A sudden knocking sound in the refrigerator can turn a quiet kitchen into a source of constant irritation. This sound often signals that a complex mechanism has experienced a malfunction that requires immediate attention. Ignoring extraneous sounds can lead to serious damage to expensive equipment and damage to products.
In most cases, extraneous noise is not a harbinger of disaster, but indicates a specific malfunction that can be eliminated. Understanding the nature of the sound allows the owner to quickly classify the problem: whether it is a mechanical failure, a water hammer, or simply vibration of the housing. Correct diagnosis at an early stage saves significant money on calling a technician.
In this article we will analyze in detail the physical causes of knocking in various units of the unit. You will learn how to distinguish a normal operating sound from a dangerous signal and what actions need to be taken to restore silence.
Main sources of mechanical knocking
The most common cause of sharp, jerky sounds is the operation compressorwhich functions as the heart of the refrigeration system. If the unit is old or installed unevenly, vibrations from the running motor are transmitted to the housing and surrounding objects. In this case, the knocking is rhythmic in nature and coincides with the cycles of turning the engine on and off.
Often the source of the sound is not the motor itself, but its mounting elements. Loose bolts or worn rubber shock absorbers stop dampening vibrations, turning the body into a resonator. In models with an inverter compressor the nature of the noise may differ from classic linear models, but the diagnostic principles remain similar.
Another source of mechanical sounds can be the condenser tubes located on the rear wall. When the metal thermally expands during operation, they may come into contact with each other or with the cabinet wall, producing a characteristic ringing or knocking sound. To fix this problem, it is often enough to simply carefully straighten the tubes to increase the gap between them.
⚠️ Attention: Before touching the rear grille or compressor, be sure to unplug the refrigerator from the electrical outlet. Heating elements and electrical contacts may be live or hot.
Problems with the fan in No Frost systems
Refrigerators equipped with a system No Frost or Full No Frosthave built-in fans to circulate cold air. Over time, the rotating blades can hit frozen ice or foreign objects, causing a loud cracking or knocking noise. This sound is usually located at the top of the freezer or behind the rear panel of the refrigerator compartment.
The noise is often caused by a worn fan bearing. At the beginning of operation, the defect manifests itself as a quiet hum, which gradually turns into a loud knock. If you do not replace the fan in time, the motor may burn out, which will lead to defrosting of food and failure of the entire cooling system.
It is also worth checking whether pieces of food or packaging material have gotten into the rotation zone of the blades. Sometimes when loading food, light foil or the edge of the bag may be accidentally pulled into the air intake by the air flow. Removing the foreign object completely solves the noise problem.
☑️ Fan diagnostics
It is important to consider that in some models the fan only works when the doors are open or, conversely, only when the doors are closed. The nature of the sound changes depending on the position of the door, which helps to accurately identify the source of the problem.
The influence of ice and defrosting on the operation of the unit
The accumulation of ice in the evaporator is a classic situation that leads to knocking. When the layer of ice becomes too thick, it begins to interfere with the operation of the fan or damper that distributes cold air. When you try to turn the damper, the motor makes a characteristic cracking sound, signaling a mechanical obstacle.
In addition, pieces of ice can break off and fall onto metal shelves or glass surfaces, creating loud sounds that frighten owners. This often happens during the automatic defrost cycle, when the heating element melts the ice and large pieces lose adhesion to the surface.
If the refrigerator has not defrosted for a long time, the efficiency of heat transfer decreases, and the compressor is forced to work with increased load. This leads to overheating and accelerated wear of parts, which can also be accompanied by a change in the acoustic profile of the device.
How to quickly defrost a refrigerator without risk?
For accelerated defrosting, you can use hot water containers placed on shelves. Do not use a hair dryer or other heating devices, as a sudden temperature change can damage the plastic and evaporator tubes.
Vibration of the housing and improper installation
One of the most commonplace, but common causes of knocking is the incorrect installation of the refrigerator on the floor. If the feet are not level, the housing may wobble or vibrate when the compressor operates. This vibration is transmitted to the floor, walls and nearby objects, creating a humming or rattling effect.
Check the distance between the back wall of the refrigerator and the wall of the room. If the gap is too small, the vibration of the compressor is transmitted directly to the wall, which begins to resonate. A distance of at least 5-10 cm is considered optimal for free air circulation and vibration damping.
Also inspect the shelves inside the refrigerator. Glass shelves that are not fully installed in the grooves, or bottles that are placed close to each other, can ring and knock at the slightest vibration of the case. It is enough to correct the contents to eliminate this type of noise.
| Sound type | Probable cause | Localization | Urgency of repair |
|---|---|---|---|
| Rhythmic knocking | Compressor malfunction | Bottom, rear | High |
| Crackling/Rustling | Fan or ice | Freezer | Average |
| Gurgling | Refrigerant in the pipes | Throughout the entire body | Normal |
| Glass clinking | Vibration of shelves | Inside the chamber | Low |
Hydraulic shock in the refrigerant system
Sounds reminiscent of water pouring or gurgling are often frightening inexperienced users, but in most cases they are absolutely normal. This is how it behaves refrigerantcirculating through the tubes of the system. However, if the sound becomes loud and accompanied by a knocking sound, this may indicate a pressure problem or the presence of an air lock.
In rare cases, the cause of loud water hammer is a malfunction of the valves or throttle valve. If the refrigerant does not have time to evaporate or condense in the required areas of the circuit, shock waves arise that are transmitted to the metal tubes. This phenomenon requires professional diagnostics using pressure gauges.
It is worth noting that in modern models with environmentally friendly refrigerants the nature of the sounds may differ from old Soviet refrigerators that ran on freon. New gases can create higher noise frequencies when passing through the narrow channels of the capillary tube.
When you need to call a technician
There are a number of symptoms in which self-repair is not only ineffective, but also dangerous. If the knocking is accompanied by a complete lack of cold, a burning smell, or visible sparks in the compressor area, you must immediately stop using the device. Further work may result in a fire.
Also, the help of a specialist is required if, after defrosting and checking the fasteners, the sound does not disappear. This indicates a deep mechanical failure of internal components, such as the compressor valve group or the damper gear motor. An attempt to disassemble the sealed circuit yourself will lead to final breakdown of the unit.
It is important to understand that modern refrigerators are full of electronics. Errors in diagnostics can lead to failures in control boards. If you are not confident in your abilities, it is better to entrust the repair to certified specialists who have access to original spare parts.
⚠️ Attention: Opening the compressor yourself or breaking the tightness of the refrigerant circuit is prohibited by the legislation of many countries and requires special equipment for gas recovery.
Is it normal for the refrigerator to make clicking noises when turned on?
Yes, this is absolutely normal. The click sounds from the start relay, which starts the compressor. If the clicks become very frequent (every few seconds) and the refrigerator does not turn on, this is a sign of a malfunction of the start relay or the compressor itself.
Why does the refrigerator knock only at night?
During the day, extraneous noise can be masked by the household background. At night, in silence, even the normal operation of the unit becomes audible. Also, at night, the voltage in the network may drop, which affects the operation of the electric motors, making their sound more booming.
Can a new refrigerator knock?
A new refrigerator may make sounds when first started until the system reaches operating mode. Also, the internal fastenings may have become dislodged during transportation. If the knocking does not go away after 24 hours of operation, contact the service center under warranty.
Is knocking in the compressor dangerous?
A dull, rhythmic knocking sound in the compressor area often indicates wear of the piston group or connecting rod mechanism. Operating in this mode will lead to jamming of the motor and costly repairs, so this sound cannot be ignored.