The situation when it is warm in the main chamber, but the freezer continues to operate as normal, causes confusion among most owners of household appliances. It would seem that if the motor is humming and the ice in the freezer is hard, then there should be cold in the upper compartment. However, the design of modern units, especially systems No Frost and dual-circuit models, involves separation of air or refrigerant flows, which leads to such asymmetrical breakdowns. Understanding the physics of the cooling process will help you quickly determine whether you can solve the problem yourself or whether it’s time to call a technician.
Most often, the reason lies not in a complete stop of the compressor, but in a violation of the refrigerant circulation or a failure in the damper control system. Unlike old Soviet models, where the cold simply rose, modern units require a precise temperature balance. If you notice that the food in the main chamber begins to deteriorate, and a “fur coat” is growing on the walls of the freezer, you cannot ignore this - the problem can progress and lead to the failure of an expensive compressor.
In this article we will analyze in detail the mechanical, electrical and systemic causes of the malfunction. We will look at how freon leakage affects the operation of different chambers, why the capillary tube becomes clogged, and how the electronic control module behaves in the event of sensor failures. You will also learn what initial diagnostic steps can be performed without disassembling the case.
Refrigerant leak: partial loss of efficiency
One of the most common reasons why a refrigerator stops cooling in the upper compartment is a freon leak. The refrigerant circulates in a closed circuit, and as its volume decreases, the pressure in the system drops. In dual-circuit systems or models with one compressor but separated evaporators, this occurs unevenly. First, cold ceases to be produced where the temperature requirements are less stringent, that is, in the positive chamber, while in the freezer there is still enough cold reserve to maintain minus values.
It is almost impossible to determine the leak visually, since freon is a colorless and odorless gas. However, there are indirect signs that will indicate a problem. If you notice that the motor is running almost non-stop, trying to get up to temperature, and the condenser (the grill at the back) is heating unevenly or remains cold, this is a sure sign of a lack of refrigerant. Also, an incomplete “snow” coating may form on the evaporator inside the freezer, covering only part of the tubes.
⚠️ Attention: Independently refueling the refrigerator without finding and eliminating the leak is a waste of money. The freon will simply leave through the same hole in a few days or weeks.
Accurate diagnosis requires the use of a leak detector or a nitrogen pressure test technique, which only a service engineer can do. If a leak is confirmed in the sealed circuit (inside the cabinet), repairs may not be economically feasible, as it will require replacing the evaporator or installing an external “crying” evaporator, which will ruin the aesthetics of the unit.
Clogged capillary tube or filter drier
There are narrow areas in the refrigerant circulation system that are sensitive to contamination. The capillary tube and filter drier are responsible for throttling and cleaning freon from moisture and debris. Over time, especially if there was once moisture in the system or poor repairs were made, ice plugs or oxide blockages may form in these components. This prevents the normal flow of gas, and it simply does not reach the evaporator of the main chamber in the required volume.
Symptoms of a blockage are very similar to a leak: the refrigerator is humming, the freezer is freezing (sometimes even excessively), and there is heat in the upper compartment. However, there is a nuance: with an “ice jam,” the operation may be cyclical not according to the thermostat, but according to the “freezing” principle. The unit may work, freeze, then start again. In this case, the filter drier is often covered with frost or, conversely, remains warm, which is not typical for proper operation.
Elimination of this malfunction requires professional intervention. The technician needs to:
- 🔧 Vacuum the system to remove moisture and freon residues.
- 🔧 Replace the filter drier with a new one, since the old one is already saturated with moisture.
- 🔧 Blow out the capillary tube with nitrogen under high pressure or replace it.
- 🔧 Fill the system with a new volume of refrigerant strictly by weight.
Attempts to “defrost” the refrigerator in the hope that the ice plug will melt give only a temporary effect. After a few hours or days, the cycle will repeat, since the source of moisture or pollution will not go away. Moreover, operating the compressor in overload mode with a clogged system can lead to its thermal breakdown or mechanical destruction of the valves.
Why can’t you just replace the filter yourself?
Replacing the filter-drier requires soldering copper tubes and evacuating the system. Without a vacuum sealer, air and moisture will remain in the tubes, which will instantly damage the new filter and cause a new blockage.
Malfunctions of the thermostat or temperature sensors
The electronics and mechanics of temperature control are the “brains” of your refrigerator. If it receives incorrect data, then the commands will be incorrect. In older models, a mechanical thermostat is responsible for this, in modern ones - electronic sensors (thermistors). If the main chamber sensor “lies” and shows that there is already -5°C, although in fact it is +10°C, the compressor simply will not turn on to cool the upper compartment (in dual-circuit systems) or will work too little.
In refrigerators with the system No Frost there is often a situation when the sensor “sees” cold only in the freezer area where it is located, and ignores the temperature in the positive compartment. This can happen due to sensor displacement, broken wiring, or failure of the element itself. In mechanical thermostats, the problem may lie in a loose bellows tube or a leak in the regulator capillary.
Diagnostics of the sensors is carried out using a multimeter by measuring the resistance at different temperatures. For mechanical thermostats, check the contacts for closure when the sensing tube cools. If you do not have the skills to work with electrical measuring instruments, it is better not to take risks, since an error in diagnostics will lead to the replacement of a serviceable but expensive spare part.
Problems with the Air Control damper in the No Frost system
In refrigerators with cold distribution No Frost or Total No Frost cold air is generated in the freezer, and then through special channels it is supplied to the main compartment. The flow is adjusted by a damper (damper), which opens and closes at the command of the electronics. If this damper gets stuck in the closed position or the drive motor fails, the cold simply will not get into the upper chamber, remaining “locked” in the freezer.
Signs of a malfunctioning damper are quite typical: the freezer operates in high mode (since the sensor there requires cold), and the refrigerator compartment is quiet and warm. Sometimes you can hear a crackling or humming noise in the area of the air duct between the chambers - this is the motor trying to move the jammed damper. The problem may also be in the electronics themselves, which do not send a signal to open.
To check, you need to gain access to the air duct, which is usually hidden behind a plastic panel on the back wall of the refrigerator compartment or at the top. A visual inspection will show whether the damper is open. If it is mechanically movable, but does not respond to commands, the drive will need to be replaced or the control circuit checked.
| Symptom | Possible cause | Check method |
|---|---|---|
| Warm at the top, cold at the bottom | The damper is closed | Visual inspection of the air duct |
| A cracking sound is heard behind the wall | Attempt to open the damper | Listening to the motor operation |
| Ice at the entrance air duct | Freezing of the damper | Defrost 24 hours |
| The damper is open, but there is no cold | The fan is faulty | Checking the rotation of the blades |
Evaporator fan malfunction
In forced air circulation systems, the fan is the “heart” of cold distribution. If it stops, cold air remains in the evaporator unit (usually the back wall of the freezer), and natural convection is not enough to cool the main chamber. The freezer can freeze, since the source of cold is located directly in it, but food in the depths of the chamber can also begin to deteriorate.
The reasons for the fan stopping are varied: freezing of the blades, failure of the bearings, breakage of the winding, or a problem with the voltage supply. Often the fan becomes blocked by ice if the evaporator defrost system is not working correctly. In this case, the blades simply cannot turn. You may hear extraneous noise, grinding or complete absence of sound from the fan when the door is open (in some models it turns off when opened, in others it continues to work).
Checking the fan requires disassembling the back panel of the freezer. You need to make sure that nothing is blocking the rotation and check for voltage at the terminals. If the motor hums but does not turn, the bearing may be stuck and the part needs to be replaced. Operating a refrigerator with a non-working fan will lead to overheating of the compressor and incorrect temperature conditions in all chambers.
☑️ Fan diagnostics
The influence of the defrost mode and heating element defrosting
It would seem, what does defrosting have to do with it if the refrigerator does not freeze? However, in systems No Frost the cooling cycle and the defrosting cycle are closely related. If the defrost heating element, timer or defrost sensor is faulty, the evaporator becomes covered with ice. This ice blocks not only the evaporator itself, but also the air supply channels. As a result, the fan (even if it is working) cannot drive air through the ice shell, and the cold does not enter the main chamber.
Often owners notice that after the refrigerator is completely defrosted within 24 hours, it begins to work normally, but after 3-5 days the situation repeats. This is a classic sign of a faulty defrost system. The ice builds up again and again blocks the air flow. The freezer can continue to freeze for some time due to residual cold or direct contact with the evaporator, but the operating efficiency drops catastrophically.
Faulty elements can be:
- ❄️ defrost heating element (burnt-out spiral).
- ❄️ Defrost sensor (does not “see” that the ice has melted, or does not give a command to turn on the heating element).
- ❄️ Thermal relay (protecting the heating element from overheating).
- ❄️ Control module (does not send signals).
⚠️ Attention: If you defrosted the refrigerator and it started working, but after a week it stopped cooling again in the upper compartment, do not delay the repair. Constant freezing leads to deformation of plastic parts and air duct channels.
Frequently asked questions and answers (FAQ)
Could the problem be in the sealing rubber band of the main chamber?
Yes, if the rubber band is worn out or the door is skewed, warm air constantly enters the chamber. The compressor may not be able to cope with the heat flow, creating the illusion of a breakdown, although in fact the seal is broken. Check whether the door fits tightly around the entire perimeter.
Why did the refrigerator work after defrosting, but not for long?
This indicates a cyclic problem, most likely associated with the defrost system (No Frost) or a freon leak. Defrosting temporarily removes the ice plug or allows the remaining freon to be distributed, but the root of the problem (faulty sensor, heating element or hole in the circuit) remains.
How long do you need to wait after turning on for cold to appear?
Usually it takes from 4 to 12 hours to stabilize the temperature, depending on the volume of the chamber and ambient temperature. If after 12 hours of compressor operation it is warm in the main chamber and cold in the freezer, there is a technical malfunction.
Is it dangerous to continue using such a refrigerator?
For a short time - yes, food can be transferred. But long-term operation is dangerous for the unit itself. The compressor, working non-stop or in abnormal mode, can burn out, which will lead to much more expensive repairs or the purchase of new equipment.
Is it possible to replace the thermostat yourself?
If you have a mechanical thermostat and have access to it, it is possible. However, in modern models with electronic control and hidden sensors, replacement requires disassembling the case and diagnostics, which is better to entrust to a specialist so as not to break the seal or damage fragile plastic elements.