The situation when the refrigerator is working, that is, the light is on, the engine is humming, but the inside is not cooling, is one of the most common and alarming for the owner. You open the door, and everything is warm, the food begins to spoil, and panic arises. This is a classic symptom of a violation of the cooling cycle, which can be caused by many factors: from banal defrosting to serious mechanical failure.
It is important to understand that if the compressor is humming, this does not mean that it is pumping refrigerant. Often the engine idles due to a gas leak or a blockage in the system. In other cases, the problem lies in the electrics, when the start relay cannot start the compressor at full power, and it only hums and heats up. Primary diagnostics will help you understand whether you can solve the problem yourself or whether you need to call a technician.
Before disassembling the unit, it is worth eliminating external factors. Check that the sealing rubber is tight, that the ventilation holes are not blocked by food, and that the temperature in the menu is set correctly. Sometimes the reason is simple: you accidentally turned on the fast freezing or defrosting mode, and the automation temporarily turned off the cooling of the main chamber.
⚠️ Attention: If you smell a strong plastic smell or see sparking in the compressor area, immediately unplug the device. Further operation may lead to a fire or failure of the wiring in the apartment.
The main reasons for the lack of cold in a properly working refrigerator
The most common reason why The refrigerator does not freezebut it works is a refrigerant leak. Freon circulates through a system of tubes, picking up heat. If a microcrack appears in the circuit, the gas evaporates and cooling stops. At the same time, the compressor continues to hum, trying to pump what is no longer in the system. It is difficult to determine a leak visually; special equipment is often required.
The second common option is clogged capillary tube. Oil circulates in the system along with freon. Over time, the oil may thicken or ice may form in the tube due to moisture. This blocks the flow of refrigerant. The compressor is overloaded, trying to push gas, but there is no circulation. In such cases, the bottom of the refrigerator may be hot, but the evaporator is only partially cold.
The third important element is the thermostat or electronic control module. If temperature sensor fails, it may send the wrong signal that the chamber is already cold enough. As a result, the compressor either does not turn on at all, or operates in very short cycles, not having time to cool the chamber volume. In modern models with the system No Frost sophisticated electronics are responsible for this.
⚠️ Attention: Do not try to solder the tubes yourself or add freon without vacuuming the system. The residual moisture inside will turn into acid and destroy the compressor in a few months.
The hidden danger of freon leakage
Freon itself is not toxic in small quantities, but it displaces oxygen. In a small kitchen area, a large leak can cause concentrations that can cause suffocation. In addition, contact of freon with an open flame (gas stove) leads to the formation of phosgene, a poisonous gas.
Diagnostics of problems with the compressor and start relay
When you hear that the compressor is hummingbut the start does not occur (a click is heard and the buzzing subsides), the problem most often lies in the start-protection relay. This is a small device that gives a starting impulse to the motor. If it burns out, the motor cannot go from rest mode to operating mode. Replacing the relay is one of the simplest and cheapest repair procedures.
However, if the relay is working properly and the compressor still does not start or works but does not create pressure, an interturn short circuit of the windings is possible. In this case, the motor may become very hot, and the current consumption will be higher than normal. You can check the integrity of the windings with a multi-MRT by measuring the resistance between the contacts. Normal values usually range from 10 to 30 ohms, depending on the model.
In modern inverter models, the situation is more complicated. There is no classic starting relay, but the inverter moduleis responsible for starting. If it fails, the compressor may not receive the required speed to rotate. Diagnostics of such systems requires connection to the service port and the presence of special software, so there is little you can do here with your own hands.
☑️ Compressor diagnostics
System problems defrosting in No Frost refrigerators
In units with a system No Frost the lack of cold is often associated with a malfunction of the evaporator defrost system. Ice builds up on the evaporator, which is hidden behind a plastic panel in the freezer. If the defrost heating element, timer or defrost sensor breaks, the ice will not melt. After a while, the ice coat becomes so thick that it blocks the channels for blowing cold air.
As a result, the fan hums, the compressor works, but cold air simply does not enter the refrigerator compartment. The food in the freezer may still be retained due to residual cold, but the main compartment will be warm. A characteristic sign is the whistling or noise of a fan trying to blow air through the ice plug.
To check, you need to defrost the refrigerator for 24 hours (at least 10-12 hours). If, after complete defrosting, it began to freeze normally, but after 1-2 weeks the problem recurred, it means that the defrosting system is not working. It is necessary to change the heating element, defrost sensor or check the control circuit.
| Symptom | Probable cause | Check method |
|---|---|---|
| Evaporator covered with ice | Faulty heating element defrost | Ring the heating element with a multimeter |
| The fan is noisy | Ice interferes with the blades | Visual inspection after removing the panel |
| It’s cold only at the back walls | Air ducts are clogged | Checking the air flow by hand |
| Continuous operation of the compressor | Faulty defrost sensor | Measurement of sensor resistance |
Malfunctions of the thermostat and electronic control
In older models of refrigerators, the mechanical one is responsible for turning the compressor on and off thermostat. This is a device with a capillary tube that senses temperature. If the thermostat is stuck in the off position, the compressor will not receive a command to start. If it is faulty and does not open the circuit, the refrigerator will freeze until a fur coat forms.
In electronically controlled models (Full No Frost, Smart refrigerators), the role of a thermostat is performed by sensors (thermistors). They change their resistance depending on the temperature. If the sensor is lying, the control module receives false data. For example, the sensor shows +5°C, although the chamber is +15°C, and the compressor does not turn on.
Often the problem lies not in the sensor itself, but in oxidation of the contacts or a break in the wiring going to it. Vibration during compressor operation breaks down connections over time. It is also worth checking the control board: swollen capacitors or burnt tracks may block the signal from the actuators.
⚠️ Attention: When replacing the thermostat, it is important to correctly install and secure the capillary tube. If it does not fit tightly to the evaporator or is damaged, the new thermostat will also not work correctly.
Refrigerant leak: how to detect and what to do
Freon leak is the “silent killer” of the refrigerator. Gas can escape through microcracks in the foamed part of the housing or in places where the condenser tubes are soldered. Since freon is colorless and odorless, it is almost impossible to detect it visually. The main sign is that the refrigerator runs constantly, but does not freeze, and the condenser (grid at the back) remains only partially cold or warm.
Sometimes the location of the leak can be found by oily stains. Freon circulates in the system along with oil, and where the gas escapes, a trace of oil often remains. Inspect all accessible tubing, especially connections and elbows. If you find such a stain, the likelihood of a leak is high.
It is impossible to refill the refrigerator yourself. Required:
- Find the location of the leak (often using nitrogen pressure testing).
- Eliminate the defect (soldering or replacing the unit).
- Vacuum the system to remove moisture and air.
- Fill the exact amount of refrigerant according scales.
Mechanical damage and blockages of the system
Clogging of the capillary tube is the second most common cause after leaks. In a narrow channel with a diameter of less than a millimeter, a piece of solder left over from factory assembly or a clot of thickened oil can get stuck. This creates a traffic jam. The compressor tries to push freon, it hums, but there is no circulation. A characteristic sign is a hot compressor and only the first part of the evaporator is cold.
Mechanical damage often occurs due to inaccurate defrosting. If you chop the ice with a knife or pick at the evaporator, you could puncture the thin-walled tube. In this case, freon comes out quickly, sometimes with a hiss. You cannot operate such a refrigerator: moisture and air will get inside the system, which will lead to corrosion from the inside.
It is also worth mentioning the damage to the door seal. If the elastic is torn or does not fit, warm, moist air constantly enters the chamber. The compressor runs non-stop, trying to compensate for the heat, but cannot cope. A thick layer of ice forms on the walls, which further worsens heat transfer.
Why can’t you break through the ice with a knife?
Aluminum evaporator tubes are very thin. A slight movement with a sharp object leads to a through hole. Repairing such damage is difficult and expensive; sometimes it’s easier to buy a new refrigerator than to change the evaporator and refill the system.
Frequently asked questions (FAQ)
Why does the refrigerator hum, but does not freeze after defrosting?
If you defrosted the refrigerator for less than 8-10 hours, there could be moisture remains. When turned on, it froze in the capillary tube, creating an ice plug. The thermostat or starting relay could also fail due to a power surge when turned on.
How long should a new refrigerator cool down before turning on?
If the refrigerator was transported lying down, it needs to stand upright for at least 4-6 hours (in winter up to 12 hours) so that the oil flows into the compressor. If standing, 2-3 hours are enough for acclimatization.
Is it possible to use a refrigerator if it does not freeze, but the light is on?
It is highly not recommended. The compressor will run idle, overheat and may burn out. In addition, the food will spoil. It is better to turn off the device and carry out diagnostics.
What to do if it is warm in the refrigerator and cold in the freezer?
This is a sign of a malfunction of the defrost system (in No Frost) or a freon leak/clog (in drip systems). The freezer stays cold longer. A specialist's diagnosis is required.