Why the refrigerator knocks: when is it normal, and when is it a signal of breakdown

Did your refrigerator suddenly start making suspicious knocks, clicks or a rhythmic hum? Don’t rush to panic: most sounds are normal operation of the unit. But some signals require immediate response to avoid costly repairs. In this article we will analyze all possible causes of knocking from harmless to critical, teach you to distinguish them by the nature of the sound and give step-by-step instructionswhat to do in each case.

Modern refrigerators (even models with the system No Frost) do not operate silently. The compressor, fans, refrigerant circulation - all this creates background noise. However rhythmic knocking at intervals of 10-30 seconds, accompanied by vibration of the housing, in 80% of cases indicates a malfunction of the start relay or wear of the compressor shock absorbers. If the sound appears after moving or defrosting, the problem may be due to incorrect installation. Let's take a closer look.

1. Normal refrigerator sounds: when knocking is not dangerous

Not every knock is a sign of a breakdown. Manufacturers LG, Samsung i Atlant in the instructions directly indicate that some sounds are standard. Here's what you can hear in a working unit:

• 🔊 Clicks when turning on/off —the starting relay is activated, starting the compressor. Frequency: 1-2 times per hour.
• 💨 Fan noise in models with No Frost - the sound resembles a weak hum or air flow. It intensifies when the door is open.
• 🌡️ Crackling of plastic —case parts expand/contract with temperature changes (especially noticeable in new refrigerators in the first 2-3 weeks).
• 💧 Gurgling or gurgling —circulation of refrigerant through the tubes. The sound may become louder at the first start after defrosting.

How to distinguish a normal knock from a breakdown? Pay attention to the regularity and accompanying signs:

• ✅ Safeif the sound appears rarely, is not accompanied by vibration and does not increase over time.
• ❌ Alarmingif the knocking becomes louder, the body vibrates, the refrigerator does not freeze or heat up well.

2. Knocking due to improper installation: how to fix it in 10 minutes

If the refrigerator started knocking immediately after moving, installation or repair, the problem is most likely a violation of the installation rules. Here are the most common mistakes and their consequences:

To diagnose the problem, follow vibration test:

1. Open the refrigerator door and listen: if the knocking stops, the problem is in the legs or touching the walls.
2. Try to slightly shake the refrigerator with your hands. If it wobbles, the legs are not adjusted.
3. Shine a flashlight on the back wall: the transport bolts are visible even without removing the cover.

Make sure that the legs touch the floor|Check the gaps with the walls (at least 5 cm)|Remove the transport bolts (if any)|Adjust the position according level|Check the fastening of the back cover-->

⚠️ Attention: If the refrigerator is installed on linoleum or laminate, vibration may increase due to the slippery surface. Use rubber pads under the feet or an anti-vibration mat.

3. Compressor failure: how to recognize it by sound

The compressor is the “heart” of the refrigerator, and its malfunctions are often accompanied by characteristic sounds. Dangerous symptoms:

• 🔨 A loud knock with a metallic tint —wear of the piston group or bearings. The sound intensifies during startup and may be accompanied by a hum.
• ⚡ Clicks with a pause 5-10 seconds - the compressor tries to start, but cannot (the starting relay is faulty).
• 🔥 Continuous hum with vibration —compressor overheating due to high load or refrigerant leak.

How to check the compressor yourself:

1. Unplug the refrigerator for 10 minutes, then turn it on. If after a pause the knocking repeats, the problem is in the compressor.
2. Touch the back wall below with your hand: if the case hot (more than 60°C), the compressor is overloaded.
3. Look on temperature indicator: if the refrigerator does not cool, but the compressor is humming, there may be a freon leak.

The knock of the compressor is often confused with the operation of the fan (in models No Frost). To distinguish them:

• 🌀 Fan makes a uniform noise, similar to the operation of a computer cooler. There is no knock.
• ⚙️ Compressor knocks rhythmically, with pauses, and the sound comes from below.

⚠️ Attention: If the compressor knocks and does not turn off for more than 20 minutes, turn it off immediately refrigerator from the mains! Long-term operation in this mode can lead to turn-to-turn short circuit windings and complete replacement of the unit.

What to do if the compressor is knocking, but the refrigerator is working?

Even if the refrigerator is freezing, the rhythmic knocking of the compressor is a cause for concern. This is a sign wear of shock absorbers or loose fastenings. Over time, vibration can damage refrigerant lines or electronics. We recommend:

1. Check the compressor fastening (it must be firmly fixed to the frame).
2. Replace rubber shock absorbers (parts cost from 300 rubles).
3. If the knocking is accompanied foreign odor - call a technician to diagnose an oil leak.

4. Start relay: why it clicks and knocks when starting

The start relay is a small box next to the compressor, which starts the engine protects it from overloads. Its malfunctions manifest themselves as follows:

• 🔄 Cyclic clicks with an interval of 5-15 seconds - the relay tries to start the compressor, but cannot (the spiral is burned out or the contacts are stuck).
• 💥 Single loud click when turned on - break in the relay winding.
• 🔌 Knock with sparking (visible when the light is off) - short circuit in the contacts.

How to check the relay at home:

1. Disconnect the refrigerator from the mains.
2. Remove the protective cover from the compressor (usually it is plastic, secured with latches).
3. Carefully remove the relay (it is connected to compressor 2-3 wires).
4. Shake the part: if something rattles inside, the relay is faulty.

The cost of a new relay is from 500 to 2000 rubles depending on the model of the refrigerator. Replacement takes 10-15 minutes and does not require special tools. Important: check the compressor before installing a new relay —if it is burnt out, replacing the relay will not help.

5. Fan No Frost: why it rattles and how to fix

Refrigerators with a system No Frost (for example, Samsung RB-30 J3200 or Bosch KGE39XW2AR) are equipped with a fan for uniform distribution of cold. Its breakdowns manifest themselves as follows:

• 🌀 Continuous hum with periodic clicks —the fan blades cling to ice or a foreign object.
• 🔊 Screeching or squealing —wear of the motor bearing.
• 🛑 The fan does not spin, but the refrigerator is working—power failure or motor malfunction.

How fix the fan yourself:

1. Unplug the refrigerator and defrost it for 12-24 hours (ice can block the blades).
2. Remove the back panel in the freezer (usually attached with self-tapping screws).
3. Check whether a foreign object has gotten inside (pieces of food, packaging).
4. Turn the blades by hand: if they rotate with difficulty, lubricate the bearing with silicone grease.

If the fan does not start even after defrosting, check:

• 🔌 Power - inspect the wires for breaks.
• 🛠️ Engine — when voltage is applied, it should vibrate slightly.
• 🌡️ Defrost sensor —if it is broken, the fan may not turn on due to icing.

⚠️ Attention: Do not try to disassemble the fan motor without experience! In models LG and Samsung the motors are often non-separable, and attempting repairs can lead to complete failure.

6. Rattling of tubes and housing parts: how to eliminate

Sometimes knocking occurs not because of a breakdown, but because vibration of partsHere are the most common sources of noise:

• 🔧 Refrigerant pipes - if they touch the back wall or compressor, they will rattle during operation.
• 🧲 Magnetic door seal - dry out over time and may come off with a characteristic click.
• 📦 Shelves or containers —if they are loose, they will rattle when vibrated.
• 🔩 Compressor mounts —loose bolts lead to increased vibration.

How to eliminate rattling:

1. Open the refrigerator and press the shelves one by one - if the sound stops, fix them more tightly.
2. Check the seal: if it comes off, lubricate it silicone grease or glue with double-sided tape.
3. Carefully bend the tubes that touch the body (use a plastic spatula to avoid damage).
4. Tighten the compressor fastenings (you will need a 10 or 12 mm).

If rattling appeared after transportationcheck:

• 📦 Are the internal shelves secured (they could have moved during transportation).
• 🧲 Integrity of the magnetic seal (if damaged, it must be replaced).
• 🔧 Position of the capacitor (metal grille at the back) - it should not touch the walls.

7. When to call a specialist: 5 critical symptoms

Some. breakdowns cannot be repaired independently. Immediately turn off the refrigerator and call a specialistif:

• ⚡ The knocking is accompanied by sparking or there is a burning smell - an electrical short circuit.
• ❄️ The refrigerator does not freeze, but the compressor works without stopping - freon leak.
• 🔥 The body heats up to 70°C and above - the compressor is overheating or the windings are shorted.
• 💦 There is a puddle of oil under the refrigerator —depressurization of the compressor.
• 🛠️ After replacing the relay, the knocking does not go away —the compressor or electronics are faulty.

The cost of repairs depends on breakdowns:

Before agreeing to repairs, check:

• 🔧 Warranty for work (at least 6 months).
• 💰 Cost of diagnostics (in some services it is free when ordering repairs).
• 📋 Are original spare parts used (especially important for Liebert, Electrolux, Bosh).

⚠️ Attention: Refrigerator parts may differ even within the same model (for example, Atlant MXM-1708 2020 and 2023 releases). Always check serial number (located on the sticker inside the chamber or on the back) before purchasing spare parts.

FAQ: Frequently asked questions about knocking in the refrigerator

🔊 The refrigerator knocks only at night - why?

At night knocking may intensify due to:

• 🌙 Lower room temperature - the compressor works more intensely.
• 🏠 Silence - during the day the noise is masked by household sounds.
• 🔌 Power surges (if the knocking coincides with the operation of other devices).

Solution: check voltage stabilizer and adjust the legs of the refrigerator.

⚡ A knocking sound appeared after the lights were turned off - what to do?

After a power surge, the starting relay or varistor (protective element) could burn out.

1. Turn off the refrigerator for 30 minutes, then turn it on again.
2. If the knocking noise repeats, check the relay (see section 4).
3. Install surge filter to protect against jumps.

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

Yes, this is one of the simplest procedures:

1. Turn off the refrigerator and remove the back cover.
2. Unscrew the compressor fastenings (usually 4 bolts).
3. Remove the old shock absorbers (rubber cushions) and install new ones.
4. Secure the compressor and check the vibration.

The cost of shock absorbers is from 200 rubles per set.

🔧 The refrigerator is knocking and does not freeze - what is the reason?

Probable breakdowns:

• 🔥 Compressor burned out (need replacement).
• ❄️ Freon leak (refilling required).
• 🛑 Fan jammed (in models No Frost).
• 🌡️ Thermostat is broken (does not give a signal to turn on).

Call a technician urgently - without refrigeration, food will spoil in 6-12 hours.

📅 How often should you service the refrigerator to avoid knocking?

Preventive measures:

• 🧹 Defrosting - 1-2 times a year (even for No Frost).
• 🧲 Cleaning the seal - once a month (with soap solution).
• 🔧 Checking the fasteners - once every six months (tighten the legs, compressor).
• 💨 Cleaning the condenser - once a year (with a vacuum cleaner or brush).