A sudden knock or loud rumble coming from the kitchen can disturb the peace at any moment. The refrigerator, which just yesterday worked silently, suddenly begins to make frightening sounds, making you think about a serious breakdown. Most often, the source of noise is the compressorheart of the refrigeration unit, which is responsible for the circulation of the refrigerant.
Understanding the nature of these sounds allows you not to panic ahead of time and make an informed decision about calling a technician or self-diagnosis. It is important to distinguish a normal operating hum from alarm signals indicating wear of parts or violation of operating conditions.
In this article we will analyze in detail the mechanics of knocking, analyze the main causes of malfunctions and provide a clear algorithm of actions for the owner of household appliances. You will find out when you can do with prevention, and when urgent replacement of components is required.
⚠️ Attention: If the knocking is accompanied by a burning smell, sparking or a complete cessation of cooling, immediately disconnect the device from the power supply to avoid a short circuit or fire.
The mechanics of the compressor and the nature of the noise
To understand why knocking occurs, it is necessary to briefly consider the design of a modern motor-compressor. Inside the sealed metal casing there is an electric motor that drives the piston group. This entire structure is suspended on special springs that dampen vibrations during operation.
In normal mode, you hear a smooth, monotonous hum. It occurs due to the movement of refrigerant through the pipes and vibration of the motor windings. However, if depreciation the internal components are damaged or worn out, the character of the sound changes. Metal clanging, rattling or rhythmic knocking are direct signs of mechanical contact of parts that should not normally be in contact.
Particular attention should be paid to the moment of start-up. In the first seconds after switching on starting relay it gives a powerful impulse, and the engine rotor should start moving. If at this moment there is a loud click or blow, followed by silence, it means that the motor cannot start and is trying to turn the shaft against an obstacle.
Excessive vibration can be transmitted to the body of the refrigerator itself if it is not level. In this case, the compressor works properly, but resonates with the floor surface or cabinet walls. Checking the stability of the unit is the first step in diagnosing any noise.
Main causes of knocking during operation
There are several key factors that provoke the appearance of extraneous sounds. They can be divided into operational (user-dependent) and technical (related to wear or defects).
One of the most common reasons is imbalance. If the refrigerator is placed on an uneven floor, the body will warp. This causes the internal springs on which the compressor is suspended to experience an uneven load. As a result, during operation, the motor begins to hit the walls of the casing, producing a characteristic metallic knock.
Another important aspect is the condition pipelines. The copper tubes through which freon circulates are located in close proximity to the compressor. Over time, constant vibration may cause the fasteners to loosen, and the tubes will begin to touch each other or the motor housing. This contact gives rise to a loud, loud rattling sound, which is often confused with the knocking of the unit itself.
- 🔧 Loosening the compressor mounting bolts leads to displacement of the unit and impacts on the walls.
- 📉 Wear of the piston group inside the motor causes dull knocks during compression strokes.
- 🧊 The formation of an ice plug in the capillary system can create a water hammer.
- 🔌 Electrical problems, such as sparking relay contacts, give a sound effect similar to a crack.
⚠️ Warning: Do not attempt to open it yourself sealed compressor casing. Inside there is refrigerant under pressure, and a leak in the seal will make further repairs impossible without special equipment.
It is also worth considering the age of the equipment. In older models, wear on the motor shaft bearings is inevitable. When the lubricant dries out or becomes contaminated with oil breakdown products, the shaft begins to play, which causes severe noise and vibration. Modern inverter models compressors work differently, but they are also subject to mechanical wear, although to a lesser extent.
Diagnostics: normal hum or dangerous knock
The ability to distinguish between types of sounds is a critical skill for the owner household appliances. Not every noise indicates a breakdown. The operating sound of a working refrigerator is low-frequency and uniform. It can intensify during active cooling and subside when the set temperature is reached.
The alarm should be sounded if you hear sharp, abrupt sounds. A metallic clanging sound, reminiscent of a hammer striking iron, indicates that something inside the motor has come loose or broken. If the knocking is accompanied by strong vibration, which can be felt by touching the body, this indicates a serious imbalance.
For an accurate diagnosis, you can perform a simple test. Move the refrigerator away from the wall to allow access to the back wall. Turn on the device and listen. Try to gently (observe safety precautions!) press the tubes coming from the compressor with your hand. If the sound has changed or disappeared, then the problem is vibration of the pipelines.
| Sound type | Probable cause | Degree of danger | Required actions |
|---|---|---|---|
| Smooth humming | Normal motor operation | Safe | No action required |
| Metal clanging | Destruction of internal components | Critical | Replacing the compressor |
| Sounding rattling noise | Touching the tubes or housing | Medium | Adjust the tubes, check the fasteners |
| Clicks when start | Malfunction of the starting relay | High | Replacement of the relay |
It is also important to monitor the cyclic operation. If your refrigerator hums longer than usual or turns on too often, this may be an indirect sign of compression problems. In such cases, the motor operates with overload, which accelerates its wear and can lead to knocking soon.
Problems with the starting relay and electrical system
Often the reason that the refrigerator makes strange sounds is not the motor itself, but its starting system. Start relay is a device that supplies a starting impulse to the motor windings. If it is faulty, the contacts may stick or burn, producing a characteristic crackling or clicking sound.
Typical symptoms look like this: a loud click is heard, the motor tries to start, hums for a few seconds, then another click follows, and the motor goes silent. After some time, the cycle repeats. This process is called “cycling” and is extremely harmful to the motor windings, as it can lead to their burnout.
In some cases, the relay may simply rattle during operation due to poor contact or vibration. Replacing this element is one of the most common and inexpensive procedures in refrigerator repair. However, if the relay is working properly and the knocking noise persists, the problem lies deeper.
Checking electrical circuits requires skills in working with a multimeter. It is necessary to ring the motor windings for short circuits or breaks. If the resistance of the windings is normal, but the motor hums and does not start, the rotor may be jammed.
How to check the starting relay?
Remove the relay from the compressor (usually it is secured with latches on the side). Shake it near your ear. If something dangles and rattles inside, the relay is faulty (the starting tablet or mechanism has collapsed). Also visually inspect the contacts for the presence of carbon deposits.
Wear of internal components and water hammer
The most unpleasant scenario is mechanical destruction inside the containment zone. Pistons, connecting rods and valves operate at high speed. If the oil has lost its properties or its level has dropped, the rubbing parts begin to wear out. A backlash appears, which turns into a knock.
The so-called hydraulic hammeroccupies a special place. It occurs when liquid freon instead of gaseous freon enters the compressor cylinder. The liquid does not compress, and the piston hits it with a bang. This causes a dull, powerful blow, which can quickly disable the piston group.
The reasons for the ingress of liquid freon can be different: a malfunction of the thermostat, which does not allow the motor to turn off in time, or problems with the capillary tube. As a result, the refrigerant does not have time to completely evaporate in the evaporator and is sucked back into the compressor in the form of liquid.
- 🛑 Jamming of the piston group due to lack of lubrication.
- 🔨 Destruction of the valve plate leads to popping noises and decreased performance.
- 🌡️ Overheating of the motor due to poor ventilation causes metal expansion and jamming.
- 💧 Moisture entering the system (often after poor-quality repairs) causes corrosion and knocking.
If you hear something loose inside the compressor, like a nut in a jar, this is a sure sign of connecting rod separation or bearing failure. Operating such a refrigerator is impossible and dangerous.
Instructions: what you can do yourself
Before calling a technician, try to perform a number of simple steps that can eliminate the noise if it is not associated with an internal breakdown of the motor. Remember that any work should only be carried out with the appliance disconnected from the network.
First, check the installation of the refrigerator. It must stand strictly horizontally. Use a building level or just rock the body. If there is misalignment, adjust the height of the legs. Often this will immediately eliminate the vibration hum.
Then inspect the rear of the unit. Make sure that the refrigerator is not placed close to the wall. The gap should be at least 10-15 cm for normal air circulation. Check that the tubes are not touching each other. If you find a point of contact, carefully (without using force!) separate them or lay a piece of foam rubber.
☑️ Do-it-yourself noise diagnostics
If the noise remains, you can try replacing the starting relay if you are confident in your abilities. It is inexpensive and sold in parts stores. However, if the problem is in the compressor itself, independent repair is impossible without a vacuum pump and soldering skills.
⚠️ Attention: Technical specifications and location of components may vary depending on the model. Always check the manufacturer's technical documentation before interfering with the design.
When you need to call a specialist
There are situations when independent actions are useless and even harmful. If diagnostics show that the knocking comes from inside the sealed casing, or if replacing the relay does not help, professional repairs are required.
The technician will conduct a full diagnostic, measure the current consumption and pressure in the system. If the compressor has died, it must be replaced. This is a complex process that includes unsoldering old tubes, installing a new motor, evacuation of the system and refilling with freon.
Also, the help of a specialist is needed if the capillary tube needs to be overcooked or the filter drier needs to be replaced. These works require special equipment and knowledge. An attempt to do this “on the knee” will result in the refrigerator either not working or completely breaking down in a short time.
Do not ignore the increasing noise. Timely repairs can save the compressor from complete destruction. If you hear changes in the operation of the equipment, do not wait until it stops freezing - this can lead to food spoilage and more expensive repairs.
Why does the refrigerator hum loudly only after defrosting?
After defrosting, excess moisture may remain in the system, which enters the compressor, causing noise. The body could also shift due to manipulation. Let the device work for several hours, the noise should subside. If not, check whether the water in the sump has frozen.
Is it possible to lubricate the compressor if it starts knocking?
No, it is impossible to lubricate the compressor from the outside. The oil is contained within a sealed circuit. If you hear a knocking sound due to a lack of oil, it means that it has either burned out, got into the system, or jammed. The unit needs to be replaced.
How much does it cost to replace a compressor?
The cost consists of the price of the unit itself, the cost of the technician’s work, materials (freon, filter, solder) and transportation. The price may vary depending on the model of the refrigerator and the region.
Is the knocking of the compressor dangerous for others?
The sound itself is not dangerous, but it signals a malfunction. If the compressor jams while the network is running, the wiring may burn out or a fire hazard may arise. Therefore, it is not recommended to leave a running, knocking refrigerator unattended.