn to distinguish between normal sounds and those that indicate a malfunction. A quiet gurgling of liquid in the tubes, periodic soft humming of the motor and rare clicks of the thermostat are considered normal.
The alarm should be sounded if the character of the sound changes to a metallic clang, a loud knock or a piercing whistle. Users often confuse defrosting sounds with a breakdown. For example, when defrosting, ice may crack, fall onto the evaporator, or flow into the drain pan with a characteristic noise. If the refrigerator is knocking rhythmic and loud, especially when starting the engine, this is a clear sign of a mechanical problem.
⚠️ Attention: If the knocking is accompanied by a lack of cold in the chambers or excessive heating of the side walls, operation of the appliance should be stopped immediately. avoiding complete failure of the compressor.
For an accurate diagnosis, listen to where exactly the sound comes from: from below, from behind or from inside the chambers. Localizing the source will help narrow down the possible causes. Below is a table to help classify sounds and their likely sources.
| Sound Type | Probable Cause | Danger Level |
|---|---|---|
| Rhythmic metallic knocking | Compressor malfunction or valve | High |
| Crackling of ice or plastic | Thermal expansion/contraction of materials | Low |
| Humming with vibration | Tubes touching the body or floor | Medium |
| Whistling or hissing | Freon leak or problem with the fan | High |
Installation and external problems factors
One of the most common reasons why the refrigerator is knocking or vibrates is incorrect installation. If the unit is not level, the running compressor causes a resonance of the housing, which is transmitted to the floor and walls. Vibration increases if the refrigerator's feet are not adjusted or if it is placed too close to furniture. Quite often, the cooling system pipes located at the rear can touch the wall or each other, creating a rattling sound every time the engine starts.
Check the distance between the back wall of the appliance and the wall of the room. It should be at least 5-7 centimeters for free air circulation. If the refrigerator is moved close, the vibration of the compressor will be transmitted to the building structures, creating the effect of increased knocking throughout the apartment. It is also worth inspecting the space around the equipment: sometimes foreign objects that fall behind the unit fall into the vibration zone.
Make sure the floor is under The refrigerator is smooth and solid. On soft surfaces, such as linoleum with a thick base or carpet, equipment can “walk”. Use a building level to check for levelness. Adjusting the height of the legs is a simple procedure that often eliminates noise without calling a technician.
Faults in the compressor and start relay
The heart of the refrigerator - this is a compressor. If this is the one making the loud knocking noises, the problem could be serious. The internal suspension of the motor-compressor is made on springs that dampen vibration. Over time, the metal of the springs can become tired, burst or shift, and then when the piston group operates, metal will hit metal. This sounds like a loud, distinct knocking noise, especially when starting or stopping the engine.
Another common cause is a faulty start relay. This small element is responsible for starting the motor windings. If the relay contacts are burnt or the mechanism is stuck, the compressor may try to start, make a sharp click or knock, and turn off. In such cases, the motor may hum for several seconds and then suddenly stop, after which the cycle is repeated after a certain time.
Diagnostics of the compressor requires caution. If you hear that the refrigerator is knocking it is in the area of the motor (usually the lower rear part), try to gently press the tubes or the compressor housing itself with your hand (only if it is not hot!). If the noise changes or disappears, the vibration is transmitted to neighboring elements. However, if the knocking comes from inside the compressor “pot”, this is a sign of internal mechanical failure.
⚠️ Attention: Replacing or repairing the compressor yourself requires special equipment for vacuuming the system and charging with freon. Without skills and tools, it is better not to open a sealed circuit.
In some cases, knocking can be caused by a pressure control valve if it is built into the motor design. This is typical for inverter models, where the mechanics work differently than in classic linear compressors. Inverter engines are usually quieter, but if their electronic control boards break down, high-frequency squeaks or crackles may occur.
Is it possible to change the compressor yourself?
Replacing a compressor at home is only possible in theory, but in practice requires soldering copper tubes, using nitrogen for purging, a vacuum pump and scales for accurate refueling refrigerant. Violation of the technology will lead to rapid breakdown of the new motor.
Fan and No Frost system
In refrigerators with a system No Frost fans are responsible for circulating cold air. Over time, ice can build up on the blades, or moisture and dirt can get into the fan motor bearing. As a result, the fan begins to hum, crackle, or knock on ice. The sound often resembles a propeller hitting a foreign object.
If a knocking sound is heard inside the freezer or refrigerator, most likely the problem is with the fan. In some models, access to it is blocked by a plastic panel. If the blades are frozen to the wall or body, a rhythmic knocking sound will be heard when rotating. Also, a worn fan bearing emits a characteristic growing hum that turns into a squeal.
To eliminate the problem, defrosting is often required. If the refrigerator is left turned off for 24 hours, the ice will melt and the fan may start running quietly again. If, after defrosting, the noise returns after a few days, it means that the tightness of the door seals is broken or the defrosting heating element is faulty, and moisture constantly gets into the fan operating area.
☑️ Fan diagnostics
Deformation and displacement of the tubes
Copper and aluminum tubes through which the refrigerant circulates are located along the entire perimeter of the refrigerator. During transportation or careless cleaning, they may shift and begin to touch each other or the walls of the case. When the compressor operates, pulsating vibrations pass through the tubes, and if there is a point of contact, a loud metallic knock or rattle occurs.
To fix this problem, you need to gain access to the rear of the unit. Visually inspect the location of the tubes. If you see that two tubes are touching, you need to carefully separate them with your hands (being careful not to damage the thin metal) and fix them at a distance of 1-2 cm from each other. Sometimes installing rubber gaskets or clamps at the mounting points helps.
It is also important to check the fastening of the compressor itself to the frame. The bolts can become loose due to constant vibration, and then the entire motor will bang against the metal base. Tightening the mounting bolts often solves the problem of loud clanging.
⚠️ Attention: Use extreme caution when aligning the tubes. Damage to the tube will lead to an immediate release of freon and will require expensive repairs with soldering and refilling.
Ice plugs and blockages in the system
Sometimes knocking in the refrigerator is caused not by mechanical parts, but by the physics of processes inside the cooling system. The so-called "water hammer" or noise when freon passes through narrowed areas can sound like gurgling or periodic blows. This often happens when the capillary tube or filter drier is clogged.
If an ice plug has formed in the system (for example, due to moisture in the circuit), the refrigerant flow is disrupted. The compressor works with increased load, trying to push gas, which causes a change in the operating sound. In such cases, the refrigerator can work cyclically: make noise, then die down, then make noise again.
It is difficult to diagnose a blockage without pressure gauges, but an indirect sign is insufficient cooling of the chambers when the motor is running. If the refrigerator is knocking it does not freeze well, most likely the problem lies in the circulation of the refrigerant.
When you need to call a technician
There are a number of situations when self-repair is not only ineffective, but also dangerous. If you have checked the installation, made sure that the tubes are not touching and defrosted, but the knocking does not stop, there is likely a problem within the unit. Replacing the compressor, repairing the defrost system or removing blockages requires a professional approach.
A specialist is needed if:
- 🔨 The knock comes directly from the compressor housing (internal knocking of valves or pistons).
- 🔥 The compressor gets very hot and immediately turns off.
- ❄️ The refrigerator has stopped freezing or the temperature in the chambers is unstable.
- 💧 A puddle of oil or water has appeared at the bottom of the case.
Professional diagnostics will allow you to accurately determine the unit that requires replacement and avoid unnecessary purchase costs unnecessary details. Remember that timely repairs are often cheaper than replacing the entire refrigerator.
Why does the refrigerator make sounds only at night?
At night, the overall noise level in the room decreases, and the sounds of operating equipment become more noticeable. In addition, the power supply often drops at night, which can make it difficult for the compressor to start, causing louder relay clicks or humming noises. Also, at night, automatic defrosting programs may turn on, which go unnoticed during the day.
Can a new refrigerator knock?
Yes, a new refrigerator can make sounds during the “break-in” period. The lubricant in the compressor is distributed unevenly, the parts are rubbing in. Usually after 2-3 days of operation the noise subsides. If the knocking is strong and does not go away after a week, this is a reason to contact a service center under warranty.
Is knocking dangerous for the products inside?
The sound itself does not affect the products. However, if the knocking noise is caused by a compressor malfunction or loss of seal, the temperature in the chambers may begin to rise. In this case, the products may spoil. Monitor the temperature with a thermometer.
How to extend the life of a compressor?
For a longevity compressor, it is important to provide good ventilation at the back, not to put hot foods inside, defrost regularly (if there is no No Frost) and protect equipment from power surges using a stabilizer or surge protector.