The situation when the refrigerator compressor works without interruption, and the unit itself hums for days on end, is familiar to many owners of household appliances. This is not just an annoying noise that disturbs sleep or watching TV in the next room, but also an alarming signal that the cooling system is operating in emergency mode. If the motor does not turn off, it experiences enormous overloads, which inevitably leads to rapid wear of mechanical parts and, ultimately, to expensive repairs or complete replacement of the unit.
Modern models of refrigerators, be it classic Indesit, reliable Bosch or technological Samsung with the system No Frost, are equipped with complex electronics, which must control the on and off cycles. However, even the most advanced technology can fail. Understanding why the compressor hums continuously will help you quickly navigate the problem and make the right decision - try to fix the problem yourself or call a technician.
In this article we will look in detail at the main reasons why the refrigerator stopped turning off. We will touch on both trivial operating errors and serious technical malfunctions that require the intervention of professionals. It is important not to ignore the first symptoms, because timely diagnosis can save your refrigerator from a “coma” when it is no longer possible to revive it.
1. Violation of the seal of the chamber and wear of the seal
One of the most common and commonplace reasons for the continuous operation of the compressor is the ingress of warm air into the refrigeration or freezer chamber. The cooling system is designed in such a way that it strives to maintain a given temperature. If the seal is broken, heat constantly flows inside, sensors detect an increase in temperature, and the motor-compressor continues to work, trying to “catch up” with cold.
The main culprit here is often the rubber seal located around the perimeter of the door. Over time, rubber loses its elasticity, cracks, deforms, or simply becomes overgrown with a coating that prevents a tight fit. Even a microscopic gap leads to the fact that cold air evaporates, and warm air is sucked inside. As a result, the refrigerator works around the clock, trying to compensate for the heat gain.
To check the tightness, you can use a simple method with a sheet of paper or a bill. Clamp the sheet between the body and the seal around the entire perimeter of the closed door. If the paper falls out or is easily pulled out without resistance, the seal is broken. Also visually inspect the rubber for cracks, dents or dirt.
⚠️ Attention: If the seal is simply dirty, it can be gently washed with warm water and a mild detergent. However, if the rubber is cracked or has lost its shape, cleaning will not help - you will need to completely replace the sealing cuff.
In addition, check whether it interferes with closing doors, dishes standing on shelves at the very edge, or an adhered layer of ice at the end of the chamber. Sometimes it is enough just to adjust the plate for the compressor to start working normally.
2. Malfunction of the thermostat or temperature sensor
The thermostat (thermostat) is the “brain” that commands the compressor to turn on when the chamber becomes warm, and turn off when the temperature reaches normal. If this device fails, it may send incorrect signals. In particular, if the contacts are broken or the relay is stuck, the thermostat can constantly “think” that it is warm in the refrigerator and not interrupt the motor power supply circuit.
In models with electronic control, the role of a thermostat is performed by air temperature sensors. Their readings may be distorted due to oxidation of contacts, damaged wiring, or software failures in the control module. If the sensor “lies”, showing, for example, +10°C instead of the real +4°C, the compressor will work non-stop, trying to cool the chamber to impossible values.
Diagnostics of the thermostat often requires special instruments, but the initial check can be carried out visually and by ear. If, when turning the thermostat knob (in mechanical models), a characteristic click does not occur, and the compressor continues to hum, the problem is most likely in the regulator.
How to check a thermostat with a multimeter?
To check a mechanical thermostat, you need to remove it and “ring” the contacts with a multimeter in ohmmeter mode. At room temperature the contacts should be closed. If you place the thermostat sensing element in the freezer, the contacts should open. If this does not happen, the device is faulty.
Replacing the thermostat is a procedure that can be performed independently if you have basic skills, but requires caution. It is important to choose an analogue with exactly the same parameters, otherwise the refrigerator will either turn on frequently or, conversely, not freeze enough.
3. Refrigerant (freon) leak
Freon leak is a serious technical malfunction that often leads to the compressor running without interruption. The principle is simple: there is less refrigerant in the system; there is not enough of it to reach the required temperature in the evaporator in a standard time. The sensors record that the set mode has not been achieved and do not give a command to turn off the motor.
The compressor in this situation works to wear out, trying to compensate for the lack of freon with increased productivity. This leads to severe overheating of the engine (especially in models LG and Whirlpool with inverter motors) and can cause its rapid failure. An indirect sign of a leak is often insufficient cooling of products with a continuous hum of the unit.
Where can a leak form? Most often these are:
- 🔧 Places for soldering tubes (welded seams can microcrack over time).
- 🔧 Evaporator (especially in models with a “crying” wall, where the tubes are mounted in the back wall).
- 🔧 Condenser (grid at the back refrigerator) if it has been subjected to mechanical damage or corrosion.
- 🔧 Compressor rod (shaft exit point).
It is almost impossible to independently find the location of the leak and fill the refrigerator with freon without specialized equipment (leak detector, vacuum pump, pressure gauge station). Attempts to simply add gas without eliminating the hole will only give a temporary effect.
⚠️ Attention: Freon is not just a gas, it is a working fluid circulating under pressure. If you hear hissing or see oily stains on the pipes at the back of the refrigerator, immediately unplug the appliance and call a service technician. Further operation is dangerous.
4. Problems with the No Frost system and defrost
In refrigerators with a system No Frost continuous operation of the compressor is often associated with a malfunction of the defrost system. In such units, frost constantly forms on the evaporator (which is hidden behind a plastic panel inside the freezer). The defrost heating element must be turned on periodically to melt this ice. If the defrosting system does not work, the evaporator becomes overgrown with a thick “coat” of ice.
Ice is an excellent heat insulator. When the evaporator is completely covered with ice, it stops effectively cooling the air that circulates through the chamber. The fan blows warm air, the sensors record the high temperature, and the compressor works non-stop, trying to break through the ice crust. At the same time, there may be heat in the chamber itself, and behind the panel there is an ice monolith.
The main elements of the defrost system that may fail:
- ❄️ Defrost heating element (the heating element could burn out).
- ❄️ Defrost sensor (defrost timer) - does not give a command to turn on the heating.
- ❄️ Thermal relay - protects the heating element from overheating, but can “stick” when open.
- ❄️ A blown fuse in the defrost circuit.
For diagnostics it is often required defrost the refrigerator manually within 10-12 hours. If, after complete defrosting and turning on, the unit starts to work normally (turns on and off), but after 1-2 weeks the situation repeats, the problem is guaranteed to be in the defrosting system.
☑️ Symptoms of a malfunction of the No Frost system
5. Stuck start relay or compressor malfunction
Sometimes the reason lies in the very “heart” of the refrigerator - the compressor or start relay, which helps it start. The start relay is a small mechanism that supplies an impulse to the motor winding. If the relay contacts burn or stick, it may not open the starting winding circuit, which is why the compressor hums but does not start, or operates in emergency mode.
A more serious problem is an interturn short circuit in the windings of the compressor itself. In this case, the engine loses power, cannot develop the required pressure and reach the shutdown temperature. It works constantly, gets very hot (up to 80-90°C and above), and the refrigerator freezes slightly.
Comparison of symptoms of relay and compressor malfunction:
| Symptom | Faulty start relay | Compressor is faulty |
|---|---|---|
| Sound at startup | Click, hum for 5-10 seconds, then click and silence | There is a hum, but it can be quiet or intermittent |
| Case heating | The main relay gets hot | The motor housing itself gets very hot |
| Operation | Start attempts every few minutes | Continuous operation or complete failure |
| Repair | Replacement of the relay (cheap and fast) | Replacement of the compressor (expensive and difficult) |
If you notice that the compressor is hot, and the refrigerator does not freeze, and the motor runs continuously, most likely its resource exhausted. Replacing a compressor is a complex procedure that requires evacuation of the system and refilling with freon, which is performed only in service centers.
6. Influence of external factors and operating mode
Continuous operation of the compressor does not always mean a breakdown. Often we ourselves create conditions in which the refrigerator is forced to work in increased mode. For example, placing a refrigerator near a radiator, stove, or in direct sunlight causes the cooling system to work harder to remove heat.
It is also important to consider the room temperature. Most refrigerators are designed to operate in the temperature range from +10°C to +32°C (climate class SN, N, ST). If the room is unheated in winter and the temperature drops below +10°C, the oil in the compressor thickens and it may not work correctly. If in the summer the kitchen is +35°C or higher, the condenser will not have time to cool down, and the compressor will work almost without interruption.
Another factor is loading with warm products. If you put freshly cooked hot soup or a bucket of vegetables just brought from the market into the chamber, the compressor will work until it cools the entire volume to the set temperature. This is normal mode, but it should not last for days.
Also check the temperature settings. If you accidentally set the Super Freeze mode (usually indicated by a snowflake or button Super Freeze), the compressor will run constantly, ignoring the thermostat readings, until you turn off this function manually or the timer expires (usually 24-48 hours).
Frequently asked questions and answers (FAQ)
How long should a compressor operate normally?
In normal operation, the compressor operating time ratio ranges from 30% to 50%. This means that out of one hour he works for 20-30 minutes, and rests the rest of the time. In hot weather or when fully loaded, this figure can reach 60-70%, but working non-stop for days is always a sign of a malfunction.
Is it dangerous if the refrigerator hums constantly?
Yes, it is dangerous. First of all, for the refrigerator itself: the motor overheats, the insulation of the windings melts, the oil dries out, which leads to the compressor wedge. Secondly, there is a risk of fire due to overheating of the electrical wiring or the motor itself. Thirdly, this is damage to products, since during continuous operation without defrosting cycles or if freon leaks, the temperature in the chamber may be higher than normal.
Can continuous operation be caused by a software failure?
Yes, in modern models with electronic control (for example, Bosch, Siemens, LG) it is possible “glitch” of the control board. In this case, the processor does not receive a signal that the temperature has been reached or does not issue a shutdown command. A complete reboot can help: unplug the refrigerator for 15-20 minutes, then turn it on again. If the error was a one-time one, the operating mode will be restored.
What to do if the compressor is hot and does not turn off?
Immediately disconnect the refrigerator from the power supply! Let it sit unplugged for a few hours to allow the motor to cool down. Check if the quick freeze button is stuck, if the condenser at the back is clean, if the door closes tightly. If after switching on the situation repeats within 24 hours, call a technician to diagnose the gas system or electrical system.
Why does a new refrigerator work constantly?
When turned on for the first time, a new refrigerator takes a long time (sometimes up to 24 hours) to cool the empty chambers to the set temperature. During this period, the compressor can work without interruption - this is normal. This can also happen if you loaded a lot of food into the new refrigerator at once. Let the equipment run idle for several hours before loading.