The situation when the refrigerator makes a characteristic hum, but does not get cold inside, and the food begins to deteriorate, causes panic in any home cook. The sound of a running engine creates the illusion that the equipment is working properly, but the absence of cold indicates a serious malfunction in the refrigerant circulation system or electrical circuit. In this case, compressor may be started, but not perform its main function - to compress the gas to remove heat.
Often, equipment owners ignore the first signs of a malfunction, relying on the fact that the unit will “defrost” by itself. However, if inverter or a conventional motor hums in vain, this can lead to its complete combustion in a matter of hours. It is important to understand that a hum without cooling is not the norm, but a symptom that requires immediate intervention.
In this article we will analyze in detail the mechanical and electrical reasons for this behavior of a household appliance. You will learn how to carry out initial diagnostics, which parts most often fail and in which cases calling a technician is the only solution. The critical point is the idle time of the motor: if it hums for more than 20 minutes without cooling, it should be de-energized to avoid a wedge.
Principle of operation: why the hum is heard
To understand the nature of the malfunction, it is necessary to briefly consider the design of the refrigeration circuit. The main node that creates noise is compressor. This is an electromechanical pump that circulates refrigerant (freon) through a system of tubes. During normal operation, it compresses the freon gas, increasing its pressure and temperature, after which the gas is sent to the condenser to cool.
The hum you hear is the vibration of the piston group and electric motor inside the sealed casing. If the refrigerator stops freezing, but the sound of the motor remains, this means that the electrical circuit is closed and current is supplied to the motor windings. However, the mechanical part or the thermodynamic cycle is broken.
⚠️ Attention: The constant hum of a running compressor in the absence of cold indicates that the system is operating in emergency mode. This leads to overheating of the windings and can cause a fire hazard.
There are two main scenarios for the development of events. In the first case, the motor runs smoothly, but there is no cold - this often indicates a gas leak or capillary blockage. In the second, an intermittent buzzing sound with clicks is heard, after which there is silence. This indicates problems with starting the engine or mechanical jamming.
Modern models with No Frost may hum due to a fan malfunction, even if the compressor is turned off. It is important to be able to distinguish the source of the sound: low-frequency hum comes from below (from the motor), and high-frequency noise or crackling comes from inside the chamber (from the fan).
Freon leak: the most common reason
The most common reason why the refrigerator hums but does not cool is a banal refrigerant leak. Freon circulates in a closed loop, but over time, microcracks may form in the places where the tubes are soldered or in the evaporator. The gas evaporates, and a vacuum or insufficient pressure remains in the system for effective heat exchange.
The compressor, sensing the lack of pressure, tries to compensate for this and works in increased mode, almost without interruption. This is why it seems that the equipment is working “like a clock,” but the temperature inside is rising. It is almost impossible to detect a leak visually, since freon has neither color nor odor.
Indirect signs of a leak are:
- 🌡️ The motor is hot to the touch, and the condenser (grid at the back) remains cold or barely warm.
- ⏱️ The refrigerator operates continuously without going on vacation (the cycle is not interrupted).
- ❄️ A “fur coat” appears in the freezer only at the entrance or there is no ice at all, although it used to be there.
To restore functionality, you will need to call a technician with equipment to find leaks (leak detector), evacuate the system and refill with new freon. It is impossible to fix this problem without special tools Is it possible to refuel the refrigerator yourself?.
Is it possible to refill the refrigerator yourself?
Refilling it yourself is dangerous and ineffective. Without a vacuum pump, moisture will remain in the system, which will turn into an ice plug and cause the compressor to fail within a week. An accurate calculation of the weight of the refrigerant is also required, an error of 10 grams is critical.
Malfunction of the starting relay
If you hear the refrigerator humming for 5-10 seconds, then there is a loud click and the motor stops, and after a while the cycle repeats, the problem lies in the starting relay. This device is responsible for supplying voltage to the starting winding of the compressor at the moment of start.
Inside the relay there is a coil or posistor, which wear out over time. When the relay fails to start the motor rotor, the current in the windings increases sharply, the thermal protection is activated, and a shutdown occurs (clicking). The motor cools down, the protection is reset, and the start attempt is repeated.
Diagnosis of this breakdown is quite simple and can often be done by a home handyman:
- Unplug the refrigerator.
- Get to the compressor at the back of the unit.
- Remove the plastic casing and disconnect the relay with wires.
- Shake the relay: if you hear a knock inside (like a bolt in a jar), it means the contacts are damaged and the part requires replacement.
Replacing the start relay is one of the cheapest and fastest repair procedures. It is important to select a part with a similar marking, since the current parameters may differ for different compressor models. Using an unsuitable relay can lead to burnout of the motor windings.
Clogged capillary tube
Another technical reason why the refrigerator hums, but not freezes, the capillary tube is clogged. This is the thinnest copper channel through which freon is supplied to the evaporator. During operation, moisture, oil oxidation products, or small debris may accumulate in the system.
The resulting ice or oil plug blocks gas circulation. The compressor begins to pump freon into the closed volume, creating excess pressure in front of the plug and a vacuum after it. The engine is overloaded, trying to push gas, which is accompanied by a characteristic hum.
The blockage can be diagnosed by the following signs:
- 🧊 The freezer may work normally, but it is warm in the main chamber (or vice versa, depending on the location of the blockage).
- 🔥 The condenser at the back heats up only partially (to the point of the plug).
- 🔊 The sound of the compressor becomes more strained and louder than usual.
Removing the blockage requires professional cleaning of the system with high-pressure nitrogen and subsequent refilling. Sometimes it is necessary to replace the filter-drier, which is designed to capture moisture, but over time it overflows.
Mechanical wear or compressor wedge
The most unpleasant scenario is the failure of the very heart of the refrigerator. If the motor hums very loudly, with a metallic clang or a strong hum, and at the same time vibrates strongly, the piston group or bearings may have worn out.
In the worst case, it happens compressor wedge. The engine shaft is jammed and it cannot turn. Electronics or relays try to start it by supplying current, the shaft only hums with voltage, but does not move. Thermal protection turns off the unit, but after cooling the cycle repeats.
Main symptoms of mechanical failure:
- ⚙️ The hum is accompanied by strong vibration of the housing.
- 🔥 Compressor heats up to very high temperatures in a short time.
- 🔌 When trying to start, the machine in the panel immediately knocks out (short circuit in the windings).
The compressor is not repaired at home. They either replace it with a new one, or (in rare cases) try to “unwedge” it by applying high voltage, but this only gives a temporary effect. If your refrigerator is more than 10 years old, replacing the compressor is often not economically feasible.
☑️ Diagnostics before calling a technician
Comparative table of faults
For ease of diagnosis, we will summarize the main symptoms in a single table. This will help you quickly navigate the nature of the breakdown before the specialist arrives.
| Symptom | Probable cause | Character of sound | Difficulty of repair |
|---|---|---|---|
| Humming, not freezing, cold condenser | Freon leak | Smooth, continuous | Medium (needs refilling) |
| Buzzing for 5-10 seconds, clicking, silence | Faulty starting relay | Intermittent buzzing + clicking | Low (part replacement) |
| Humming, vibrating, not cooling | Compressor wedge | Loud, metallic | High (motor replacement) |
| Humming, slightly freezing, the capacitor is partially heated | Clogged capillary | Tight, even | Medium (cleaning) |
As can be seen from the table, the nature of the sound and the behavior of adjacent nodes provide a clear direction for troubleshooting. However, the final diagnosis must be made by a master with a manometric manifold.
The influence of the No Frost mode and electronics
In modern models with the system No Frost another source of noise and potential problems is added - the fan. If the refrigerator hums, but does not freeze, the cause may be icing of the evaporator due to a malfunction of the defrost system.
Ice freezes on the evaporator, blocks the air supply channels, and the fan begins to hum, trying to drive air through the ice crust, or its blades touch the ice. In this case, the compressor can work normally, but the cold does not enter the chamber.
⚠️ Attention: Do not try to pick out the ice with a knife or sharp objects. Damage to the evaporator will lead to an immediate leak of freon and expensive repairs.
It is also worth mentioning the role of the electronic control module. If the refrigerator's "brains" are faulty, they may not command the compressor to turn on, although the unit itself may produce background sounds from transformers or relays. But more often than not, when the electronics break down, the refrigerator simply remains silent.
For a compressor it can last up to 10 years, while for electronic components it can last only 1 year. Before paying for repairs, check the documents for the equipment.
Frequently asked questions (FAQ)
Why does the refrigerator hum after defrosting, but does not freeze?
If you defrosted the refrigerator less than 8-10 hours ago, it might not have time to freeze temperature. If more than a day has passed and there is no cold, you may have damaged the tubes during defrosting or moisture got into the system, causing a blockage. The electronics could also burn out due to a power surge when turned on.
Is it possible to operate a humming refrigerator?
It is strictly not recommended. If the compressor hums without cooling, it overheats and can burn out in a few hours. If the relay buzzes, this leads to voltage surges in the network. It is better to turn off the device until the reasons are found out.
How much does it cost to repair if the refrigerator is humming and not cooling?
The cost depends on the unit. Replacing the relay is the cheapest operation. Refilling with freon costs more. Replacing a compressor is the most expensive procedure, often accounting for 50-70% of the cost of a new refrigerator.
How to extend the life of a compressor?
Do not place the refrigerator close to the wall (you need a gap for ventilation), defrost regularly (if there is no No Frost), do not load hot foods into the chamber and keep the condenser at the back clean unit.