A sudden knock in the refrigerator can frighten any owner of household appliances, especially if the unit previously worked quietly and unnoticed. Extraneous sounds are often the first signal that the cooling system has failed or some part has worn out. Such manifestations should not be ignored, since a malfunction noticed in time can save the compressor from an expensive replacement.
The nature of the noise can be very different: from a banal distortion of the housing to serious problems with the motor-compressor or defrost system. In some cases, the sound occurs due to vibration transmitted to furniture or the floor, while in others it indicates water hammer in the system. Understanding the nature of the sound and the conditions under which it appears will help you quickly diagnose the problem.
In this article we will look in detail at the main reasons why the refrigerator started knocking and look at troubleshooting methods. You will learn when you can deal with a problem yourself, and in which cases it is better to call a specialist. It is important not to panic, but to consistently analyze the situation so as not to aggravate the situation with incorrect actions.
Primary diagnosis: nature and localization of sound
Before grabbing the tools, you need to determine exactly where the sound comes from and what its character is. Localization of noise is a key stage of diagnosis. Try to go to the refrigerator and listen: is it knocking from below, where the compressor is located, or is the sound coming from inside the chamber? Owners often confuse knocking with buzzing or crackling, which leads to incorrect conclusions.
Pay attention to the frequency of sounds. If the refrigerator makes a knocking noise only when the motor is turned on or off, this may indicate thermal expansion of materials or the operation of the start relay. Constant metallic clanging or rhythmic knocking during operation most often indicates mechanical problems.
⚠️ Attention: If the knocking is accompanied by strong vibration of the housing, immediately check the stability of the installation of the unit. Prolonged operation in this mode can lead to breakage of the cooling system tubes.
It is also important to assess whether the temperature inside the chambers has changed. If, in addition to knocking, you notice that food has become worse to freeze or, conversely, freezes slightly, the problem is systemic in nature. In this case, refrigerator diagnostics requires a more in-depth approach, possibly using measuring instruments.
Installation problems and external factors
One of the most common reasons why a refrigerator knocks or hums is improper installation. If the unit is not level, resonance occurs, increasing any operating vibrations of the compressor. Check the horizontal installation using a building level. Adjusting the height of the legs often helps eliminate vibration noise completely.
The second important point is the distance to walls and furniture. The rear grille of the condenser should not touch the wall, and the side walls should not touch the cabinets. The minimum distance should be 5-10 cm to ensure normal air circulation. If the refrigerator is moved close, the vibration is transmitted to the building structures, creating a booming knocking effect.
- 🔧 Check the adjusting screws on the front legs and tighten them for alignment.
- 📏 Move the refrigerator from the wall at least 10 centimeters.
- 🧱 Make sure that nothing touches the radiator grille from behind.
- 🧼 Check if foreign objects (bottles, jars) have fallen behind the refrigerator.
Sometimes a knock is made objects located inside the chambers or on the door shelves. Heavy glass jars placed close together may rattle when the compressor vibrates. Remove any unnecessary items from the shelves and check if the sound has disappeared. If the noise disappears, then the problem was not in the equipment, but in operating conditions.
Malfunction of the compressor and start relay
The compressor is the heart of the refrigerator, and it is it that most often becomes the source of noise. If you hear a loud metallic knocking or clanging noise specifically at the lower rear of the unit, the problem may lie in the motor itself. Wear on the internal valves or piston group causes the parts to start hitting each other. In such cases compressor repair usually impractical, its replacement is required.
Another common cause of knocking is a malfunction of the starting relay. This small element is responsible for starting the engine. If its contacts are burnt or the mechanism is jammed, when you try to start, a loud click is heard, followed by a hum and a second click. The motor cannot start, and after a few seconds the thermal protection is activated, opening the circuit.
Some models, especially older ones, use a compressor with internal suspension. If the springs on which the motor is suspended inside the casing are stretched or burst, strong vibration and knocking on the walls of the casing occurs during operation. This requires opening the casing and replacing the springs or the entire unit assembly.
How to check the starting relay?
Remove the relay from the compressor contacts and shake it. If a ringing sound is heard inside (as from broken glass or a piece coming off), then the part is faulty and requires replacement. Also visually inspect the contacts for carbon deposits.
It is worth noting that modern inverter compressors operate much quieter, but they are not immune to breakdowns. If inverter refrigerator makes strange sounds, this may indicate problems with the electronic control unit or the engine itself.
Knock in the No Frost system and problems with the fan
In refrigerators with a system No Frost The fan circulates cold air. If you hear a rhythmic knocking or cracking sound coming from deep inside your freezer or refrigerator, this is most likely the problem. The fan blades could touch frozen ice or a foreign object.
Often this problem occurs after defrosting, if the owner did not allow the unit to dry completely, or due to a malfunction of the defrosting system. Ice builds up on the evaporator and interferes with the rotation of the impeller. In this case, refrigerator fan makes a characteristic crackling sound, which intensifies when the door is opened (since in many models the fan stops when the door is opened).
| Symptom | Probable cause | Actions |
|---|---|---|
| Crackling inside the chamber | Ice on the fan blades | Complete defrosting (24 hours) |
| Humming from the bottom back | Contamination capacitor | Cleaning the grill with a vacuum cleaner |
| Clicks at start | Malfunction of the starting relay | Replacing the relay |
| Vibration of the case | Incorrect installation | Adjusting the legs |
To fix the problem, it is often enough to completely defrost the refrigerator within 24 hours. This will allow the ice to melt and free up space for the fan to operate. If, after defrosting, the knocking returns after a few days, it means that the operation of the defrosting system (heating element, timer or sensor) is disrupted.
☑️ Actions in case of fan noise
Hydraulic shock and gurgling in the pipes
Sometimes the knocking noise that the user hears is actually the sound of refrigerant moving through the pipes. In a professional environment, this phenomenon is called “liquid knock”. If moisture gets into the system or freon does not completely evaporate in the evaporator, the liquid phase of the refrigerant enters the compressor, causing valve shock.
This is a serious problem that can quickly damage the compressor. The sound is usually described as dull thuds or gurgling turning into knocking. Hydraulic hammer is dangerous because liquid, unlike gas, is not compressed, and its entry into the compressor cylinder leads to mechanical damage.
⚠️ Attention: It is strictly forbidden to try to remove moisture from the cooling system yourself. The system needs to be evacuated and the filter-drier replaced at a service center.
Also, knocking can occur due to improper filling of the refrigerator with freon. If the repairman pumped too much or too little refrigerant during the last repair, this disrupts circulation and causes noise. In such cases, you need to call a specialist to measure the pressure and refill.
Vibration of pipelines and fasteners
Over time, the vibration that occurs during compressor operation can weaken the fastening elements of the internal tubes. The copper tubes through which freon circulates are fixed to the body or frame with special holders. If the fasteners are loose, the tubes begin to bang against each other or against the wall of the refrigerator, producing a loud metallic knock.
You can often fix this problem yourself if you have access to the back of the unit and remove the protective casing. It is necessary to carefully find the contact point and install a soft gasket or bend the tube so that it does not touch other parts. However, this must be done extremely carefully so as not to damage the thin-walled tubes and not to break the tightness of the system.
In addition, it is worth checking the fastenings of the compressor itself. The bolts that hold it in place can become loose over time. Tightening them (without fanaticism, so as not to break the thread) often eliminates low-frequency hum and rattling.
When you need to call a specialist
Not in all cases you should try to fix the refrigerator with your own hands. If you have checked the installation, defrosted the unit, removed unnecessary items, and the knocking does not stop, most likely the problem is serious. It is especially alarming if the knocking is accompanied by an increase in temperature in the chambers or a complete failure of the equipment.
A specialist call is necessary if:
- 🛠️ A metallic clanging sound is heard inside the compressor.
- 🔥 The compressor gets very hot and does not turn off.
- ❄️ The cold has stopped forming, but the motor is working.
- 💧 Traces of oil have appeared under the refrigerator.
Professional diagnostics of refrigerators allows you to accurately determine the unit that requires replacement. The technician uses a pressure gauge station to check pressure, a tester to check electrical circuits, and a thermal imager to look for leaks. Attempts to independently repair complex components without experience can lead to final breakdown of the unit.
⚠️ Attention: If the refrigerator is under warranty, any independent repair or even simply removing seals will lead to loss of warranty. In such cases, immediately contact an authorized service.
Timely contacting a service center can save significant money. Replacing a start relay or fan is inexpensive, while replacing a compressor that has burned out due to overload is one of the most expensive procedures in repairing household appliances.
Preventing noise and extending service life
In order for the refrigerator to operate quietly and for a long time, it is important to follow the operating rules. Regular defrosting (even for the No Frost system, preventive shutdown once a year is recommended) helps to avoid ice build-up. Cleaning the rear grille from dust ensures effective heat transfer and reduces the load on the motor.
Do not put hot food in the refrigerator - this causes a sharp increase in load on the system and can lead to water hammer. Make sure that the food does not touch the back wall of the chamber where the evaporator is located. Following these simple rules will help to avoid a situation where the refrigerator knocked requires repair.
Compressor service life
The average service life of a modern compressor is 10-15 years. However, with constant overload (work under wear and tear in a hot room, dirty condenser), this period can be halved.
Remember that silence in the operation of the refrigerator is a sign of its serviceability. Any new sound is a signal that the equipment gives to the owner. Attentive attention to these signals allows you to keep household appliances in working order for many years without emergency and expensive repairs.
Why does the refrigerator knock only at night?
At night, the level of background noise in the apartment decreases, and the sounds of operating appliances become more noticeable. In addition, the power supply often drops at night, which can make it difficult for the compressor to start and cause the relay to click louder. Also, neighbors work more quietly at night, and vibration can be transmitted more strongly through the building's structures.
Is it possible to operate a knocking refrigerator?
Short-term operation is possible if the knocking is caused by vibration or objects inside. However, if the knocking noise comes from the compressor or system, prolonged operation will aggravate the breakdown. It is better not to take risks and carry out diagnostics so as not to be left without products and equipment.
How much does it cost to replace a compressor?
The cost of replacing a compressor consists of the price of the unit itself and the work of the technician. Depending on the model of the refrigerator and the region, the price can vary from 5 to 15 thousand rubles and more. In some cases, repairs are not economically feasible, and it is easier to buy new equipment.
How often do you need to defrost the refrigerator?
Refrigerators with a drip system require defrosting as ice forms (usually 1-2 times a year). No Frost systems do not formally require defrosting, but manufacturers recommend disconnecting them from the network for a day once every 1-2 years for prevention and hygiene.