The situation when the refrigerator begins to make an obsessive, loud hum is familiar to many owners of household appliances. This sound can be a subtle background noise or a powerful humming noise that keeps you awake at night. Most often, the source of vibration and sound waves is compressor the heart of any refrigeration system, responsible for the circulation of the refrigerant.
Understanding the nature of this sound is critical for deciding whether an urgent call for a technician is required or the problem can be solved independently. In some cases, the hum indicates a normal, albeit loud, operating mode, in others it indicates critical wear of components or a violation of operating rules that requires immediate intervention.
In this article we will analyze in detail the mechanics of noise occurrence, methods of primary diagnosis and troubleshooting methods. You will learn to distinguish harmless sounds from the harbingers of a serious breakdown, which will help extend the life of your equipment Indesit, Bosch or Atlant.
Physics of sound: how a compressor works
In order to understand why the motor hums, you need to understand the principle of its operation. The compressor is a sealed unit containing an electric motor, a piston group and valves. When voltage is applied, the rotor begins to rotate, setting in motion pistons that compress the gaseous refrigerant and push it through the pipeline system.
The process of gas compression is inevitably accompanied by vibration and a characteristic low-frequency hum. This is a physical feature of the work of any piston compressors. Modern models use inverter motors, which are quieter, but even they are not completely devoid of sound. The hum is transmitted from the motor housing to the metal casing, and then through the frame to the body of the refrigerator itself.
The intensity of the sound directly depends on the load on the system. The greater the difference between the set temperature and the current temperature in the chamber, the more active the engine is. The noise level is also affected by the quality of the refrigerant and the condition of the oil in the system.
⚠️ Attention: If the hum is accompanied by a metallic clanging, knocking or crackling sound, this is not normal operation of the compressor. Such sounds indicate mechanical destruction of internal components or the entry of foreign objects.
It should be taken into account that the noise level is regulated by technical standards. For most household models, a level of up to 40 dB is considered the norm. Exceeding this threshold often indicates an imbalance or resonance phenomena.
Why do old refrigerators hum louder?
Older models running on R12 freon often had a less effective noise reduction system and noisier compressors with a start relay. In addition, over the years of operation, the shock absorbers wore out, and the oil in the system lost its properties, which increased friction and, as a result, the noise level.
External factors: installation and ventilation
Before suspecting a breakdown of internal components, it is necessary to exclude external causes. Often the reason that the refrigerator is humming is due to improper installation. If the equipment is installed unevenly, a misalignment occurs, which leads to vibration of the case and increased resonance.
The most important aspect is the gap between the back wall of the refrigerator and the wall of the room. The compressor heats up during operation and requires free air circulation to cool. If the refrigerator is moved close to the wall or furniture, the heat is not dissipated, the motor overheats and begins to work with increased load, producing a louder hum.
- 🔧 Check the horizontal installation using a building level and adjust the legs.
- 🌬️ Provide a gap of at least 5-10 cm from the back wall to the nearest one obstacles.
- 🏗️ Make sure that the floor can support the weight of the equipment and does not have defects that cause vibration.
It is also worth checking whether the refrigerator pipes (especially the capillary tube and discharge pipe) do not touch the cabinet walls or other objects. The vibration of a running motor is transmitted to the pipes, and they, in turn, begin to rattle against the furniture, creating the illusion of a motor malfunction.
Problems with shock absorption and compressor mounting
The compressor inside the refrigerator is mounted on a special frame using shock absorbers. These can be springs or rubber cushion feet. Their task is to dampen vibrations that occur during engine operation. Over time, the rubber dries out, cracks or completely breaks down, and the springs can weaken or rust.
When shock absorption is impaired, the metal compressor casing begins to vibrate with greater amplitude. In the worst case, if the mounting bolts are loose, the motor may hit the walls of the refrigerator body. This causes a loud, increasing hum and a characteristic knock when starting or stopping.
Diagnosis of this problem is simple: you need to carefully remove the back cover of the refrigerator (after unplugging it!) and visually inspect the fasteners. If the rubber bushings are crumbled or missing, they must be replaced. Sometimes it is enough to simply tighten the mounting bolts if they have become loose due to vibration.
☑️ Diagnostics of compressor mounting
Faults in the starting relay and electrical part
Starting the refrigerator engine controlled by the start relay. This small block is responsible for supplying voltage to the stator windings at the time of start. If the relay is faulty, the contacts may burn or stick, resulting in a humming sound without starting the engine or a heavy, strained humming sound when trying to start.
You can often hear a situation where the refrigerator hums for 5-10 seconds, then there is a click and the motor goes silent. After some time, the cycle repeats. This is a classic symptom of a malfunction starting relay or protective thermal relay. The motor tries to start, but cannot gain speed, which is why the current consumption increases and the protection is triggered.
In some cases, a hum may be caused by problems with the voltage in the network. If the voltage drops below the permissible level, the electric motor cannot develop the required power, which causes low-frequency hum and overheating of the windings.
| Symptom | Probable cause | Sound character |
|---|---|---|
| Humming and clicking | Malfunction of the starting relay | Rhythmic hum with periodic clicks |
| Constant monotonous hum | Wear of bearings or shock absorbers | Uniform low-frequency noise |
| Humming and heating of the case | Motor overload or poor ventilation | Strained, loud sound |
| Whistling or hissing | Freon leak or blockage | High-frequency sound accompanying hum |
| Metal clanging | Destruction of the internal components of the compressor | Loud knocking, grinding |
⚠️ Attention: Replacing the start relay requires observing the polarity connections. Incorrect installation of a new relay may result in burnout of the compressor windings. If you are not confident in your skills, it is better to contact a specialist.
Mechanical wear and water hammer
The most unpleasant scenario is the mechanical destruction of compressor components. Inside the sealed housing there are rubbing pairs: a piston and cylinder, a shaft and bearings. During prolonged use without proper maintenance or when working in extreme conditions (frequent power surges, overheating), wear of these parts occurs.
If the shaft bearings are worn out, a characteristic howling or humming sound appears, the tonality of which can vary depending on engine speed. If the piston group wears out, the compressor may begin to “knock.”
Another reason is hydraulic hammer. This occurs when liquid refrigerant or oil enters the compressor cylinder in large quantities when the piston is at top dead center. The liquid is incompressible, and the piston hits it with force, which causes a loud sound and can lead to damage to the valves or connecting rod.
Restoring such a compressor at home is impossible. It requires either replacement of the unit with a new one or complex professional repairs involving overhaul of the motor, which is often not economically feasible.
Specifics of inverter operation compressors
Inverter compressors are increasingly used in modern refrigerators. Unlike traditional ones, they do not turn off completely, but only change the engine rotation speed. This allows you to maintain the temperature more accurately and save energy.
However, inverter motors can produce a specific high-frequency hum or whistle, which is absent in conventional models. This is the sound of the inverter board and electric motor operating at high speeds. In most cases, this is a variant of the norm inherent in the design.
However, if the inverter refrigerator begins to hum louder than usual, this may indicate problems with the control board or that the system is operating in maximum power mode due to a freon leak or a loosely closed door.
What is the difference between the hum of an inverter and normal?
A normal compressor hums cyclically: it turns on - it hums, reaches temperature - it goes silent. The inverter produces an even sound that varies in tone, which can last for hours, since it rarely stops completely.
When you need to call a technician
Independent repair of the refrigerator is possible only in cases related to the installation, cleaning or replacement of easily accessible parts such as a lamp or rubber bands. If the problem lies within the system, qualified assistance is required.
A technician is needed if, after checking external factors and fastenings, the hum does not disappear. Also an alarming signal is the appearance of a burning smell, strong heating of the compressor or a complete absence of cold when the engine is running.
Professional diagnostics include checking the pressure in the system, the current strength of the motor windings and the integrity of electrical circuits. Only with the help of special equipment can you accurately determine whether the compressor can be repaired or requires replacement.
Why does the refrigerator hum immediately after defrosting?
After defrosting, the refrigerator may hum louder than usual, since it is loaded with warm food and works at full power to gain temperature. Also, residual water in the tray can cause vibration. If the hum does not subside after 3-4 hours, check to see if water has gotten into the electrical parts.
Is it possible to lubricate a humming compressor?
No, the refrigerator compressor is a sealed unit. There are no grease fittings or holes for lubrication. An attempt to drill a hole for lubrication will lead to depressurization of the system, leakage of freon and final breakdown of the unit.
Is it normal for the refrigerator to hum when first turned on?
Yes, when first started or after a long stay, the compressor may work louder. This is due to the fact that the oil may have drained to the lower part of the system, and it needs time to be evenly distributed over the friction units. Usually, after 30-60 minutes of operation, the noise returns to normal.
Does the amount of products affect the noise level?
Indirectly - yes. A full refrigerator stays cold longer and the compressor turns on less often. An empty refrigerator heats up faster, causing the motor to work more often. However, a sharp increase in the volume of the hum during loading may indicate resonance of dishes or containers inside the chambers.