Suddenly A knocking sound in the refrigerator can turn a cozy kitchen into a source of constant irritation. This sound not only breaks the silence, but also serves as the first alarm signal that a malfunction has occurred in the operation of complex climate control equipment. Ignoring such “symptoms” is dangerous, since seemingly insignificant noise may hide a serious breakdown of expensive components. Modern models, whether quiet or popular, operate almost silently in normal mode. The appearance of a rhythmic or chaotic knocking indicates an imbalance in the engine, wear of the bearings or problems with the circulation of the refrigerant. In this article, we will analyze in detail the mechanics of the occurrence of extraneous sounds and help you determine whether the problem can be fixed on your own or whether you need to call a specialist.
Modern models, whether quiet Liebherr or popular Indesit, operate almost silently in normal mode. The appearance of a rhythmic or chaotic knocking indicates an imbalance in the engine, wear of the bearings or problems with the circulation of the refrigerant. In this article, we will analyze in detail the mechanics of the occurrence of extraneous sounds and help you determine whether the problem can be fixed on your own or whether you need to call a specialist.
Before you panic, it is worth conducting an initial diagnosis. Often the source of sound is not the unit itself, but external factors: improperly installed equipment in contact with the walls of furniture, or vibration of nearby dishes. However, if you are convinced that the case is level and does not touch anything, and the knocking continues, then it’s time to look “inside” the device.
Primary diagnosis: external factors and installation
Before you grab the tools, you need to exclude trivial causes. Vibration of the case is the most common culprit of noise, which is easy to accept for the knocking of internal mechanisms. If the refrigerator is not level, the compressor causes resonance during operation of the entire structure, and it begins to “beat” the floor or kitchen unit. Check the legs: they should be unscrewed so that the device stands stable and sways slightly with a slight push, but does not wobble freely.
The second important point is the distance to the walls and furniture. The rear grille of the condenser heats up during operation and may be slightly deformed due to temperature, or simply vibrate. If the gap is less than 5 centimeters, a characteristic rattling knock occurs. Also check whether the walls of the refrigerator are touching adjacent cabinets or the washing machine.
- 🔍 Inspect the space around the unit for foreign objects that may rattle due to vibration.
- 📏 Measure the gaps between the body and the furniture - they should be at least 5-7 cm on all sides.
- ⚖️ Check the horizontal installation using a building level, even if everything seems level to the eye.
⚠️ Attention: If your refrigerator belongs to the system No Frost, make sure that the food inside the chamber does not touch the back wall. In the freezer, this can lead to freezing of food and subsequent knocking from the fan trying to turn the blades through the ice crust.
Sometimes the source of the sound is shelves or bottles inside. When the compressor operates, even microscopic vibration is transmitted to the contents. Remove all items and start the refrigerator empty. If the knocking noise disappears, the problem is solved. If the sound persists, then the problem is in the technical part.
Compressor: the heart of the refrigerator and the source of problems
If external factors are excluded, most likely the source of the noise is in the engine-compressor compartment. Compressor is the main unit that creates pressure for freon circulation. Newer models use inverter motors that operate almost silently, while older linear compressors make a clicking sound when starting and stopping, which is normal. However, a loud metallic knock is already a pathology.
One of the common reasons is wear of the internal valves or piston group. When the metal becomes thinner, play appears and the parts begin to hit each other with each cycle of operation. Also, knocking can occur due to the fact that the compressor itself is poorly secured to the frame. Over time, rubber shock absorbers dry out, crack or fly off, and the metal motor housing begins to hit the metal frame of the refrigerator.
Another critical situation is water hammer. If liquid freon enters the suction system instead of gaseous freon, a sharp shock occurs that can damage the valves. This often happens when the refueling is incorrect or the system is severely overheated/overcooled.
| Sound type | Probable cause | Degree of danger | Actions |
|---|---|---|---|
| Rhythmic metallic clanging | Piston group wear | High | Replacement of the compressor |
| Thud knocking on the body | Loose motor mounting | Average | Replacing shock absorbers |
| Quiet clicks at start | Relay operation (normal) | Low | Observation |
| Strong shock and humming | Hydraulic hammer or jamming | Critical | Urgent shutdown |
⚠️ Attention: If you hear a loud knock from the compressor area and at the same time feel that the refrigerator has stopped freezing, immediately turn off the device from the network. Further operation in this mode can lead to complete burnout of the motor windings and expensive repairs.
No Frost system: when the fan makes noise
In refrigerators with an automatic defrosting system (No Frost) fans are responsible for circulating cold air. Over time, malfunctions may occur in their operation, which are manifested as a characteristic knocking or crackling sound. Most often, the problem lies in freezing of the evaporator.
When the defrosting system fails (the heating element, defrost sensor or timer is faulty), a “fur coat” grows on the evaporator. The fan blades, rotating at high speeds, begin to touch this ice build-up. The sound resembles a trill or the frequent knocking of plastic blades on a hard surface. If the cause is not eliminated, the fan may jam completely or one of the blades may break.
The second reason is wear of the bearings of the fan itself. The bushing dries out, play appears, and when rotating the shaft begins to hit the motor body. This creates a monotonous but irritating knocking noise that intensifies as the engine warms up.
- ❄️ Check to see if ice has frozen on the back wall of the freezer.
- 🌀 Listen to whether the nature of the sound changes when you open the door (in some models the fan stops).
- 🛠️ Inspect the integrity of the fan blades (partial disassembly is required).
How to defrost the refrigerator for inspection?
Unplug the appliance, open the doors and leave for at least 12-24 hours. Place rags to catch water. If after complete defrosting the knocking noise disappears and appears again after a week or two, the problem is in the defrosting system (heating element or sensors).
It is worth noting that in dual-circuit systems No Frost fans can be installed in both the refrigerator and freezer compartments. Sound localization will help you understand which node requires attention. If the knock comes from above, most likely the problem is in the refrigerator compartment; if from below or behind, it is in the freezer.
Deformation of pipelines and capillary system
Copper tubes through which the refrigerant circulates are located along the entire perimeter of the refrigerator. During operation, due to thermal expansion and contraction, as well as vibration of the compressor, these tubes can move. If the distance between them or between the tube and the body becomes critically small, a collision occurs.
When the compressor starts, the pressure in the system increases sharply, causing pulsation of the pipelines. If they touch, you hear a loud metallic knock or rattle. This happens especially often in older models, where the factory insulation of the tubes may have dried out or been damaged during previous repairs.
Sometimes the cause is a capillary tube, which can vibrate at a high frequency. It is difficult to notice visually, but audibly it is defined as a high-frequency ringing. To eliminate it, you must carefully, taking precautions, bend the tubes away from each other or install additional damper gaskets.
⚠️ Attention: Copper is a soft metal. When you try to straighten the tubes with your own hands, it is extremely easy to damage or squeeze them. Any depressurization of the circuit will require a complex procedure for finding leaks, soldering and refilling with freon. If you are not confident in your abilities, it is better not to touch the tubes.
When knocking is the norm: features of the equipment
Do not forget that a refrigerator is a complex mechanism, and some sounds are inherent in the design. For example, in models with one compressor and a circuit switching solenoid valve, when switching from the cooling mode of the refrigerator compartment to the freezing mode, a distinct click or light blow is heard. This valve changes the direction of freon flow.
Cracking of plastic and internal walls when the temperature changes is also considered normal. Materials have different coefficients of thermal expansion, and when the compressor suddenly starts or stops, the housing can “play”, making sounds similar to tapping. This usually goes away after 15-20 minutes of operation.
Inverter compressors that operate continuously, changing power, can emit a hum, which sometimes modulates and is perceived as a periodic knock. It is important to distinguish these operating noises from the sounds of a breakdown: operating sounds, as a rule, are quiet, do not increase over time and are not accompanied by loss of cold.
- 🔊 A click when the engine stops is the work of the start-up relay.
- 🌡️ Cracking of walls is thermal expansion of materials.
- 💧 Gurgling and overflowing is the movement of freon through the system (normal).
Algorithm for eliminating noise yourself
If you decide fight the knock yourself, act consistently. First, carry out a complete defrost to eliminate the problem with ice in the system No Frost. Then check the installation and fastening of the compressor. To access the motor, you will need to remove the rear cover (in some models, the lower base).
Inspect the compressor shock absorbers. If they are intact, but the motor is loose, try adding additional washers or replacing the rubber bushings. Check if the tubes are loose. If the problem is in the fan, it can be removed, cleaned of ice and lubricated the bearing (if the design allows) or replaced entirely.
☑️ Action plan for knocking
If after simple steps (tightening the bolts, defrosting) the knocking does not stop, you probably need a professional diagnostics using a pressure manifold and a tester.
Prevention and care of the refrigerator
To extend the life of the equipment and avoid the appearance of extraneous sounds, it is important to follow the operating rules. Clean the condenser rear grille regularly to remove dust. The dust “felt boot” causes the compressor to work with overload, which leads to overheating and accelerated wear of parts, increasing the likelihood of knocking.
Make sure the door seals are tight. If warm, humid air enters the chamber, the system No Frost works harder, ice freezes faster, which again leads to problems with the fan. Wipe the seals with a soft cloth and check their fit.
Do not overload the shelves and make sure that the products do not touch the walls. Following these simple rules will help maintain silence in your kitchen and avoid costly repairs in the future.
Why does the refrigerator knock only when turned on?
A knocking sound when turned on is most often associated with starting currents and a sharp start of the compressor piston group. If the shock absorbers are worn out, the inertial jerk of the motor causes an impact on the body. This may also be a sign that the compressor is “difficult” to start due to problems with the start relay or a drop in voltage in the network.
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. These are the processes of grinding in parts and adapting materials to temperature conditions. However, a loud metallic knock is not typical for new equipment and may indicate a manufacturing defect or damage during transportation.
Is it dangerous to ignore the knock of a fan?
You cannot ignore the knock of a fan. If the blades rub against the ice or the housing, the fan motor will quickly burn out. In addition, impaired air circulation will lead to the fact that the refrigerator will no longer reach the desired temperature, the compressor will work without stopping, which threatens its overheating and failure.