A modern refrigerator is a complex engineering system in which each element performs a strictly defined function to maintain a given temperature regime. Understanding exactly what parts make up the internal structure of the unit is necessary not only for professional craftsmen, but also for ordinary users who want to extend the life of their equipment. Knowledge of the device allows you to quickly diagnose the cause of a breakdown, distinguish a minor defect from a serious malfunction and correctly plan the budget for repairs or replacement of components.
The bulk of household refrigerators, regardless of the brand and year of manufacture, are based on the compression principle of operation, where the refrigerant circulates in a closed circuit, changing its state of aggregation. There are many components hidden inside the case, from a massive motor-compressor to tiny temperature sensors, and the failure of even one of them can lead to food spoilage. In this article, we will analyze in detail what the “stuffing” of your refrigerator consists of, how different systems interact with each other, and what components should be paid attention to first when the first signs of a malfunction appear.
The heart of the system: the compressor and the start-up relay
The main element that ensures the circulation of the refrigerant is compressor, which is often called a refrigerator motor. This is an electromechanical pump that compresses freon gas, increasing its pressure and temperature, and pushes it into the condenser. Modern models most often use piston or inverter compressors; the latter are characterized by a smooth change in shaft rotation speed, which reduces noise levels and energy consumption. It is on the serviceability of this unit that the ability of the entire system to generate cold depends.
To start the engine and protect it from overloads, it is used start-protective relay, which is mounted directly on the compressor housing. This small element supplies a starting impulse to the motor winding and also opens the circuit when the rated speed is reached. If the relay fails, the compressor either does not start at all, making only a quiet click, or it hums for a few seconds and turns off due to thermal protection. In some cases, a malfunction of the relay can lead to the combustion of the windings of the motor itself.
⚠️ Attention: When replacing a compressor or relay, it is strictly forbidden to open the system without special equipment for pumping out air and refilling freon. An attempt to simply replace a part without evacuation of the circuit will lead to instant failure of the new compressor.
It is important to note that compressors come in different types, and their replacement requires precise selection of an analogue in terms of power and type of refrigerant. Inverter models, for example, they are controlled by an electronic unit, and their diagnosis requires special tools, unlike classic ones linear motors. If you hear a loud knocking or metallic clanging sound from the back of the unit, this is a sure sign of mechanical destruction of the internal parts of the compressor.
Heat exchange and circulation: condenser, evaporator and capillary
In addition to the motor, heat exchangers play a critical role in the refrigeration cycle, which ensure the transition of the refrigerant from one state to another. The condenser is a lattice of tubes, usually located on the rear wall outside the housing (although it can also be built into the side walls). Here, the compressed hot gas releases heat to the environment and condenses into a liquid. Contamination of the condenser with dust and animal hair is one of the most common causes of compressor overheating and increased energy consumption.
Inside the refrigerator or freezer is located evaporatorwhere liquid freon boils at low pressure, actively absorbing heat from the internal space. In No Frost systems, the evaporator is hidden behind a plastic panel and is equipped with a fan for forced air circulation. If the evaporator is overgrown with a thick “coat” of ice, this indicates problems with the defrost system or a freon leak, which requires immediate intervention.
A thin copper tube, called capillaryconnects these two nodes. It works like a throttle, creating the necessary vacuum in front of the evaporator. The diameter and length of the capillary are strictly calculated by the manufacturer for a specific model. Clogging of the capillary with oil oxidation products or moisture (ice plug) leads to the fact that the refrigerator stops freezing, although the compressor continues to work without interruption.
Defrosting system in No Frost refrigerators
In units with a system No Frost or Full No Frost the process of ice formation on the evaporator is prevented or eliminated automatically using a special defrosting cycle. The key element here is Defrost heating element (tubular electric heater), which turns on on a timer and melts the ice frozen on the evaporator. The resulting water flows into a special pan located above the compressor, where it safely evaporates.
Controls this process defrost timer or, in more modern models, an electronic control module that monitors the operating time of the compressor or the number of door opening cycles. Once the accumulated time reaches the set value, the system enters defrost mode. If the timer “sticks” in the cooling mode, the evaporator becomes overgrown with ice, blocking the air circulation channels, and the chambers become warm, despite the running motor.
Another important sensor in this chain is defrost thermostat (or bimetallic plate). It breaks the power supply circuit of the heating element when the ice has completely melted and the temperature on the evaporator has risen to positive (usually about +10...+15°C). This prevents overheating of plastic parts and the heating element itself. Failure of the thermostat in the open state leads to the fact that the heating element never turns on, and the refrigerator turns into a “snowdrift”.
☑️ Checking the No Frost system
Temperature control: thermostats and sensors
Various types of thermostats are responsible for maintaining the set temperature in the chambers. In classic single-chamber refrigerators and older models, a mechanical one is used. This is a device with a bellows filled with a sensitive gas that expands or contracts with changes in temperature, opening or closing electrical contacts. The user adjusts the compression force of the bellows using the knob, setting the desired mode. thermostat. This is a device with a bellows filled with a sensitive gas that expands or contracts with changes in temperature, opening or closing electrical contacts. The user adjusts the compression force of the bellows using the knob, setting the desired mode.
Modern multi-chamber units are equipped with electronic temperature sensors (thermistors) that transmit data to the main control module. Such sensors are highly accurate and allow the implementation of complex operating algorithms, for example, super-freezing or intelligent cold distribution. If the electronic sensor “lies” or shows an open circuit, the refrigerator can work non-stop, freezing food, or, conversely, turn off and defrost the contents.
Deserves special attention defrost sensor, which we have already mentioned in the context of the No Frost system, but in some models there may be several of them to control different evaporator zones. Replacing these elements requires precise selection of resistance at a certain temperature, since there are practically no universal solutions here. An incorrectly selected sensor will lead to incorrect operation of the entire cycle.
| Type of sensor/thermostat | Principle of operation | Typical malfunction | Symptom of failure |
|---|---|---|---|
| Mechanical thermostat | Gas compression in the bellows | Loss of bellows tightness | The refrigerator does not turn on |
| Thermistor (electronic) | Change in resistance | Open circuit or change in value | Error on the display, mode failure |
| Defrost thermostat | Bimetallic plate | Oxidation of contacts | Ice build-up in the freezer |
| Air temperature sensor | Semiconductor element | Drift of readings | Freezing or defrosting |
Ventilation and tightness: fans and seals
In refrigerators with a cold distribution system (No Frost, Frost Free), it is impossible to imagine working without of the fan. It is installed in the freezer and drives cold air through the ducts into the refrigerator compartment. There can be one fan (common) or two (separate for each chamber). If the fan impeller is covered with ice or its motor fails, air circulation stops, which leads to local overheating in one part of the chamber and severe freezing in another.
An equally important element that keeps the cold inside is sealing rubber (cuff) on doors. This is not just a piece of rubber, but a complex profile design with a magnetic insert, ensuring a tight fit of the door to the body along the entire perimeter. Over time, rubber hardens, cracks or stretches, ceasing to perform its function. Warm, moist air enters through a loosely closed door, causing increased ice formation and increased load on the compressor.
Also involved in the ventilation system are dampers (dampers), which regulate the amount of cold air flowing from the freezer into the refrigerator compartment. The damper is controlled by a separate motor or thermal drive. If the damper is stuck in the closed position, there will be heat in the upper chamber, and if it is open, all the food in the refrigerator compartment may freeze.
How to check the tightness of the door?
Take a sheet of A4 paper, clamp it with the refrigerator door so that part of the sheet hangs out. Try to pull out the sheet. If it is easily removed without resistance, it means that the seal in this place does not fit and requires replacement or adjustment of the hinges.
Electrical circuit and additional elements
The electrical circuit of the refrigerator includes not only power elements, but also control and indication components. Surge filter protects the electronics from surges in the household network, although in budget models it is often represented by a minimalistic set of capacitors. Light lamp the chamber is usually powered through a limit switch (or reed switch in new models), which opens the circuit when the door is closed. A malfunction of the switch can lead to the fact that the light is on constantly, heating the camera, or does not light up at all.
In models with a display and complex operating logic there is control module (board). This is the “brain” of the device, which reads the readings of all sensors and controls the operating mechanisms: compressor, fans, heating elements and valves. Board failure is often caused by voltage surges or moisture (condensation) getting on the contacts. Diagnostics of the module requires deep knowledge in electronics and the presence of circuits.
It is worth mentioning separately Freon line as a design. This is a closed system of copper and aluminum tubes. Aluminum tubes, often used in modern evaporators (Lockal), are extremely sensitive to mechanical stress and corrosion, unlike the more durable copper used in Soviet technology. Any microcrack in the line leads to a refrigerant leak, which makes the refrigerator impossible to operate without professional soldering and refilling.
⚠️ Attention: Technical characteristics of refrigerators, types of refrigerants used (R600a, R134a) and control circuits may vary depending on the specific model and year of manufacture. Before ordering spare parts, always check the part numbers with the technical documentation of your device or the markings on the nameplate.
Frequently asked questions (FAQ)
Is it possible to replace the compressor yourself without special equipment?
No, replacing the compressor requires the mandatory use of a vacuum pump to remove moisture and air from the system, as well as scales and a pressure gauge station for accurate refilling of freon. Without this, the refrigerator will not work or will quickly fail.
Why does ice freeze in the No Frost refrigerator if the system should be without ice?
Ice in the chamber with the No Frost system indicates a malfunction of the defrost system. Most often, the heating element, defrost timer or defrost thermostat burns out. It is also possible that the drainage hole through which water should flow into the pan may become clogged.
How often do you need to change the sealing rubber on the door?
The service life of the seal is on average 5-7 years, but depends on operating conditions. It needs to be changed if it has lost its elasticity, cracked or stopped holding the magnet, which leads to the compressor constantly turning on.
What does the humming of the refrigerator mean after the compressor is turned off?
Short-term humming or gurgling after the motor stops is normal. The refrigerant continues to flow in the tubes under the influence of the pressure difference, leveling the state of the system before the next start.