A sudden knocking sound in the refrigerator can unsettle any owner, especially if the device has been operating silently for years. Extraneous sounds, such as clicks, crackling or rhythmic tapping, are often the first signal that changes have occurred in the cooling system or the mechanics of the unit.
Before you panic and call a technician, it is necessary to carry out an initial diagnosis, since many sounds are absolutely normal for the operation of modern equipment. Understanding the physics of the processes occurring inside the chamber and in the engine compartment will allow you to distinguish normal operation from a serious breakdown that requires immediate intervention.
In this article we will analyze in detail the mechanics of noise, consider the design features of various models and give step-by-step instructions for eliminating vibrations without calling service.
Physics of sounds: normal operation of the compressor and refrigerant
Many owners mistake the sounds that it makes compressor during normal operation as a breakdown. Modern inverter motors can operate almost silently, but classic models with a piston operating principle always produce vibration when starting and stopping. At the moment of startup, the piston creates a sharp shock, which is transmitted through the frame to the body, causing a dull blow.
In addition to engine mechanics, the source of sound is often the refrigerant itself. Freon circulating through the evaporator and condenser tubes can make sounds reminiscent of water flowing or slight gurgling. This is due to a change in the state of aggregation of the substance when passing through the capillary tube and expansion valve.
It is also worth taking into account the thermal expansion of materials. Plastic panels inside the chamber and metal elements contract or expand with a sharp change in temperature, producing a characteristic cracking sound similar to clicks.
⚠️ Attention: If the knocking is accompanied by a complete cessation of cold or the appearance of puddles under the device, this may indicate a freon leak or compressor failure. In such cases, operation is prohibited.
It is important to distinguish the nature of the sound: a uniform hum with periodic clicks of the thermostat is the norm. A rhythmic metallic clang or squeal indicates a mechanical malfunction.
Particular attention should be paid to models with the system No Frost. They have a built-in fan that can hum or knock if ice has formed on its blades or if it touches the wiring.
Structural reasons: distortions and vibration of the case
One of the most common reasons why a refrigerator knocks is a banal violation of installation rules. If the unit is not level, vibration from the running motor is transmitted to the floor and amplified by resonance. Even a microscopic misalignment can cause the cabinet to touch nearby objects or furniture.
Check the adjustment feet on the bottom of the device. They must be unscrewed so that the refrigerator stands stable and does not wobble from side to side. It often happens that one of the legs does not reach the floor, and the entire weight falls on three points of support, which causes severe distortion of the frame.
Also check the distance to the walls and cabinets. The rear grille of the condenser heats up during operation and may expand slightly, and the vibration of the motor may cause the case to make micro-movements. If the refrigerator is moved close to the wall, it will tap rhythmically against it.
Do not forget about the internal shelves. If glass or plastic elements are not secured tightly in the grooves, they will vibrate in response to the operation of the compressor. Remove all products and shelves, start the unit - if the knocking disappears, the problem has been found.
To eliminate vibration, you can use special anti-vibration pads under the legs, which dampen vibrations and prevent sliding.
☑️ Diagnostics of the refrigerator installation
Problems with the compressor: wear and mechanical defects
When it comes to serious breakdowns, the first thing they suspect is compressor. If the engine is worn out, its internal parts (pistons, connecting rods, valves) may have play, which causes a metallic knock during operation. This often happens in old models of refrigerators that have been in service for more than 10-15 years.
Another reason is the weakening of the mounting bolts holding the compressor to the frame. Vibration gradually unwinds the threaded connections, and the motor begins to “walk” in its seat, hitting the walls of the casing or tube.
In some cases, knocking occurs due to the fact that the copper tubes approaching the compressor touch each other or the motor housing. When the engine starts, they begin to vibrate and make a loud clanging sound. This can easily be corrected by carefully straightening the tubes or installing a damper between them.
If you hear a loud pop at startup followed by a humming noise, this may indicate problems with the start relay or an attempt to start a “stuck” motor. In such a situation, it is better to immediately disconnect the device from the network.
⚠️ Attention: Repairing a compressor requires specialized tools and skills in working with refrigerants. Opening the engine compartment on your own can lead to injuries and permanent breakdown of the equipment.
Diagnostics of the condition of the motor often requires listening through a technical tube or using a stethoscope to identify the exact source of vibration inside the casing.
No Frost system: fan and ice
In refrigerators with system No Frost a fan located in the freezer compartment or behind the back wall is responsible for the circulation of cold air. If you hear a crackling sound that turns into a hum, or periodic knocks, most likely the problem is in this unit.
A common cause is ice freezing on the evaporator. Pieces of ice can break off and fall under the fan blades, causing a characteristic cracking sound (“as if a bone had gotten into a meat grinder”). Ice can also build up on the fan axis, blocking its rotation.
Another option is wear of the bearings of the fan itself. Over time, the lubricant dries out and the bushing begins to make noise. In some models, the fan may move and touch the housing of the plastic air duct box.
For diagnostics, complete defrosting of the refrigerator is often required. If after 24 hours of defrosting without connecting to the mains, the noise disappears, then the problem was ice freezing. If the sound remains, the fan will need to be replaced.
Pay attention to the condition of the drainage system. If the water drainage hole is clogged, moisture remains inside and freezes, forming large ice crystals, which subsequently interfere with the operation of the mechanisms.
Thermoregulator and electrical clicks
Rhythmic clicks, repeated with a certain periodicity, often come from the thermostat. This device is responsible for turning the compressor on and off when the set temperature is reached. The mechanical contact switch inside the thermostat makes a sound similar to a thump.
If the clicking sounds become too loud or frequent, the thermostat may be faulty or incorrectly set. In electronic models, the control relay may click, but this happens quieter and less frequently.
Sometimes clicks occur due to poor contact in the electrical circuit. Oxidation of contacts or loose terminals can cause micro-discharges that sound like a crackling noise. This is dangerous and requires inspection by an electrician.
It is important to distinguish the sound of the thermostat from the sound of thermal expansion. The thermostat clicks only when the motor is turned on or off, and the plastic cracks chaotically during operation.
Replacing a thermostat is a simple procedure, but requires selecting an analogue with exactly the same parameters, otherwise the refrigerator will not work correctly (not freezing enough or working without stopping).
Diagnostic table: determine the malfunction by sound
To make it easier to find the cause of the noise, use the following table. It will help classify the sound and determine the likely breakdown.
| Sound type | Probable cause | Elimination method | Difficulty |
|---|---|---|---|
| Thud when starting/stopping | Normal compressor operation | Not required, this is the norm | No |
| Metal clanging, vibration | Touching the tubes or loosening the fasteners | Bend the tubes, tighten the bolts | Low |
| Crackling, turning into humming | Fan No Frost (ice or wear) | Defrosting or replacing the fan | Medium |
| Rhythmic clicks | Thermoregulator | Checking contacts, replacing | Average |
| Strong vibration of the case | Incorrect installation, misalignment | Adjustment legs, checking the floor | Low |
Analysis of the nature of the sound allows you to save time and money, since in many cases expensive repairs are not required.
If after all the checks the source of the noise is not found, and the sound intensifies, it is better to contact professionals for an in-depth diagnosis.
FAQ: Frequently asked questions
Why does a new refrigerator knock loudly?
New units may make more noise due to the tight packing of the compressor shipping bolts (if they have not been removed) or because the internal parts have not yet been ground in. Also check that all shipping tapes and foam plastic have been removed from the inside.
Is it dangerous if the refrigerator starts knocking after defrosting?
If the knocking appears immediately after turning on, you may have damaged the tubes or the fan during defrosting. If the sound appears after a few hours, it is possible that the ice did not have time to completely melt and got into the mechanisms. Let the device stand turned off for a few more hours.
Is it possible to lubricate a compressor if it knocks?
No, modern compressors are sealed and do not require maintenance. Attempting to drill a hole for lubrication will result in freon leakage and failure. If the motor knocks due to wear, it is replaced entirely.
Does the floor level affect the noise of the refrigerator?
Yes, an uneven floor is one of the main causes of resonant hum and knocking. Use a building level and adjustable legs for perfect installation.
What to do if an Indesit or Atlant refrigerator knocks?
For models Indesit i Atlant a “gurgling” sound is characteristic due to the design of the capillary tube - this is the norm. If you hear a metallic clang, check the motor mount, since in these models the rubber shock absorbers become dull over time.