The situation when the refrigerator knocks periodicallycan unsettle any owner of household appliances. At first, a quiet, barely noticeable sound can eventually develop into an obsessive rhythmic rumble that disturbs the peace in the apartment. Often, users ignore the first signals, believing that this is the norm for old equipment, but ignoring the problem can lead to serious damage to expensive components.
Extraneous sounds during the operation of the compressor or refrigerant circulation are always a symptom of an imbalance in the system. Vibration transmitted to housing, shelves or tubes, creating acoustic resonance. To understand why this happens in your case, it is necessary to carry out a detailed diagnosis, excluding the simplest everyday causes.
In this article we will analyze in detail the mechanical and physical causes of knocking. You will learn to distinguish between normal operating hum and dangerous signals that require specialist intervention. Timely detection the source of noise often allows you to avoid complex repairs and extend the life of the unit.
Natural sounds of refrigeration equipment
Before you hit alarm and disassemble the unit, it is worth making sure that the sounds produced are really a sign of a malfunction. Modern models, especially those with No Frost or Full No Frost, have a complex system of air circulation and automatic defrosting. Periodic plastic cracking or clicking may be completely normal.
As the temperature inside the chambers changes, the plastic elements of the housing and trays expand or contract. This process is accompanied by a characteristic crackling sound, which is often confused with knocking. Also, during operation of the compressor, refrigerant may flow through the tubes, which sounds like gurgling or a quiet hissing.
⚠️ Attention: If the knocking is accompanied by a sharp change in temperature in the chambers or the appearance of ice where it should not be, this is no longer a natural process, but a signal of a failure in the control or defrosting system.
A periodic click that is heard when the engine is turned on or off is also considered normal. This triggers thermal relay or the trigger device. If the engine tries to start, it makes a series of clicks, but does not turn on, and at the same time a loud knock is heard - this is a sign of a problem with the starting relay or the motor itself.
Vibration and unstable position of the unit
The most common, but common reason, why the refrigerator is knocking on the floor or adjacent furniture - this is an incorrect installation. Even high-quality equipment will vibrate if it is not level. During operation, the compressor creates vibrations that are transmitted to the legs and then to the base.
Check whether all four legs fit tightly to the floor surface. If the unit is on linoleum or tiles, even the slightest distortion will cause resonance. Vibration may increase if the refrigerator touches a wall or kitchen unit. In this case, the body will hit the furniture, creating a dull, rhythmic knock.
To eliminate this reason, it is not necessary to call a specialist. It is enough to make a simple adjustment:
- 🛠️ Check the horizontal installation using a building level, placing it on the top cover.
- 🔧 Tighten the adjustable screw supports so that the front legs are slightly higher than the back ones (for proper closing of the doors).
- 📏 Move the equipment at least away from the wall 5-10 cm to prevent contact of the case with the furniture.
Sometimes vibration occurs due to the fact that something inside the cameras vibrates in time with the operation of the motor. Check if bottles or cans are too close to the walls. Move them to the center of the shelf. Also make sure that the removable shelves fit tightly in the grooves and do not rattle.
Problem with the bushings and fastening of the compressor
If everything is in order with the installation, and the refrigerator continues to knockmost likely the problem is in the very “heart” of the unit - the compressor. The engine is mounted on the frame using special shock-absorbing bushings (dampers). Over time, the rubber of these elements drys out, cracks or completely collapses.
When the bushings fail, the metal housing of the compressor begins to touch the frame or other metal parts when starting and stopping. This causes a characteristic metallic clanging or knocking noise. In some cases, the engine may even “bounce” on the frame if the mounting bolts are loose.
Diagnosis of this malfunction requires caution. It is necessary to remove the rear protective panel and visually inspect the condition of the rubber bands. If they look flattened or cracked, they need to be replaced. It is also worth checking the tightness of the motor mounting bolts.
⚠️ Attention: Carry out any work on replacing bushings or repairing the compressor only after completely disconnecting the device from the power supply! Residual voltage or accidental starting can lead to injury.
Sometimes the knocking noise is not made by the motor itself, but by the tubes going to it. If they are too close together or touching the compressor housing, a ringing sound will be heard when they vibrate. Gently straighten the tubes by hand (being careful not to damage them), ensuring a gap.
Fan malfunctions in the No Frost system
In models with the system No Frost the fan is responsible for circulating cold air. If you hear a knocking sound coming from inside your freezer or refrigerator, this could be the problem. The fan blades may touch frozen ice or a foreign object.
A situation often occurs when ice freezes unevenly. A piece of ice crust may break off and get into the rotation zone of the blades. The result is a cracking or intermittent knocking noise that stops when the fan stops (usually when the door is opened).
Another reason is wear on the fan motor bearing. In this case, the sound will be more like a hum with periodic tapping. To fix the problem, you will need:
- ❄️ Completely defrost the refrigerator for 10-12 hours (it is best to leave it overnight).
- 🌀 Remove the back panel in the freezer to access the fan.
- 🧹 Clear the blades of ice and check for free rotation speed.
What will happen if you ignore the knock of the fan?
If the fan blade breaks and gets into the evaporator, this can lead to damage to the evaporator tubes and leakage of freon, which will require expensive repairs of the entire refrigeration system.
If after defrosting and cleaning the sound does not disappear, but when When rotating with your finger, you feel play or a grinding noise is heard, the fan will have to be replaced with a new one. This is a consumable item that wears out over time.
Water hammer and refrigerant problems
Sometimes users describe the sound as a “knock”, but in fact it may be water hammer in the refrigerant circulation system. This happens if liquid refrigerant enters the compressor instead of gaseous freon. The liquid is incompressible, and the compressor piston experiences shock load.
This situation is dangerous for the integrity of the compressor. It can occur if the system is not charged correctly (if repairs were previously made), if there is a strong excess of freon, or if the thermostatic valve is faulty. The sound is dull, heavy, and is often accompanied by strong vibration of the entire unit.
It is extremely difficult and dangerous to independently diagnose and fix this problem. Specialized equipment is required to measure the pressure and amount of refrigerant. If you suspect this particular reason, further operation of the device may finish off the compressor.
It is also worth noting the role of the capillary tube. If it is clogged or kinked, the pressure in the system is disturbed, which can also cause noise effects. However, more often in such cases the refrigerator simply stops freezing, and knocking is a secondary symptom.
Comparative table of causes and solutions
To systematize the knowledge gained and quickly determine the nature of the malfunction, use the table below. It will help to compare the type of sound with the probable cause.
| Sound type | Probable cause | Difficulty of repair | Required actions |
|---|---|---|---|
| Metal clanging when start | Wear of compressor bushings | Low | Replacement of rubber dampers |
| Crackling inside the chamber | The fan touches the ice | Average | Defrost, fan replacement |
| Rhythmic knocking on furniture | Incorrect installation | Minimum | Alignment of legs, move away |
| Thud, no cold | Water hammer, compressor breakdown | High | Call a technician, replace the motor |
| Clicks relay | Malfunction of the starting relay | Low | Replacement of the starting relay |
Please note that the complexity of the repair is indicated conditionally. If you have no experience with electrical appliances, even “low” complexity can be a problem. In such cases, it is better to turn to professionals.
Do not forget about the age of the equipment. If your refrigerator is more than 10-12 years old, some sounds may be a sign of natural wear and tear on rubbing parts. In this case, repairs may not be economically feasible compared to purchasing new equipment.
Prevention and operating rules
In order refrigerator to serve for a long time and work quietly, it is important to follow the operating rules. Regular defrosting (even for No Frost systems, preventive defrosting is recommended once a year) helps to avoid ice buildup on fans and sensors.
Make sure that food does not touch the back wall of the chamber, especially in the freezer. This not only creates unnecessary noise, but also disrupts air circulation, forcing the compressor to work harder. Also periodically check the cleanliness of the condenser (grids at the back) - dust and animal hair worsen heat transfer, increasing the load on the motor.
☑️ Annual noise prevention
When loading food, distribute it evenly. It is better to place heavy jars on the lower shelves, closer to the center. This will lower the overall center of gravity and reduce vibration when the compressor operates. Do not place hot foods inside - this causes a sharp rise in temperature and increased operation of the unit.
⚠️ Attention: Technical characteristics and design of refrigerators of different brands (Bosch, Indesit, LG, Samsung) may differ. Always check the user manual before disassembling the components of your specific model.
Frequently asked questions (FAQ)
Why does the refrigerator make a knocking noise only when turned on?
A knocking noise when turned on most often indicates a problem with the start relay or that the compressor “sits” on the frame due to worn bushings. At the moment of start, the vibration is maximum, hence the sound. If after warming up the knocking stops, most likely the problem is the resonance of the tubes or bushings.
Is it dangerous if the refrigerator knocks, but cools normally?
If there is cold, then the main cycle is not broken. However, constant vibration and knocking can lead to microcracks in the soldering of the tubes and eventual leakage of freon. In addition, this accelerates wear on the compressor bearings. It is not recommended to ignore it.
Is it possible to lubricate the compressor so that it stops knocking?
No, modern compressors are sealed units and do not require lubrication during operation. An attempt to drill a hole for lubrication will lead to depressurization and complete breakdown of the motor. Only fan bearings can be lubricated if they are removable.
How to distinguish the knock of a compressor from the sound of a fan?
The sound of a compressor is usually low-frequency, dull and comes from below the rear of the unit. The fan sound is higher frequency, crackling, and comes from inside the chambers (usually the freezer). To check, open the door: the fan should stop (in most models), but the compressor will continue to hum.
Is it worth replacing the compressor if it starts knocking?
If the knocking is caused by the destruction of the internal elements of the compressor (valves, piston group), then replacing the entire assembly is often economically justified only for new expensive models. For old appliances it is cheaper to buy a new refrigerator. An accurate diagnosis can only be made by a specialist with a pressure gauge station.