Modern refrigeration units with an automatic defrosting No Frost are radically different from old models with a crying evaporator. This technology is based on forced air circulation, which is provided by a special fan. It is this unit that forces cold air to move through all chambers, creating a uniform temperature background and preventing the formation of an ice crust on food.
If you have ever listened to the operation of your refrigerator, you have probably noticed a characteristic hum that occurs periodically. This is the sound of the working evaporator fan (evaporator fan). Understanding exactly how this mechanism functions will help you quickly diagnose problems with cooling or increased noise, without calling a technician at the first suspicious sound.
Unlike natural convection, where cold air simply falls down, the system No Frost actively moves gas masses through the evaporator. The fan turns on synchronously with the compressor or by a signal from the defrost sensor, providing instant distribution of cold immediately after opening the door. Without this component, the refrigerator would turn into an ordinary cabinet with local cooling at the back wall.
Fan design and location
In most models of refrigerators, be it LG, Samsung or Bosch, the fan is a compact electric motor with an impeller. It is hidden from the user's eyes and is located behind the rear panel of the freezer. You can get to it only by removing the protective plastic, which requires caution so as not to damage the fragile latches.
Structurally, the unit consists of the motor itself, a plastic impeller and a volute body, which directs the air flow in the desired direction. Impeller often has a specific blade shape, designed to create a certain pressure and minimize aerodynamic noise. The mounting is usually made on rubber vibration dampers so that vibration is not transmitted to the refrigerator body.
It is important to note that in dual-circuit systems No Frost two separate fans can be used: one for the freezer compartment, the other for the refrigerator compartment. In simpler single-circuit models, one powerful fan drives air through a system of channels blocked by dampers. The location of the motor is always chosen so that it does not come into contact with water formed during defrosting, although in older models this rule was sometimes violated, leading to oxidation of the contacts.
⚠️ Attention: Before attempting to remove the back panel, be sure to disconnect the refrigerator from the power supply. The rotating impeller and electrical contacts pose a danger if handled carelessly.
The principle of air circulation in the No Frost system
The operation of the cooling system is based on a continuous cycle. When the thermostat or electronic module gives a command to cool, the compressor starts and simultaneously (or with a slight delay) turns on fan. Cold air is taken from the evaporator area, where it is cooled as much as possible, and supplied under pressure to the chambers.
Air flows move through special air ducts located in the walls or under the housing casing. In the refrigerator compartment, air exits through the top vents, falls down to cool the food, and then returns back to the evaporator through the bottom ducts. This process ensures uniform temperature on all shelves, which is impossible in static systems.
The fan plays a special role in the defrosting process. In some modern models with the function Smart Defrost the fan can operate in reverse mode or simply stop, allowing the heat from the heating element to quickly melt the ice on the evaporator. After completing the defrost cycle and drying the heating element, the fan starts again, starting active cooling.
Table: Comparison of types of fans in refrigerators
| Characteristics | Axial fans | Tangential (centrifugal) | Fans with an EC motor |
|---|---|---|---|
| Principle of operation | Move air along the axis of rotation | They take air in the center and exhaust it along the periphery | Electronically commutated, with smooth startup |
| Noise level | Average, whistling of the blades is possible | High pressure, but can make noise when clogged | Minimum, quiet operation |
| Energy efficiency | Standard | Depends on design | High, low energy consumption |
| Where used | Budget and mid-range models | Large Side-by-Side refrigerators | Premium models Liebherr, Bosch |
Typical faults and their symptoms
The most common problem faced by refrigerator owners No Frostis the appearance of extraneous noise. This may be a hum, crackling, whistling or knocking. Often the reason lies in the wear of the plain bearings of the fan motor itself. Over time, the lubricant in them dries out, and the shaft begins to rotate with difficulty, making unpleasant sounds.
Another common situation is fan freezing. If the defrost system does not work correctly (the heating element, defrost sensor or timer is faulty), ice builds up on the evaporator and reaches the blades. Impeller begins to touch the ice crust, producing a loud cracking noise, similar to the operation of an airplane propeller. In this case, the fan may even stop, blocked by ice.
Complete motor failure leads to the fact that the refrigerator stops freezing, although the compressor may work properly. Without forced circulation, the cold does not reach the temperature sensor, and the unit works non-stop, trying to cool the volume, but to no avail. The food in the refrigerator compartment becomes warmer, and defrosting begins in the freezer.
⚠️ Attention: If you hear the cracking of ice, do not try to forcefully spin the fan or pick at the ice with a knife. You can damage the blades or the evaporator, which will lead to a freon leak.
Why can a fan hum after defrosting?
Sometimes after manual defrosting, water flows into the motor bearings. When it freezes, it blocks the shaft. It is necessary to let the refrigerator stand turned off for 24 hours to completely dry the internal components.
Diagnostics and performance testing
To understand why the fan does not work or is noisy, it is necessary to conduct a visual and technical inspection. First, remove the back panel in the freezer. Pay attention to the amount of ice. If the evaporator is coated and the fan is clean, the problem is in the defrost system and not in the fan itself. If ice has bound the blades, this is a consequence of the same problem.
Checking the electrical part requires the use of a multimeter. It is necessary to ring the motor windings for breaks or short circuits. In good condition, the winding resistance should be within a certain range (usually several hundred ohms), but the exact values depend on the specific motor model. It is also worth checking the free movement of the impeller: it should rotate easily, without jamming.
In modern electronically controlled models, diagnostics are often simplified. A fan error can be displayed or coded by blinking indicators. For example, in refrigerators Indesit or Atlant a certain combination of flashing lights indicates problems with air circulation or the fan motor.
☑️ Diagnosis of fan noise
Replacement and maintenance of the unit
If the diagnostics showed that the fan motor is faulty (the winding is burned out or the shaft is jammed), it must be replaced. Repairing bearings in such compact engines is usually impractical and time consuming. The new element must fully correspond to the original in terms of fit dimensions, supply voltage and direction of rotation.
The replacement process is as follows: the wires are disconnected (take a photo of the connection diagram first!), the fastening screws of the fan housing are unscrewed, and the old assembly is removed. The new one is installed in the reverse order. Pay special attention to the tight fit of the fan housing to the air duct so that there is no loss of air pressure.
To prevent problems with icing, it is recommended to regularly check the condition of the drainage hole. If it is clogged with debris or ice, the water does not go into the tray, but freezes below, gradually rising to the level of the fan. Cleaning the drainage with a thin brush or warm water helps to avoid expensive repairs.
The influence of the fan on energy consumption
Although the fan consumes significantly less electricity than the compressor, its influence on the overall energy balance of the refrigerator is great. Efficient circulation allows the set temperatures to be reached faster, after which the compressor switches off. If the fan is weak or the ducts are clogged, the operating time of the compressor increases, which leads to an increase in electricity bills.
In models with inverter motors, the fan can also change the rotation speed. When the door is closed and the temperature is stable, it can go to minimum speed, reducing noise and energy consumption. When loading warm food, the speed automatically increases for faster cooling.
Understanding how the fan in your refrigerator No Frostgives you an operating advantage. You will be able to distinguish normal operating noise from a malfunction signal, notice an icing problem in time and avoid food spoilage. Regular maintenance of the ventilation system is the key to long service life of the entire unit.
Why does the fan sometimes turn on when the door is open?
Many modern models have a reed switch (door opening sensor). When the door is opened, the fan should stop so as not to blow cold into the room and not freeze the food with warm air. If it continues to work, the sensor itself may be faulty or its adjustment is impaired.
Is it possible to operate the refrigerator if the fan is noisy, but freezes?
For a short time, it is possible. However, persistent noise indicates bearing wear or blade friction. Over time, the motor may become completely jammed, causing the chamber to defrost. In addition, friction can cause overheating and melting of plastic parts.
How often do you need to clean the fan from dust?
In the No Frost system, air circulates inside a closed circuit, so little dust gets there during normal operation. Cleaning is only required during repairs or if foreign objects have entered the chamber (for example, labels that have been sucked into the air duct). There is no special cleaning schedule.