Something in the refrigerator is knocking in the back wall: reasons and solutions

Have you noticed that the refrigerator has begun to make rhythmic knocking or clicking noises from the back? This noise can be alarming, especially if the unit previously operated silently. In fact knock on the back wall of the refrigerator is a common problem, and in 80% of cases it is not associated with a serious breakdown. But you shouldn’t ignore sounds either: they can signal a malfunction of the compressor, fan, or even a refrigerant leak.

In this article we will analyze all possible causes of knocking —from harmless (for example, vibration of pipes) to critical (breakage of the start relay). You will learn how to diagnose the problem yourself, when you can get by with adjusting the legs, and when urgent repairs are required. We also collected unique data on refrigerator models produced in 2020–2026in which knocking on the rear wall occurs most often.

1. Why the refrigerator knocks from the back: main reasons

A knock at the back of the refrigerator is usually caused by the operation of mechanical components. Let's look at the most likely sources of noise:

• 🔧 Compressor vibration —the most common cause. The compressor is attached to the frame with springs, and when starting/stopping it can knock on the housing.
• ⚙️ Start relay - clicks when the engine is turned on. Normally, the sound is single, but when the relay wears out, it knocks constantly.
• 🌀 Condenser fan - if the blades touch ice or dust, a rhythmic knock appears.
• 🧊 Refrigerant pipes - when expansion/contraction may touch the rear wall (typical for models with No Frost).
• ⚡ Solenoid valve - in refrigerators with a system Total No Frost the valve switches the refrigerant flows, making clicks.

In recent years, knocking is often associated with refrigerators. LG, Samsung and Atlant In recent years, knocking is often associated with inverter compressorsThey regulate power smoothly, but when switching modes they can make clicking noises. This is not a breakdown, but a design feature - if the knocking is not accompanied by overheating or cooling failure, there is no need to worry.

2. How to distinguish a normal knock from a breakdown

Not every knock requires repair. is heard only when not dangerous:

• ✅ The knock is heard only when starting or stopping the compressor (1-2 clicks).
• ✅ The sound is rhythmic, but is not accompanied by case overheating or cooling failure.
• ✅ The knock appeared after rearranging the refrigerator (the tubes may have shifted).

And now alarming signalsfor which diagnostics are needed:

If the refrigerator Samsung RB30J3000WW or LG GA-B489YDQL knocking when first turned on after defrosting, this is normal. In these models, the system No Frost pumps refrigerant with a characteristic sound when starting up. But if the knocking does not stop after 1-2 hours, check initial position of the tubes behind the back wall - they could have moved.

3. knocking: step-by-step instructions

To accurately determine the source of the knocking, follow these steps:

Unplug the refrigerator|Inspect the back wall for displaced tubes|Check the compressor fastening (the bolts should not be loose)|Turn on the refrigerator and listen: is there a knocking noise at startup or during operation?|Check the temperature condenser (it should not be cold when the compressor is running) -->

If a knock is heard when starting the compressor, most likely the problem is:

• 🔌 Start relay —it clicks, but the motor does not start (need replacement).
• 🔊 Compressor shock absorbers —metallic knock, sounds to the floor (requires tightening or replacement of gaskets).

If there is a knock rhythmic and constant, check:

• 🌀 Condenser fan — could be clogged with dust or ice (needs cleaning).
• 🧲 The solenoid valve — in models with Total No Frost The valve may knock when switching modes.

U Indesit and Ariston refrigerators knocks frequently thermostat —this is normal for mechanical models. But if the sound has become louder, perhaps the thermostat contacts. burnt. In this case, the part needs to be replaced (cost ~1200–2000 ₽).

How to check the start relay without tools?

Turn off the refrigerator, remove the back cover (if there is one). Find the starting relay - this is a small box on the compressor. Gently shake it: if something rattles inside, the relay is faulty and requires replacement. Do not open the relay yourself - this can lead to electric shock!

4. How to eliminate the knocking yourself

If the cause of the knocking is not is critical, you can fix it without calling a technician. Here's what to do:

🔧 Adjusting the legs and level of the refrigerator

The uneven position of the refrigerator increases the vibration of the compressor. Use a building level to level the unit. Tighten the legs so that the refrigerator tilts slightly back 1–2°) - this will reduce vibration and improve door closing.

🌀 Cleaning the condenser fan

In refrigerators with No Frost the fan may touch ice or dust To clean. it:

1. Disconnect the refrigerator from the mains.
2. Remove the back panel (if it is removable).
3. Remove dust from the fan blades with a brush or vacuum cleaner.
4. Check whether the fan is touching the ice on the evaporator (if any ice - defrost the refrigerator).

⚙️ Tightening the compressor fastenings

If the knock is metallic and radiates to the floor, check the compressor bolts. They may have loosened over time. Carefully tighten them with a wrench (do not overtighten them!). the compressor is mounted on rubber shock absorbers - if they are worn out, they need to be replaced.Atlant, Biryusa) the compressor is mounted on rubber shock absorbers - if they are worn out, they need to be replaced.

5. When to call a specialist: 5 critical cases. data-i="155">Some breakdowns require professional intervention. Immediately turn off the refrigerator and call a technician if:

Some breakdowns require professional intervention. Immediately turn off the refrigerator and call a technician if:

⚠️ Attention: If the refrigerator is knocking and at the same time the housing gets very hot (more than 50°C), this is a sign seized compressor. Continuing operation may lead to a fire!

• 🔥 A knocking sound is accompanied burnt smell —possibly burnt out compressor winding.
• ❄️ Refrigerator does not cool, but knocks constantly - freon leak or compressor breakdown.
• ⚡ After knocking, the refrigerator knocks out the machine in the panel - short circuit in the start relay.
• 💧 There is a puddle under the refrigerator, and at the same time knocking rhythmic - possible oil leakage from the compressor.
• 🔊 The knocking began louder over time - wear of the compressor bearings (replacement required).

The cost of repairs depends from breakdown:

• Replacement of the start relay: 1500–2500 ₽ (with work).
• Compressor repair: 5000–12000 ₽ (depending on the model).
• Leakage elimination freon: With inverter compressors, knocking can be a sign. In this case, the technician reflashes the control unit (cost ~2000–3500 ₽). 3000–6000 ₽.

U Liebherr refrigerators And Bosh with inverter compressors, knocking can be a sign firmware failure. In this case, the technician reflashes the control unit (cost ~2000–3500 RUR).

6. Prevention: how to prevent knocking in the refrigerator

To make the refrigerator run quieter, follow these tips:

• 🧹 Clean the condenser (grid on the back) from dust once every 6 months - this reduces the load on the compressor.
• ❄️ Defrost the refrigerator at ice appears on the back wall (even if the model is with No Frost).
• 🔌 Use a surge protector -voltage surges can damage the start relay.
• 📏 Maintain clearances when installing: at least 5 cm from the wall for air circulation.

For refrigerators with the No Frost system (for example, Samsung RL38T6000SA or LG GB-B459SLQZ) is important do not overload the freezerIf products block the ventilation holes, the fan is overloaded and may start to work. knock.

Also avoid frequent on/off the refrigerator - this reduces the life of the compressor and start relay If the lights are often turned off in your area, install uninterruptible power supply (UPS) for the refrigerator.

7. Frequently asked questions about knocking in the refrigerator

❓ Why does a new refrigerator knock when first turned on?

In the first hours of operation, knocking may be associated with by pumping the refrigerant this is normal for models. s No Frost (for example, Bosch KGE39XW2AR or Electrolux ERN1200FOX). If the knocking does not disappear after a day, check the fastening of the tubes - they may have moved during transportation.

❓ You can Is it possible to replace the starting relay yourself?

Theoretically, yes, but only with full confidence in your skills. The relay is located on the compressor and is connected to high voltage. An error during replacement can lead to electric shock or damage to the compressor. Indesit and Ariston universal relays are suitable RBM-1S or DANFOSS 103N0022.

❓ The refrigerator is knocking Atlant —what to do?

U Atlant refrigerators (for example, MHM 2835-90) knocking is often associated with by loosening the compressor or wear of the shock absorbers Try tightening the bolts with a 10mm wrench. If the knocking persists, check starting relay —in these models it fails more often than in refrigerators of other brands.

❓ Why does the knocking get louder at night?

At night the apartment is quieter, so the knocking seems louder. But if the sound actually gets louder, there are two possible reasons:

1. The compressor is running on maximum power due to increased temperature in the room (for example, if the kitchen is not ventilated).
2. Power surges in the network (at night the voltage may drop, which makes it difficult to start the compressor).

Solution: install voltage stabilizer and check the ventilation of the room.

❓ Is the refrigerator knocking after defrosting - is this normal?

Yes, in the first 1-2 hours after defrosting, knocking can be associated with:

• 🧊 Redistribution of refrigerant in the system.
• 🌀 Starting the fan (if the model is with No Frost).
• ⚙️ Adaptation compressor to a new load.

If the knocking does not stop after 3-4 hours, check initial position of the tubes they could have moved during washing.