Suddenly appeared A knock in the refrigerator can unsettle any person, especially if it is heard in the silence of the night. This sound often indicates that a malfunction has occurred in the unit, which requires the immediate attention of the owner. Ignoring extraneous noise can lead to more serious damage and costly repairs of the entire cooling system.
Before you panic or call a technician, you need to conduct initial diagnostics yourself. Often the reason lies in trivial things that can be fixed in a few minutes without special tools. However, there are situations when compressor vibration or a malfunction of internal components requires professional intervention.
In this article we will analyze in detail all the possible causes of knocking, rumble and clattering. You will learn how to distinguish a normal operating sound from a sign of a breakdown, and receive step-by-step instructions for troubleshooting yourself.
Primary diagnosis: normal sound or breakdown?
Modern refrigerators, especially models with a system No Frost, make many different sounds during operation. This is due to the circulation of refrigerant, the operation of fans and the periodic activation of various mechanisms. It is important to learn to distinguish between normal noise and alarm signals.
The quiet hum of the engine, the periodic gurgling of freon in the pipes and light clicks of the thermostat when switching modes are considered normal. If you hear a loud metal clanging, rhythmic knocking or strong vibration of the housing, this is a cause for concern. A critical sign is a change in the nature of the sound when you lightly press the housing or change the position of the unit.
First, listen to where exactly the sound is coming from. If the noise is localized at the bottom, there is most likely a problem with the compressor or its mountings. If the sound is heard from the top of the chamber, you should pay attention to the fan or defrost system.
Try to gently press the side wall or back panel with your hand. If the knocking stops, then the problem is the resonance of the housing or poor fastening of the internal elements. In this case, the situation is not critical and can often be solved by adjusting the legs or rearranging the contents.
Installation problems and external factors
One of the most common reasons why the refrigerator knocks or vibrates strongly is improper installation. The unit must stand on a flat, hard surface. If the floor is uneven or the legs are not adjusted, the case warps, which leads to a shift in the center of gravity and increased vibration of the motor.
Check whether the back of the refrigerator is touching furniture, walls or other objects. During operation, the compressor vibrates, and if there is no gap between the housing and the wall, resonance occurs, amplifying the sound significantly. Also make sure that the internal shelves and drawers do not touch each other or the walls of the chamber.
To eliminate these problems, follow these steps:
- 🔧 Level the position of the refrigerator by twisting the front legs until they are completely flush with the floor.
- 📏 Move the unit away from the wall at least by 5-7 cm to ensure free heat exchange.
- 🥤 Remove all objects lying on the top lid of the refrigerator that can rattle.
Sometimes food becomes the source of noise. Glass bottles or jars placed close to each other on a shelf may jingle at the slightest vibration. Rearrange them so that they do not touch.
Malfunctions of the compressor and start relay
The compressor is the heart of the refrigerator, and it is it that most often becomes the source of loud sounds when there is a malfunction. If you hear a loud knocking sound when starting followed by silence, or a rhythmic knocking sound during operation, the problem may be with the motor itself or the starting protection relay.
The starting relay is responsible for starting the engine. If its contacts are oxidized or the mechanism is worn out, when voltage is applied, a shock occurs, accompanied by a loud click or knock. In some cases, the relay may simply “stick”, causing a buzzing sound and subsequent knocking when trying to start.
The compressor itself may knock for the following reasons:
- 🔨 Wear of the internal motor mounts, which causes it to start beating against the housing.
- 🔩 Loosening of fasteners bolts securing the compressor to the frame.
- ⚙️ Water hammer caused by liquid freon entering the cylinder.
⚠️ Attention: If you suspect a compressor malfunction, do not try to repair it yourself without skills in working with electrical equipment. Attempting to replace the relay requires disconnecting from the network and observing safety precautions.
To diagnose the compressor, it is often necessary to remove the rear panel. Visually inspect the motor: if it is skewed or loose on the mounts, it is necessary to tighten the bolts or replace the shock-absorbing pads. If the knocking comes from inside the motor housing, it will most likely need to be replaced.
☑️ Compressor diagnostics
Failure of the No Frost system and fan
In refrigerators with an automatic defrosting system, the fan is a common source of noise. It circulates cold air. If ice freezes on the blades or in the area of the fan motor, a characteristic cracking or knocking sound occurs, similar to the operation of a propeller touching a foreign object.
A knocking noise can also occur when the defrost heater is operating. When heated, metal elements expand and may make clicking sounds. This is normal, but if the sound is too loud and repeats frequently, it is possible that the defrost sensor is not working correctly and the ice does not have time to completely melt, interfering with the operation of the fan.
To check the condition of the fan, you must:
- Defrost the refrigerator completely (at least 24 hours).
- Remove the plastic panel in freezer compartment.
- Manually rotate the fan blades - they should rotate freely, without jamming.
- Check whether the ice has frozen on the motor body.
If after defrosting the sound disappeared, but after a couple of days it appeared again, it means the defrost cycle is broken. This may be due to a faulty timer, temperature sensor or heater. In this case, diagnostics of the electrical circuit is required.
Why does ice interfere with the fan?
The ice coat on the evaporator gradually grows and reaches the fan blades. When rotating, the blades hit the ice, emitting a loud cracking sound and gradually collapsing.
Table for diagnosing sounds and probable causes
To simplify troubleshooting, use the table by comparing the nature of the sound with the possible cause. This will help you more accurately describe the problem to the technician or understand what part to look for in the store.
| Sound type | Probable cause | Localization | Difficulty of repair |
|---|---|---|---|
| Loud click when startup | Faulty start relay | Rear, bottom | Low |
| Rhythmic knocking/trembling | Incorrect installation, touch walls | All over the body | Minimum |
| Crackling in the freezer | Ice on the fan (No Frost) | Inside the chamber | Average |
| Metal clanging | Wear of compressor suspensions | Rear, below | High |
| Gurgling and overflow | Normal circulation of freon | Through tubes | Not required |
Please note that in older refrigerator models, sounds may be louder due to design features and wear and tear of materials. If your unit is more than 10 years old, the appearance of new noises may signal the natural aging of components.
When you need to call a specialist
There are a number of situations when independent repair is not only ineffective, but also dangerous. If you do not have special knowledge in the field of electrical engineering and refrigeration equipment, it is better not to take risks.
Be sure to contact a specialist if:
- 🆘 After knocking, the refrigerator stops freezing or turning on.
- 🔥 You smell burning or see sparking in the area compressor.
- 💧 Traces of oil or indicator liquid have appeared under the unit.
- 🔌 The knock is accompanied by knocking out plugs or circuit breakers in the electrical panel.
⚠️ Attention: Opening the sealed circuit of the cooling system without a license and special equipment is prohibited. This can lead to freon leakage and final breakdown of the unit.
A professional technician will carry out diagnostics using instruments, check the pressure in the system, the resistance of the compressor windings and the serviceability of the electronics. This will allow you to accurately determine the cause and eliminate it with a guarantee.
Noise prevention and extending service life
In order for the refrigerator to operate quietly and for a long time, it is important to follow the operating rules. Regularly check the cleanliness of the condenser (grids at the back), as dust and animal hair impair heat transfer and cause the motor to overload.
Do not overload the refrigerator with food, make sure that the door closes tightly. Once every six months, check the reliability of the shelves and drawers. If you notice that the refrigerator has begun to make more noise than usual, do not delay searching for the cause.
Compliance with the temperature regime also affects the operation of the unit. Do not place hot foods in the chamber and do not place the refrigerator near heat sources (stove, radiator). This will reduce the load on the compressor and reduce the likelihood of vibrations.
Does a flat floor affect energy consumption?
Yes, a skewed refrigerator creates additional load on the compressor and oil drainage system, which can increase energy consumption by up to 10-15%.
Why does the refrigerator knock only when turning on?
A knocking sound when turning on is most often associated with the starting relay or water hammer in the compressor. At the moment of start, maximum pressure is created, and if there is play or valve malfunction, a blow is heard. This can also be a normal sound of pressure equalization if it is quiet and single.
Is it possible to operate a knocking refrigerator?
If the knocking is caused by vibration of the housing or food, it is possible. If the compressor or relay knocks, operation is possible for a short time, but the risk of final breakdown is high. If there is an odor or there is no cold, use is prohibited.
How to lubricate a compressor if it is knocking?
Modern compressors are sealed and maintenance-free. It is impossible to lubricate them “from the outside”. Attempting to drill an oil hole will result in freon leakage and failure. If the compressor is knocking from the inside, it needs to be replaced.
Does the filling level of the chambers affect the noise?
Yes, an empty refrigerator can be noisier due to resonance. The products act as acoustic dampers. However, an overcrowded refrigerator also puts a strain on the air circulation system, which can increase fan noise.