A sudden knocking sound in the refrigerator can disturb the silence in the house and cause anxiety in the owner of expensive equipment. This sound is often ignored, believing that the equipment is simply “working”, however, extraneous mechanical shocks are rarely the norm for a working unit. Extraneous noise may indicate both banal instability of the case and serious internal breakdowns.
In this article we will analyze in detail the mechanics of the occurrence of knocking so that you could independently carry out the initial diagnosis. Understanding the source of the sound will help you decide whether you need to call a technician or whether the problem can be fixed in five minutes on your own.
Sometimes refrigeration equipment makes sounds that seem like knocking, but are not. For example, gurgling of refrigerant or cracking of plastic during thermal expansion are normal processes. However, rhythmic knocks, ringing of metal or dull shocks require immediate attention.
Violation of installation rules and housing geometry
The most common reason why a refrigerator knocks lies not in the internal components, but in improper installation. If the body of the unit is skewed, vibration from the running motor is transmitted to the floor and walls, causing resonance. Vibration causes the doors or internal shelves to come into contact with the body, creating a rhythmic knock.
Check the position of the refrigerator: it should be strictly vertical. Even a slight tilt forward or sideways disrupts the operation of the compressor suspension and causes runout. Use a building level to check. Adjusting the legs allows you to set the equipment perfectly level.
Pay attention to the distance to the walls and furniture. If the refrigerator is placed close to cabinets, vibration can be transmitted to them, causing nearby objects to rattle. The gap should be at least 5-10 cm on all sides.
⚠️ Attention: Do not try to place cardboard or wooden blocks under the legs for leveling. They will quickly collapse under the weight of the unit, which will lead to distortion and increased knocking. Use only standard adjustable screw supports.
Faults of the compressor and start relay
The heart of the refrigerator is the compressor, and it is this that most often becomes the source of mechanical sounds when worn out. If you hear a loud metallic knocking, clanging or banging sound from the lower part of the housing, the problem is probably in the piston group engine.
During normal operation, the compressor hums evenly. A knock appears when the gaps between rubbing parts are broken or when a valve breaks. In this case, the motor works with overload, trying to pump freon, which leads to the piston hitting the cylinder walls.
Another reason for knocking in this area is a faulty start relay. This small element is responsible for starting the engine. If its contacts are stuck or the mechanism is worn out, when you try to start, a loud click is heard, followed by a buzzing sound and a second click (attempt to restart). Relay It can simply hang on the compressor housing, creating rattling.
How to distinguish the knocking sound of a compressor from another noise?
Put your hand on the body of the running motor. If you feel a strong, “evil” vibration and hear impacts from inside the metal casing, this is wear on the internal components. If the sound comes from outside (from tubes or relays), the nature of the vibration will be different.
Diagnostics of the compressor requires caution. If the unit hums but does not start, and then a knock is heard and it turns off, the thermal protection relay has tripped. This is a sign that the motor is “dying” or jammed.
Problems with refrigerant circulation and capillary tube
Sometimes knocking in the refrigerator is caused not by mechanical parts, but by the movement of the refrigerant. If a plug forms in the system or circulation is disrupted, the liquid may hit the walls of the tubes with force. This is often accompanied by gurgling, but with strong pressure it turns into distinct blows.
Particular attention should be paid to the capillary tube. If it is displaced and touches the compressor housing or other metal parts, vibration turns this contact into a constant ringing or knocking. Heat transfer in such places it is disrupted, which reduces the cooling efficiency.
Let's consider the main symptoms of problems with refrigerant and tubes in the table:
| Symptom | Probable cause | Sound character | Necessary actions |
|---|---|---|---|
| Loud bubbling and knocking | System clogged or air | Gurgling, turning into blows | Call a technician for cleaning |
| Metallic ringing | Touching of the tubes on the body | High-frequency rattling | Bend the tube (carefully!) |
| Whistling and knocking | Freon leakage | Hissing turning into knocking | Searching for leaks and refilling |
| Rhythmic clicks | Thermostat operation | Quiet clicks every 10-15 minutes | Normal (does not require repair) |
It is important to understand that the circulation system is under pressure. Independent intervention in a sealed circuit without special equipment and skills can lead to complete failure of the equipment.
Vibration of internal elements and defrosting
Often the source of irritating sound is objects inside the chambers. Glass shelves, drink bottles or plastic containers may resonate with motor vibration. Check that the food does not touch the walls of the refrigerator.
A special case is the No Frost system. In such models, the fan and heater are turned on periodically. If too much ice has formed on the evaporator, the fan blades may touch ice. This causes a loud cracking or knocking noise that gets louder when the door is opened (since the fan usually stops). ice, the fan blades may touch ice. This causes a loud cracking or knocking noise that gets louder when the door is opened (as the fan usually stops).
To fix the problem in the No Frost system, a complete defrost is often required. Leave the refrigerator turned off with the doors open for 24 hours. If after turning on the sound disappears, then the problem was in the ice. If the knocking returns after a week, the defrost sensor or heating element is faulty.
- 🧊 Check whether the drawers are frozen to the back wall.
- 🥤 Remove bottles and cans away from the walls of the chambers.
- 🌬️ Listen to see if they are touching the fan blade has an ice crust.
It is also worth checking the fastenings of the shelves. If the glass shelf is loose or its guides are loose, they will bounce when the compressor operates.
Wear of shock absorbers and engine mounts
The compressor in modern refrigerators is mounted on a suspension consisting of springs and rubber shock absorbers. Over time, rubber dries out, cracks or tears. As a result, the engine begins to “hang out” and hit the metal casing or frame of the refrigerator.
This is one of the most common causes of strong knocking in older models. Depreciation ceases to fulfill its function of damping vibrations. This can be seen visually if you look at the bottom of the unit (removing the back cover): the compressor can hang on one spring or lie on tubes.
Replacing shock absorbers is a simple procedure, but requires access to the motor. It is necessary:
- Disconnect the refrigerator from the network.
- Remove the rear metal panel.
- Inspect the rubber bushings and suspension springs.
- Replace damaged elements with new ones.
☑️ Compressor suspension diagnostics
Sometimes the reason The knocking sound is caused by loosening of the mounting bolts of the compressor itself. They just need to be tightened with a wrench of the appropriate size.
⚠️ Attention: Before touching the tubes and compressor mounts, make sure that the refrigerator is disconnected from the power supply for at least 10-15 minutes. High pressure remains in the system, and careless movement can lead to injury or depressurization.
When knocking is normal and when a repairman is needed
Not every sound requires repair. Modern refrigerators, especially those with inverter compressors, can make specific sounds when the operating power changes. Quiet knocking of valves or fluid flow is acceptable if they are not accompanied by loss of cold.
However, there are a number of signs when you should not hesitate. If the knocking is accompanied by engine heating, lack of cooling or a burning smell, operation must be stopped. Inverter compressor If a breakdown occurs, it can be very expensive, so early diagnosis saves the budget.
A summary table of situations will help you make a decision:
| Situation | Urgency | Action |
|---|---|---|
| Quiet knock on startup | Low | Observation |
| Loud clanging and floor vibration | Medium | Check installation and suspension |
| Knock + no cold | High | Call technicians |
| Knock + burning smell | Critical | De-energize and call service |
Remember that constant operation of equipment in overload mode (which is often masked by knocking) reduces its service life significantly. It’s better to check it once than to change the compressor after six months.
The myth about the “development” of a new refrigerator
There is an opinion that a new refrigerator should knock during the first weeks of operation while the parts “grind in.” This is not true. The new unit should operate quietly. A knock immediately after purchase is a sign of a defect during transportation or a manufacturing defect.
Prevention of noise
In order for the refrigerator to enjoy silence for many years, it is important to follow simple operating rules. Regular defrosting (for drip systems) prevents ice from forming on fans and pipes. Cleaning the condenser from behind from dust helps the motor not to overheat and run smoother.
Do not overload the shelves with heavy objects. Excess weight creates additional stress on the frame, increasing resonance phenomena. Arrange the dishes so that they do not touch each other and the walls.
Timely replacement of door seals also affects operation. If the door does not close tightly, the compressor works longer and harder, trying to build up the temperature, which increases wear and tear and the likelihood of a knock.
Frequently asked questions (FAQ)
Why does the refrigerator make a knock only at night?
At night, the apartment is quieter, and the sounds become more noticeable. In addition, the power supply voltage may drop at night, causing the compressor to work intermittently or make a louder noise. Also, at night, the structures of the house may cool down, and sounds from neighbors or pipes can be heard better.
Is it possible to operate a refrigerator if it is knocking?
For a short time - it is possible if the sound is quiet and associated with the installation. But if the knock is loud, metallic or accompanied by vibration, long-term operation will lead to destruction of the compressor suspension, broken pipes and expensive repairs.
Does an inverter refrigerator knock?
Inverter models are quieter than usual ones, since they do not have sudden starts and stops. However, if a knock appears in them, this almost always indicates a mechanical malfunction of the fan or wear of the compressor bearings.
How to silence the knock of a compressor yourself?
It is impossible to completely silence the knock of a faulty compressor. You can only reduce vibration by placing a rubber mat under the legs of the refrigerator or moving the tubes away from the body. The cardinal solution is to replace the shock absorbers or the motor itself.