Many users habitually call the “twist” the same lever or wheel inside the refrigerator compartment that allows you to adjust the degree of cooling of products. However, few people realize that behind this simple appearance lies a complex mechanical or electronic mechanism, the serviceability of which determines the safety of your supplies. In everyday life, this unit is most often called a thermostat or thermostat, and it is this unit that acts as the main control element of the entire refrigeration system.
The operating principle of this device is based on constant monitoring of temperature indicators inside the chamber. When you turn the knob, you are actually setting a threshold value at which the compressor should stop or, conversely, start. Understanding how the spinner works in the refrigeratorwill help you avoid common mistakes during operation and independently diagnose some malfunctions without calling a technician.
It is important to note that modern models may differ significantly from old Soviet units in the type of sensors used. While the classic versions used a bellows tube containing gas, newer systems are increasingly using electronic sensors, although mechanical regulators are still popular due to their reliability. Let's look at the design details and operating principles of this important component.
The principle of operation of a mechanical thermostat
The basis of a classic mechanical regulator is a sealed system filled with a temperature-sensitive gas or liquid. This system, often called a bellows, is connected to a long capillary tube, the end of which is fixed on or in close proximity to the evaporator. It is this element that responds to changes in thermal conditions, transmitting a signal to the control mechanism.
When the temperature inside the chamber rises, the gas in the tube expands, creating pressure on the walls of the bellows. This pressure is transmitted to a system of levers, which closes the electrical contacts, starting refrigerator compressor. Conversely, when a predetermined low temperature threshold is reached, the gas is compressed, the pressure drops, and the contacts open, stopping the motor.
⚠️ Attention: The capillary tube of the thermostat is extremely sensitive to mechanical damage. Do not try to straighten it by force or bend it at an acute angle during installation, as a violation of the tightness will lead to complete inoperability of the unit.
By turning the adjustment knob, the user changes the tension of the spring inside the mechanism. This tension determines exactly how much gas pressure is required to open the contacts. Thus, the “twist” does not create cold, but only controls the duration of operation of the compressor, setting the range of temperature fluctuations.
Electronic temperature control systems
In more modern models of refrigerators, such as Liebherr or Bosch, mechanics give way to electronics. Here, instead of a gas-filled tube and bellows, thermistors are used - sensors that change their electrical resistance depending on the ambient temperature. This allows you to achieve much higher control accuracy.
The signal from the thermistor is sent to the main control module (board), which analyzes the data and makes a decision to start or stop the compressor. In such systems, the “twist” on the control panel is often just a touch switch that does not have a direct mechanical connection with the actuators. This makes it possible to implement additional functions, such as the “Vacation” mode or quick freezing.
The advantage of electronic systems is the ability to display the exact temperature in degrees, rather than conventional units from 1 to 7. However, the repair of such components requires specialized equipment for diagnosing the control board, while the mechanics can often be checked with a multimeter.
- 🔹 High accuracy of maintaining the specified parameters without significant fluctuations.
- 🔹 Possibility of integration with Smart Home systems and remote monitoring.
- 🔹 Reduced noise level during operation thanks to optimized startup algorithms.
- 🔹 Higher cost of spare parts and complexity of diagnostics at home.
Design and main components of the device
When considering the design of a mechanical thermostat, we can identify several key components, each of which performs its own function. The central element is the housing, inside which the contact group and the drive mechanism are located. It is here that the electrical power circuit of the compressor is switched.
The most important part is bellows chamber, which is deformed under the influence of refrigerant pressure in the capillary tube. This deformation is transferred to the moving contact. A spring, the tension of which is adjusted by the handle shaft, creates a counteraction, determining the switching point.
| Component | Function | Material |
|---|---|---|
| Capillary tube | Temperature signal transmission | Copper or brass |
| Bellows | Converting pressure into movement | Corrugated steel |
| Contact group | Electrical circuit switching | Silver, copper alloys |
| Adjusting screw | Changing spring tension | Coated steel |
It is also worth mentioning the differential - a parameter that determines the temperature difference between turning on and off. In some models, this parameter is fixed, in others it can be adjusted with an additional screw, access to which is often closed with a seal.
Diagnostics of thermostat malfunctions
You can determine that the “twist” has failed by a number of characteristic signs. The most obvious symptom is the absence of cold when the compressor is running or, conversely, the continuous operation of the motor without turning off. In the first case, the contacts may simply not close; in the second, the springs may have stuck or lost their elasticity.
For an initial check, you can try knocking on the thermostat body with the handle of a screwdriver. If the compressor starts after the impact, it means the problem is in the contact group or the mechanism is stuck. This is a temporary solution that allows you to wait until you buy a new part, but does not eliminate the root of the problem.
⚠️ Attention: Before any manipulations with the electrical components of the refrigerator, be sure to disconnect the device from the network. Working with 220V voltage requires compliance with safety regulations.
More accurate diagnostics can be carried out using a multimeter in dial mode. To do this, you need to remove the thermostat, disconnect the wires and check for contact between the terminals at different positions of the handle and at different temperatures of the sensing element. If the contacts do not “ring” even in the cold (or do not open when heated), the part requires replacement.
Why does the thermostat click?
The characteristic click when the refrigerator is operating is the sound of the contacts opening or closing inside the thermostat. If the clicks become too frequent or, on the contrary, disappear completely, this is a reason to listen more carefully to the operation of the unit.
Instructions for replacing the temperature controller
Replacing the thermostat is a procedure that can be done with your own hands if you have basic tools and care. The first step should always be to completely defrost the refrigerator and unplug it. This will allow you to safely access the internal components and avoid a short circuit.
Next you need to dismantle the old device. It is important to remember or photograph the wiring diagram, since mixing up the contacts can lead to failure of the compressor or control board. The capillary tube of the new thermostat must be installed in exactly the same place where the old one was located, using standard fasteners.
☑️ Algorithm for replacing the thermostat
After installing the new part and assembling the case, you can turn on the refrigerator. It is recommended to set the temperature for the first time with a reserve, gradually reducing the value to prevent food from freezing. A full cycle of operation and reaching the mode may take several hours.
Rules for setup and operation
Many users mistakenly believe that the maximum value on the “twist” provides better cooling. In fact, setting the regulator to its extreme position causes the compressor to work almost non-stop, which leads to increased wear and the formation of an ice coat. The optimal position is considered to be the middle position, corresponding to a temperature of +4...+5°C.
Seasonality also plays a role. In the summer, when the ambient temperature is high, the refrigerator needs to work harder, so a slight shift of the regulator towards stronger cooling is allowed. In winter, on the contrary, in unheated rooms, mechanical thermostats may not turn on the compressor at all, since the room is colder than required inside the chamber.
For models with two chambers and one compressor, there is a cold redistribution system, where the “twist” controls the damper. In such cases, the setting affects the temperature balance between the freezer and refrigerator compartment, and you need to change it very carefully, in small steps.
Frequently asked questions (FAQ)
Why does the refrigerator not turn off after replacing the thermostat?
Perhaps the capillary tube is installed incorrectly and is not in contact with the surface of the evaporator, or it is selected thermostat with inappropriate temperature range. It is also worth checking whether the wires are mixed up when connecting.
What do the numbers from 1 to 7 on the regulator mean?
The numbers indicate the degree of cooling, not the temperature in degrees. Typically "1" is the minimum cooling (warmer) and "7" is the maximum cooling (cooler). The exact values depend on the refrigerator model.
Is it possible to repair an old thermostat?
At home, repairs are almost impossible due to the need to maintain the tightness of the gas system and accurately calibrate the springs. It is easier and more reliable to replace the unit with a new analogue.
How often should you change the thermostat?
The service life of a mechanical thermostat is on average 5-7 years of intensive use. However, with careful treatment and stable voltage in the network, it can last 10 years.