Why the refrigerator knocks: reasons, diagnosis and repair

Extraneous sounds from the refrigerator are always alarming. If the unit starts knocking, this is not just an annoying noise, but a signal of a possible malfunction. In most cases, knocking is associated with mechanical problems: vibration of the compressor, loose fasteners or problems in the refrigerant circulation system. But sometimes the reason lies in banal carelessness - for example, when the dishes come into contact with the walls of the chamber.

It is important to distinguish normal operating sounds (light humming, relay clicks) from abnormal ones (loud knocking, metallic clanging, rhythmic beats). The latter require immediate diagnosis. In this article we will analyze all the possible causes of knocking - from simple to serious, and also provide a checklist for checking it yourself. If you are not confident in your abilities, it is better to immediately contact a specialist: some malfunctions (for example, freon leak or failure of the motor-compressor) can lead to complete failure of the equipment.

Modern models (Samsung No Frost, LG Inverter Linear, Atlant with the Multi Air Flow system) knock more often due to design features: inverter compressors operate almost silently, but their fastenings become loose over time. In old refrigerators (ZIL, Minsk, Stinol), knocking is usually associated with wear of parts. Next is a detailed analysis of each reason with photos, diagrams and step-by-step instructions.

1. Compressor vibration: the most common cause of knocking

The compressor is the “heart” of the refrigerator, and its operation is always accompanied by a slight hum. But if the sound turns into rhythmic knocking or rattling, the problem lies in one of three factors:

• 🔧 The fastenings are loose. motor —over time, the bolts become loose, and the compressor housing begins to vibrate, hitting the frame.
• 🛠️ The shock absorbers are worn out —the rubber gaskets between the compressor and the refrigerator body lose elasticity and cease to dampen vibrations.
• ⚡ Electric motor malfunction —if the knocking is accompanied by overheating or shutdowns, wear of the bearings or an interturn short circuit is possible windings.

How to check? Unplug the refrigerator, carefully move it away from the wall and inspect the compressor (usually located at the bottom of the back). Try to shake it by hand: if there is play, tighten the fastenings or replace the shock absorbers. If the compressor housing is hot (more than 60°C) and the knocking increases during startup, immediately turn off the unit: this is a sign of a critical motor malfunction.

⚠️ Attention: Do not try to disassemble the compressor yourself! Inside there is refrigerant under pressure, and improper repairs can lead to a freon leak or a short circuit.

Disconnect the refrigerator from the mains|Check the compressor play by hand|Inspect the shock absorbers for cracks|Tighten the fastenings (if there is access)|Ring the motor windings with a multimeter (for experienced users)-->

2. Problems with the fan: knocking in No Frost models

Refrigerators with the system No Frost (Samsung RB37J5240SA, LG GA-B489YDQZ, Indesit DF 5200 W) are equipped with a fan to distribute cold air evenly. If it starts knocking, the reasons may be as follows:

• ❄️ Icing of the blades —if the defrosting system malfunctions, ice builds up on the fan and clings to the housing.
• 🔄 Foreign object —pieces of cling film, lids or ice shards get into impeller.
• 🔧 Bearing wear —over time, the lubricant dries out, and the fan shaft begins to “beat” when rotating.

To fix the problem, turn off the refrigerator, defrost it (at least 12 hours) and check the fan. It is located behind the back panel of the freezer. Gently rotate the blades by hand: if they cling to something or rotate with difficulty, they need to be cleaned or replaced. In models Samsung and LG the fan is mounted on latches, in Indesit and Atlant - on screws.

3. The impact of the refrigerant tubes on the housing

Thin copper or aluminum tubes through which freon circulates can touch with the body of the refrigerator or other parts. When the compressor is turned on, the tubes vibrate and make knocking or rattling noises. This problem is more common in refrigerators with a bottom freezer (Atlant MHM 1705, Biryusa 145) and in models with an open back wall.

How to find a problem area? Turn on the refrigerator, listen to where the sound is coming from, and gently press the tubes in that area. If the knocking stops, it means the tube is touching the body. The solution is simple: place a piece of foam rubber or rubber gasket between the tube and the body. In some cases, tying the tubes with ties helps so that they do not dangle.

⚠️ Attention: Do not use metal objects to secure the tubes! They can grind the copper surface, which will lead to freon leakage.

What to do if the tube is already damaged?

If a dent, crack or signs of corrosion are visible on the tube, immediately turn off the refrigerator and call a technician. Freon leakage not only disrupts the operation of the unit, but is also hazardous to health (if vapors are inhaled). Self-repair of tubes requires special equipment (vacuum pump, soldering torch) and certified refrigerant.

4. Malfunction of the start-up relay

The relay is a small box attached to the compressor. It is responsible for starting the motor and protecting it from overloads. If the relay fails, it starts clicking or knocking every time the compressor is turned on. In some cases, knocking is accompanied by the refrigerator turning off 5-10 seconds after starting.

Causes of relay failure:

• 🔥 Overheating —if the refrigerator is in a hot room or too close to the wall, the relay overheats and becomes deformed.
• ⚡ Power surges —with sudden changes in current, the relay contacts “stick” or burn out.
• 🕒 Natural wear —the relay has moving contacts that wear out over time.

You can check the relay with a multimeter: with the refrigerator turned off, remove the relay cover and ring the contacts. If the resistance between the terminals is zero or infinity, the relay is faulty. Replacement will cost 800–2000 rubles (depending on the model). In refrigerators Nord i Pozis the relay is often built into the compressor, so the entire unit needs to be replaced.

5. Problems with capacitor mounting

The condenser (the grill on the back wall of the refrigerator) sometimes moves away from the body and begins to vibrate, hitting other parts. This occurs due to:

• 🔨 Loose fastenings — the screws or latches holding the capacitor become loose over time.
• 🧊 Deformations grilles —the capacitor may bend if transported or cleaned carelessly.
• 🌀 Incorrect installation —if the refrigerator was not level, the condenser could move.

The solution is simple: turn off the refrigerator, unscrew the back panel and check the position of the condenser. If it is loose, tighten the fasteners or add rubber gaskets. In models Liebert i Electrolux the capacitor is often mounted on plastic clips, which break if handled carelessly. In this case, the clips will have to be replaced.

If the capacitor is deformed, it can be carefully straightened with pliers. But be careful: strong pressure can damage the tubes and cause freon leakage. After repair, check that the capacitor does not touch other metal parts - this may cause corrosion.

6. Knocking from dishes or food inside the chamber

Sometimes the cause of the knocking lies not in a breakdown, but in improper placement of objects inside the refrigerator. Cans, bottles or containers may come into contact with walls or shelves, causing vibration noises from the compressor. This happens especially often in refrigerators with air cooling system (No Frost, Frost Free, where air circulation increases vibrations.

What to check:

• 🥫 Glass jars - when the temperature changes, the glass may slightly deform and knock on metal shelves.
• 🍾 Plastic containers —if they are too close to the ventilation holes, they can be “blown in” by the air flow.
• 🧊 Ice in the freezer —large pieces of ice when during thawing, they can fall and hit the walls.

Solution: rearrange the dishes, leaving a gap of 1-2 cm between the jars and the walls. Place food in the freezer so that it does not touch the fan. If the knocking comes from ice, defrost the freezer and check the operation of the system. No Frost.

7. Malfunction of the thermostat or temperature sensors

If the refrigerator is knocking when turned on or off, the problem may be related to the thermostat or electronic sensors. These devices monitor the temperature and send signals to the compressor. If they malfunction, the compressor turns on too often or operates jerkily, which causes a knock.

Signs of a thermostat failure:

• ❄️ The refrigerator freezes too much or, conversely, does not cool.
• ⏱️ The compressor turns on every 5-10 minutes (normally - once every 30-60 minutes).
• 🔊 The knock is accompanied by relay clicks, but the motor does not start.

You can check the thermostat by turning its knob to maximum cooling: if the compressor does not turned on, the part is faulty. In electronic models (Samsung RL38, Bosch KGE39XL40), sensor malfunctions can only be diagnosed using a special tester. Replacing the thermostat will cost 1500–3000 rubles, the sensor - up to 5000 rubles.

⚠️ Attention: In electronically controlled refrigerators (LG Smart ThinQ, Samsung Family Hub), a malfunction of the sensors can block the operation of the entire unit. Do not try to reset errors with the button - this may lead to firmware failure.

8. Other possible causes of knocking

If none of the above reasons apply, pay attention to less obvious factors:

• 🏗️ Uneven floor —if the refrigerator is tilted, the vibration increases. Use a building level to check.
• 🔌 Unstable voltage - current surges cause jerks in the operation of the compressor. Install a voltage stabilizer.
• 🐭 Rodents or insects —mice can chew through the insulation of wires, and cockroaches can get into the ventilation holes.
• 🌡️ Overloading the freezer compartment —if products are stacked too tightly, this disrupts air circulation and increases the load on the fan.

In rare cases, knocking can come from faulty defrosting heating element (in models No Frost) or failure of the electronic control module (in refrigerators with a display). These faults require professional diagnostics.

FAQ: Frequently asked questions about knocking in the refrigerator

❓ The refrigerator knocks when turned on, but then works normally. Is this dangerous?

If the knocking is short-term (1-2 seconds) and is not accompanied by other symptoms (overheating, shutdowns), most likely it is normal compressor startup sound. In inverter models (LG Linear, Hitachi Inverter), the knock may be a little louder due to the characteristics of the motor. However, if the sound increases over time, check the compressor mounts and shock absorbers.

❓ Is it possible to replace the compressor shock absorbers yourself?

Yes, if you have experience working with equipment. Shock absorbers are mounted with bolts or latches. The main thing is do not overtighten the fastenersnot to deform the compressor housing. For models Atlant and Stinol universal rubber gaskets are suitable (article 2418976003), for Samsung and LG it is better to take original ones. After replacement, check that the gap between the compressor and the frame is 2-3 mm.

❓ The fan in the freezer is knocking. What to do?

First defrost the refrigerator for 12-24 hours. If the knocking noise persists:

1. Turn off the power.
2. Remove the back panel of the freezer (in most models it is secured with clips).
3. Check whether the fan blades are touching the ice or the cabinet. If so, carefully clear the ice with a plastic spatula.
4. Turn the fan by hand: if it rotates with difficulty or creaks, replace it.

In models No Frost also check the operation of the defrosting heating element (heater) - its malfunction leads to icing of the fan.

❓ The refrigerator is knocking and not freezing. What's the matter?

This is a serious symptom that may indicate:

• Freon leak - if the tubes are damaged, the compressor runs "idle", making a knocking sound.
• Compressor jamming - the motor tries to start, but cannot crank shaft.
• Thermostat malfunction —the compressor does not receive a signal to turn on.

In this case It is not recommended to turn on the refrigerator —this may aggravate the breakdown. Call a technician for diagnostics.

❓ How to reduce the noise of the refrigerator?

If the knocking is not associated with a breakdown, try these methods:

• Install the refrigerator on a flat surface (use a level).
• Place rubber pads under the legs for shock absorption.
• Move the refrigerator 5–10 cm away from the wall for better ventilation.
• Rearrange the dishes inside so that they do not touch the walls.
• Check that the power cord is not touching the back wall (vibration may transmitted over the wire).

In inverter models (Panasonic NR-BN, Toshiba GR-WF), the noise can be reduced by turning on the "Eco" or "Quiet" mode.