The situation when the refrigerator is humming, the light inside is on, and food begins to spoil due to lack of cold is one of the most common and alarming for the owner of household appliances. Compressor can work non-stop, creating the illusion that the unit is working properly, but the cooling capacity in the chambers is completely missing. This indicates that the refrigerant circulation cycle is disrupted at some stage, or the control system has stopped sending correct signals for cooling.
Before calling a technician or disassembling the unit, it is necessary to conduct a primary diagnosis, which often allows you to localize the problem without deep intervention. In most cases, the reason lies either in freon leak, or in a malfunction of the sensors, or in a banal blockage of the system. Understanding the principle of operation will help you more accurately describe the problem to a specialist or, perhaps, fix the problem yourself if it is simple.
If you notice that condenser grid on the back wall remains cold or barely warm, while the motor is hot, this is a sure sign that heat exchange is not happening. Further operation in this condition will only aggravate the situation, requiring more expensive repairs.
⚠️ Attention: If you smell burning or see sparking in the compressor area, immediately disconnect the device from the power supply. Further diagnostics are possible only after the unit has completely cooled down.
Checking the thermostat and temperature sensors
One of the first reasons why refrigerator stopped freezing when the engine is running is the failure of the thermostat. This element is responsible for closing and opening the compressor power supply circuit depending on the temperature inside the chamber. If the contacts are oxidized or the mechanism is stuck in the "open" position, the motor may hum (if the circuit is bypassed), but no cold will be generated, or vice versa - the unit will work endlessly, but ineffectively.
In modern models with a system No Frost and electronic control, the role of a mechanical regulator is performed by air sensors Their readings are read by the control module, which makes the decision to start the compressor. If the sensor “lies” and tells the board that the chamber is already -20°C, although it is +10°C, the command for cooling simply will not be received. Diagnostics of such elements requires the use of a multimeter to check the resistance.
To check a mechanical thermostat, the exclusion method is often used: the contacts at the input and output are closed directly. If after this manipulation the refrigerator begins to freeze, then the problem is in the regulator. However, this method is only suitable for a temporary check, since leaving the equipment to work without temperature control It is absolutely forbidden this will lead to freezing of food and icing of the evaporator.
Replacing the thermostat is a relatively simple procedure, but requires care. The capillary tube of the new sensor must be positioned in exactly the same way as the old one was installed, otherwise the operating cycle will be disrupted. In electronic models, replacing the sensor often requires disassembling the internal panel and reflashing or resetting errors in the diagnostic menu.
Refrigerant leak: symptoms and search
The most common technical reason for the lack of cold is banal freon leak. The refrigerant circulates in a closed circuit, and if a microcrack appears in the system, the gas gradually evaporates. The compressor continues to work, trying to pump what is left, but the pressure is no longer enough for effective heat exchange. Visually, this is manifested in the fact that the condenser (grid at the back) remains cold or warm only at the very beginning.
Sometimes the leak is accompanied by the appearance of oily spots under the refrigerator or on the floor behind it. Oil flows out along with gas from the damaged tube. If you find such traces, the probability that the problem is the depressurization of the circuit is 90%. Finding a leak on your own without special equipment (a leak detector or an ultraviolet lamp with dye) is almost impossible.
- 🔍 Visual inspection: Carefully inspect all accessible copper tubes, especially in places of bends and connections, for greasy stains.
- 👂 Auditory test: With a strong leak, you can sometimes hear a characteristic hissing or whistling, especially if you listen in silence.
- ❄️ Analysis of the freezer: If a “snowdrift” appears in the freezer only on one side or corners, this may indicate where gas is leaving the system.
The process of restoring the tightness involves finding the fistula, sealing it, evacuating the system and filling with a new portion of freon. Refilling Without eliminating the cause of the leak, this is only a temporary measure that will not solve the problem radically. It is important to find and eliminate the source of gas loss, be it corrosion or mechanical damage.
⚠️ Attention: Freon is a chemical substance, working with which requires a license and special equipment. Self-refilling with cans from car dealerships often leads to damage to the compressor due to the presence of moisture and oil in low-quality gas.
Clogged capillary tube and filter drier
Another common reason why unit it hums, but does not cool, is clogging capillary tube. This element is a thin copper coil that serves as a throttle to sharply reduce the refrigerant pressure before entering the evaporator. The diameter of the tube is so small that even a microscopic particle of oxide or moisture that has turned into an ice plug can completely block the freon current.
Often, a blockage is accompanied by characteristic behavior: the refrigerator may begin to freeze after a long period of inactivity (for example, 8-10 hours turned off), when the ice plug has time to melt. But as soon as you turn it on again and the moisture freezes in a narrow place, the cold disappears. This phenomenon is called "water hammer" or "ice jam". The filter-drier standing in front of the capillary is designed to retain moisture, but over time its resource is exhausted, and it itself becomes the cause.
How do craftsmen eliminate capillary blockage?
To purify the capillary tube, craftsmen use a special press with nitrogen. The pressure can reach 20 atmospheres. A method of freezing the suspected blockage with liquid nitrogen or chilled refrigerant is also used to expand the plug and push it through. At home, these methods are unavailable and dangerous.
You can diagnose a blockage by the temperature of the filter-drier (copper barrel near the compressor). Normally it should be warm, approximately the same as body temperature. If it is cold or covered with frost, there are signs of a blockage in the system. Also, when there is a blockage, you can often hear gurgling or periodic changes in the sound of the motor.
Removing the blockage requires professional purging of the system with nitrogen under high pressure and mandatory replacement of the filter-drier. Simply “blowing through” with your mouth or a tire compressor will not work here - you need to create a pressure that exceeds the working pressure in order to break through the obstruction. After the procedure, the system is evacuated again and refilled.
Malfunctions of the compressor and start relay
It also happens that it only seems to us that the compressor is working normally. In fact, it may hum, but not develop the necessary pressure to circulate freon. This is called "loss of productivity". The piston group could wear out, the valves could burn out, or the valve plate could break. In this case, the motor creates vibration and noise, but is not able to “pump” gas.
Often the culprit of the problems is starting relay. This is a device that supplies an impulse to start the motor windings. If the relay is faulty, the compressor may try to start, hum for a few seconds, then click and shut off. Or it will start, but will work only on one winding, which sharply reduces its efficiency and leads to overheating.
Checking the relay is quite simple: you need to remove it and shake it. If a ringing sound is heard inside (as if from broken ceramics), then the device definitely needs to be replaced. However, even a visually intact relay may not work correctly. It is also worth checking the contacts on the compressor itself - they could have oxidized or burned, creating a high contact resistance.
☑️ Primary diagnostics of the motor
If the diagnostics showed that it is compressor faulty (for example, a breakdown to the housing or an interturn short circuit), then replacing it is the only way out. This is a complex process requiring re-soldering of tubes, evacuation and refilling. It is not recommended to change the motor yourself without the skills of soldering copper and working with a vacuum pump.
Problems of the defrosting system in No Frost
In refrigerator systems No Frost lack of cold when the compressor is running is often associated with a malfunction of the system defrost. If the heating element (heating element) burns out, or the defrost sensor is stuck, or the timer/control module stops initiating defrosting, the evaporator becomes covered with ice. This ice blocks the air channel, and cold air simply cannot enter the main chamber.
Visually this manifests itself as follows: it may be cold in the freezer (since the evaporator is there), but it is warm in the refrigerator compartment. Or you hear that the fan (if there is one) is humming, but no air is blowing. After a while, when there is too much ice, it can also block the fan, and then the hum will be replaced by silence, although the compressor will continue to work.
For diagnostics, you need to defrost the refrigerator manually during the day (completely, not just turn it off at night). If, after complete defrosting, the unit began to freeze like new, but after 1-2 weeks the problem returned, look for a malfunction in the defrost circuit: heating element, defrost sensor or thermal relay.
| Symptom | Probable cause | Characteristic symptom |
|---|---|---|
| Frost only at the entrance of the pipes to the freezer | Freon leakage | The condenser at the back is cold |
| The compressor is hot, but does not freeze | Clogging capillary | The filter drier is covered with frost |
| There is cold, but weak | The door does not close tightly | Increasing "fur coat" at the junction of the doors |
| Motor turns on and turns off immediately | The starting relay is faulty | A loud click is heard |
When you need to call a technician
There are a number of situations when self-repair is not only useless, but also dangerous. If you have checked the thermostat, made sure that the seals are intact and there are no ice plugs, but the refrigerator still does not freeze, most likely the problem is within the sealed circuit. Opening sealed tubes without skills will only lead to moisture getting into the system, which will require even more complex repairs.
It is also worth contacting professionals if you need to replace the compressor. This process requires not only physical strength, but also the presence of a pressure gauge station, a vacuum pump, scales for accurate refilling of freon and a torch for soldering copper pipes. Errors at the vacuum stage (incompletely removed moisture) will lead to rapid re-breakage.
Do not ignore warranty obligations. If your refrigerator is less than 3-5 years old (depending on the brand), any DIY repair will void the warranty. In such cases, the only right decision would be to contact an authorized service center, even if the breakdown seems minor.
⚠️ Attention: The information in the article is for informational purposes only. The design of refrigerators from different brands (Indesit, Bosch, LG, Samsung) may differ significantly. Always check the technical documentation of your model before starting work.
Frequently asked questions (FAQ)
Why a refrigerator hums, but does not freeze after defrosting?
If after complete defrosting (more than 24 hours) the refrigerator turned on, worked for a couple of hours and stopped freezing, while the motor continues to hum, this almost certainly indicates freon leak or clogging of the capillary tube. Short-term operation is explained by residual pressure in the system or temporary melting of the ice plug.
Is it possible to operate a refrigerator if it does not freeze, but works?
Strongly not recommended. Operating without a heat sink (if it doesn’t freeze, it means heat isn’t being removed) leads to overheating of the compressor. This can cause insulation melting, motor jamming and a fire hazard. In addition, the food in the chamber will quickly deteriorate.
How much does repair cost if the compressor burns out?
The cost consists of the price of a new motor, the cost of replacing it, refilling with freon and consumables. Usually this is 50-70% of the cost of a new refrigerator. In older models, it is often more economically feasible to buy new equipment than to change the compressor.
How to understand that it is the thermostat that is faulty and not something else?
The main sign of a malfunction thermostat is that the refrigerator either does not turn on at all (the light is on, the motor is silent), or it works non-stop, severely overcooling the food. If the motor is running, but there is no cold, the problem is most often in the freon circulation system.
What to do if after a power surge the refrigerator stops freezing?
Most likely, the control module has failed or the compressor winding has burned out. First of all, check if the engine starts. If you hear a hum but do not start, the problem is in the start relay or motor. If there is silence, the module or thermostat has burned out. Diagnostics with a multimeter is required.