A sudden crackling sound or periodic knocking in the operation of a refrigeration unit always causes concern among owners of household appliances. Refrigeration compressorbeing the heart of the system, in normal mode it should operate relatively quietly, emitting only a uniform hum. The appearance of extraneous sounds, especially those reminiscent of crackling, clicking or metallic clanging, indicates that changes have occurred in the operation of the mechanical or electrical part.
Such symptoms cannot be ignored, since motor-compressor is the most expensive component, the replacement of which is often economical not practical compared to the cost of a new refrigerator. Understanding the nature of the sound allows you to determine whether an urgent call to a technician is required, or whether the problem can be solved by simply adjusting the position of the housing. In this article we will analyze in detail the mechanics of noise and methods for eliminating it.
Physics of noise: how a compressor works and where the crackling comes from
To understand the cause of the sound, it is necessary to imagine the internal structure of the unit. Inside the sealed casing there is an electric motor that drives a piston that forces the refrigerant. In good condition, all moving parts are lubricated with special oil, and the body itself is suspended on springs to dampen vibrations. Crackling occurs when the balance between moving parts is disturbed or the nature of the passage of gases changes.
Often the sound is associated with hydraulic shock. If liquid (non-freon vapor, namely oil or liquid refrigerant) enters the system at the time of startup, the piston encounters resistance from an incompressible medium. This causes a characteristic dull crack or thud. The source may also be discharge valvewhich, when worn or deformed, begins to knock on the valve plate seat.
⚠️ Attention: If the cracking sound is accompanied by strong vibration of the housing and burning odors, immediately disconnect the device from the power supply. Continuing operation may lead to jamming of the piston group and failure of the motor.
It is important to distinguish between operating noise and emergency noise. Short clicks when the thermostat turns off is normal, the relay is working. But if a crackling noise is heard while the motor is running, this indicates mechanical friction or impact. Vibration can be transmitted to the system tubes, causing them to collide, which is also perceived as a crackling sound.
Natural causes: when a crackling sound is normal
Not every sound indicates a breakdown. Modern refrigerators, especially those with No Frostsystem, have a complex design, where many elements are subject to thermal expansion. Plastic parts of the internal housing, the evaporator and even the condensate tray can make sounds resembling crackling or crackling when the temperature changes.
Such sounds often occur when the compressor is turned off or immediately after it starts, when the temperature difference is maximum. This phenomenon is called the thermoacoustic effect. The material contracts or expands, and if there is a microscopic gap or tension somewhere, a click is heard. This is absolutely normal for household appliances and does not require intervention.
How to distinguish thermoacoustics from a breakdown?
Thermoacoustic crackling is usually short, does not repeat often and does not depend on the load on the motor. The mechanical crackling sound of a compressor is often rhythmic, increases over time, or is accompanied by vibration.
In addition, new models of refrigerators can “break in.” During the first weeks of operation, the lubricant in the compressor is distributed unevenly, which can cause slight noise. However, if unit starts to crack after years of service, you should look deeper for the cause.
Mechanical faults: wear of parts and fasteners
One of the most common causes of loud cracking and knocking is wear of the compressor suspension elements. The motor inside a metal casing is mounted on special springs. Over time, the metal of the springs can tire, burst, or simply shift. As a result, during operation, the motor begins to hit the walls of the casing, producing a loud metallic clang or crackling sound.
Also, the problem may lie in the wear of the motor shaft bearings. When the bearings reach the end of their service life, play appears and the shaft begins to warp. This leads to the rotor touching the stator, which causes not only noise, but also the risk of a short circuit. Bearings cannot be separately replaced in sealed units, the entire assembly requires replacement.
Another mechanical factor is the loosening of the bolts securing the compressor to the frame of the refrigerator. Vibration gradually loosens the threaded connections. If the compressor “walks” on the frame, it may touch adjacent tubes or the cabinet body. Diagnostics is simple: you need to carefully (without touching the hot parts if the refrigerator has just been running) shake the compressor with the power off. If you hear a knock, the fastenings are loose.
Problems with the electrical part and the starting relay
The sounds produced by starting relayare often mistaken for the crackling sound of the compressor. This small block is responsible for starting the engine. If the relay contacts are burnt or oxidized, an electric arc occurs when you try to start, which is accompanied by a loud cracking sound. The motor at this moment may hum, but not start, after which the relay clicks and turns off the power.
In modern inverter models, the situation is more complicated. There, the launch is controlled by an electronic unit. The inverter converter itself can produce a cracking sound if the voltage in the network is unstable or the capacitors are faulty. Electric arc Inside the relay - this is dangerous, as it can lead to melting of the contacts and complete failure of the starting system.
To check the relay, it is often enough to remove it and shake it. If the sound of broken parts (ceramic core) is heard inside, the element is faulty. Replacing the relay is a simple procedure and often eliminates the problem of false “motor crackling.”
Hydraulic hammer and problems with refrigerant
A dangerous phenomenon that causes a dull crackling sound is water hammer. This happens when liquid enters the compressor cylinder instead of gaseous freon. The liquid is incompressible, and the piston, trying to compress it, encounters rigid resistance. This is accompanied by shock and cracking of the valves.
The reasons for liquid ingress can be different:
- ❄️ Excess of refrigerant in the system after unqualified repairs.
- ❄️ Malfunction of the thermostatic valve (TRV), which supplies too much frequency for the compressor. Several such impacts can break the valve plate or connecting rod. If you suspect this problem, operation should be stopped.
- ❄️ Freezing of moisture in the system, which then thaws and enters the compressor.
- ❄️ An attempt to start the compressor immediately after defrosting or transportation (oil has flowed into the system).
⚠️ Attention: Water hammer is critically dangerous for the compressor. Several such impacts can break the valve plate or connecting rod. If you suspect this problem, use should be discontinued.
Crackling noise may also occur when operating on a mixture of gases if refueling was carried out without evacuating the system. The presence of air or other impurities changes the physical properties of the working environment, causing detonation and noise. Freon must circulate in its pure form, without impurities.
Diagnostics and methods of elimination with your own hands
Before calling a technician, initial diagnosis can be made. It will help you understand the scale of the problem. Start with a visual inspection and a noise level check. Make sure that the refrigerator is level, the height adjustment legs are screwed in, and the body does not touch furniture or walls.
☑️ Primary diagnosis of noise
If the problem is vibration of the tubes, you can carefully (with caution, copper is very brittle!) bend it by hand or place a piece of foam rubber between them. If the crackling noise comes from the compressor itself and is associated with its beating against the casing, sometimes tightening the mounting bolts helps. However, if the internal springs are worn out, this method will only give a temporary effect.
The table below shows the main symptoms and probable causes:
| Sound pattern | Probable cause | Necessary actions |
|---|---|---|
| Loud metal clanging | Broken motor suspension spring | Replacing the compressor or springs (difficult) |
| Crackling noise when starting, the motor does not start | Faulty starting relay | Replacing the start relay |
| Thud, vibration | Water hammer, valve wear | System diagnostics, compressor replacement |
| Short clicks, crackling | Thermal expansion of plastic | Normal, no intervention required |
| Rhythmic knocking inside the casing | Wear of shaft bearings | Replacing the compressor |
If simple methods (leveling, insulating tubes) do not help, and the sound increases, professional repairs are required. An attempt to independently open the sealed compressor casing at home impossible and dangerousas it requires special tools and soldering skills.
Prevention and extension of service life
To minimize the risk of mechanical noise and crackling, it is important to follow the operating rules. Do not allow the compressor to overheat: leave a gap between the back of the refrigerator and the wall for free air circulation. Dust on the condenser (black grille at the back) also impairs heat transfer, causing the motor to overload.
Avoid turning the device on and off frequently. After defrosting or transporting, allow the refrigerator to stand upright for several hours before turning it on to allow the oil to drain into the compressor crankcase. A sharp start with a “dry” motor is a sure way to scuffing and crackling.
⚠️ Attention: The characteristics of oils and types of refrigerants in modern refrigerators may differ from older models. When making repairs, it is important to use compatible materials, otherwise the noise and damage will recur.
Regularly check the tightness of the door. If the seal is worn out and warm air enters the chamber, the compressor is forced to work almost non-stop. Long-term continuous operation leads to overheating, expansion of parts and knocking.
When a compressor replacement is necessary
If diagnostics showed wear of the valve group, jamming of the piston or breakage of the internal spring, repair is often impractical. The cost of replacing the “internals” (mechanical part) is often comparable to purchasing a new unit, and the reliability of such repairs is questionable.
In such cases, the entire motor-compressor is replaced. This is a complex procedure that requires:
- 🔧 Unsoldering the old compressor and installing a new one.
- 🔧 Replacing the filter-drier (required when opening the system).
- 🔧 Evacuating the circuit to remove moisture and air.
- 🔧 Refilling with the exact amount of freon.
After replacement, the technician must check the tightness of the connections and the operation of the system in different modes. A properly installed new compressor will operate quietly and efficiently for many years. Do not try to save on calling a specialist when it comes to replacing the main unit.
Frequently asked questions (FAQ)
Can you continue to use the refrigerator if the compressor starts to crack?
If the crackling is weak and is associated with vibration of tubes or thermoacoustics, you can. If a clear metallic knock, clanging or crackling noise is heard during startup, operation is dangerous. The motor can jam at any moment, which will lead to the winding burning out and the need for expensive replacement.
Why does a new refrigerator crack when operating?
New models often make sounds due to the operation of the No Frost system (air circulation), expansion of plastic parts during the first cooling, or the operation of an inverter compressor that changes the speed. If the cracking sound is not accompanied by loss of cold, this is normal.
How much does it cost to replace a compressor?
The cost consists of the price of the unit itself (depending on the brand and power), the cost of the work of the technician, refilling with freon and travel. On average, this is a significant amount, so the feasibility of repairing an old refrigerator must be assessed individually.
Can a relay crack instead of a compressor?
Yes, this is a very common reason. The start relay makes loud clicking and cracking noises when trying to start. If the motor hums for 2-3 seconds, then there is a crackling sound and it goes silent - with a 90% probability the problem is in the relay or motor windings, and not in the mechanics of the compressor itself.