Correct functioning of the cooling system in household refrigerator Indesit directly depends on the correct operation of the thermostat. This small but critical element acts as the “brains” for the compressor, determining when to start the refrigeration cycle and when to stop the unit to maintain the desired temperature. If you notice that the food in the chamber has begun to deteriorate faster than usual or, conversely, to freeze, the first thing you should pay attention to is the temperature sensor.
In this article we will analyze in detail the internal structure of the thermostat, the principles of its interaction with the rest of the refrigeration unit and typical scenarios for its failure. Understanding how exactly thermostat reacts to changes in heat will allow you to independently diagnose the malfunction without calling a technician. This knowledge will save time and help avoid wasting money on repairs.
Main purpose and principle of operation of the device
Thermostat, often called a thermostat, is an electromechanical or electronic relay that closes and opens an electrical circuit depending on the temperature of the sensitive element. Classic refrigerator models Indesit most often use mechanical devices that operate on the basis of expansion and compression of gas or liquid inside a capillary tube. When the temperature in the chamber rises above the set threshold, the working fluid expands, creating pressure that closes the contacts and starts the compressor.
The reverse process occurs when the air inside the refrigerator is cooled to the desired value. The pressure in the capillary system drops, the spring opens the contacts, and power to the engine stops. The key element here is the capillary tube, which must be tightly fixed to the evaporator for accurate reading data. Any displacement of this tube or violation of its tightness leads to incorrect readings and malfunctions of the entire unit.
Modern models can be equipped with electronic analogues, where the role of a sensitive element is played by a thermistor - a resistor that changes its resistance when the temperature changes. Such systems are more accurate, but more difficult to diagnose without special equipment. Mechanical regulators are reliable and repairable, which makes them popular in budget and mid-range equipment lines Indesit.
⚠️ Attention: When diagnosing a mechanical thermostat, do not try to forcefully bend the capillary tube or expose it to extreme heat, as this can lead to depressurization of the system and leakage of freon.
The internal structure of a mechanical thermostat
The design of a standard mechanical temperature controller is quite simple, but requires precise adjustment. The main components are a bellows chamber filled with refrigerant and a contact system controlled by a lever mechanism. The bellows reacts to changes in gas pressure in the capillary tube, transmitting force to the moving contact. When the pressure reaches a critical point, a click occurs and the circuit is closed.
The most important part of the design is the adjusting screw, accessible from the outside through the control knob. By rotating this knob, the user changes the tension of the spring, which affects the amount of pressure required to close the contacts. Thus, you set the temperature at which the compressor should turn on. The internal circuit also includes a bimetallic plate, which is responsible for opening the circuit when the lower temperature limit is reached.
The tightness of the bellows and capillary tube is absolute condition the operability of the device. If a microcrack forms in the system, gas will escape and the thermostat will stop responding to the heat in the chamber. In this case, the contacts will either remain constantly open (the refrigerator will not turn on) or closed (the unit will work without stopping).
The secret of calibration
Indesit thermostats are factory calibrated for a specific type of refrigerant. Replacing freon without reconfiguring or replacing the thermostat can lead to incorrect operation of the compressor.
Types of thermostats used in Indesit
In refrigerators of the brand Indesit you can find several modifications of thermostats, which differ in the method of fastening, the length of the capillary tube and the temperature response range. Understanding the differences between them is necessary when selecting a replacement part. Most often, single-chamber and two-chamber models are used, where control can be concentrated in one block or divided.
The table below shows the main differences between the types of thermostats:
| Device type | Principle of operation | Where installed | Features |
|---|---|---|---|
| Mechanical TAM | Gas-filled bellows | Inside the chamber or outside | Noisy click, high reliability |
| Electronic (thermistor) | Change of resistance | On the back wall of the camera | Quiet operation, high accuracy |
| Dual-circuit | Control of two zones | Upper part of the case | Regulates the refrigerator and freezer compartments |
Mechanical models of the series TAM or K are the most common in old and medium-sized models. They have a characteristic adjustment knob inside the refrigerator compartment. Electronic sensors are more often found in models with a system No Frost and a display on the front panel. Replacing one type with another is impossible without serious alteration of the electrical circuit and design changes.
Symptoms of a thermostat malfunction
Diagnostics of a thermostat breakdown often does not require disassembling the unit, since the symptoms appear in the compressor operating mode. The first alarm bell is a change in the cyclicity of engine operation. If the refrigerator turns on too rarely or, on the contrary, hums almost without interruption, the problem may lie precisely in the temperature sensor.
Let's consider the main signs indicating the need to check or replace the element:
- ❄️ The compressor does not turn on at all, although the light is on and the network hum is heard - this indicates that the thermostat contacts are constantly are open.
- 🌡️ The unit works without stopping, forming a “fur coat” on the back wall - the thermostat does not open the circuit, “not feeling” the achieved cold.
- 💧 The appearance of puddles under the refrigerator or severe freezing of ice in the chamber is a consequence of a violation of the temperature regime due to a failure sensor.
- 🔌 Spontaneous switching on and off at short intervals is a sign of “sticking” contacts or loss of bellows tightness.
It is important to distinguish a breakdown of the thermostat from a malfunction of the compressor itself or the starting relay. To do this, you can carry out a simple test: if when you close the thermostat wires directly (bypassing the sensor), the compressor starts and cools normally, then the problem is definitely in the regulator. However, this method requires compliance with safety precautions.
⚠️ Attention: Direct short-circuiting of the thermostat wires to test the compressor should only be done briefly. Prolonged operation without temperature control will lead to defrosting of food or freezing of the evaporator.
Instructions for checking and replacing the thermostat
If symptoms indicate a malfunction of the thermostat, it is necessary to conduct a visual inspection and check the electrical circuit. Before starting any work, the refrigerator must be disconnected from the power supply. Access to the thermostat is usually located inside the refrigerator compartment under a plastic cover or outside, on the back wall of the case, depending on the model. Indesit.
The diagnostic and replacement process includes the following steps:
- 🔧 Remove the regulator knob and protective cover to gain access to the device case.
- 🔌 Carefully disconnect the wires, first remembering or photographing their connection diagram.
- 📏 Check the integrity of the capillary tube: there should be no dents, traces of corrosion or oil.
- ⚡ Test the contacts: at room temperature they should be closed (for most models).
When installing a new element, it is important to correctly position the capillary tube. It should fit snugly on the evaporator in the same place where the original part was attached. Often special clamps or clips are used for fixation. If the tube dangles in the air, the temperature readings will be incorrect and the refrigerator will not work efficiently.
☑️ Check before assembly
After replacing and assembling all the components, you need to let the refrigerator run idle for several hours to make sure that the on and off cycles are correct. If the compressor starts and turns off in normal mode, and the temperature in the chamber stabilizes, the repair can be considered successful.
Setting and calibrating the temperature mode
After replacing the thermostat or during routine maintenance, it may be necessary to adjust the temperature mode. In mechanical models Indesit this is done by rotating the knob from minimum to maximum. However, it is worth remembering that the numbers on the handle are not degrees, but conditional ranges of cooling power.
For precise adjustments, it is recommended to use an external thermometer placed in a glass of water on the middle shelf of the refrigerator. After setting the knob to the middle position, wait 6-8 hours and check the readings. If the temperature differs from the desired one (usually +3...+5°C), you can ( — adjust) the position of the regulator. Electronic models are calibrated through the control menu, but often require service access.
Optimal setting extends the life of the compressor and ensures the safety of products. Too low a temperature causes the engine to work harder, and too high creates a risk of bacterial growth. Regularly checking the settings, especially in the summer or when the chamber is fully loaded, helps maintain balance.
Why the Indesit refrigerator does not turn off after replacement thermostat?
If after replacement the device continues to operate without stopping, you may have installed a thermostat with an inappropriate temperature response range. The cause may also be incorrect installation of the capillary tube - it does not fit tightly to the evaporator and does not feel real cold. In rare cases, the problem lies in a freon leak, and replacing the sensor will not help.
Is it possible to repair an old thermostat or just replace it?
Repairing mechanical thermostats at home is practically impossible and impractical. A bellows leak or a change in spring characteristics requires factory-installed recovery equipment. The cost of a new sensor is low, so replacing it with a new original or a high-quality analogue is the only correct solution.
How to understand that it is the thermostat that is broken and not the defrost sensor?
The defrost sensor is responsible for defrosting the evaporator in No Frost systems and is usually located on the evaporator itself. If it is faulty, the refrigerator may not go into defrost mode, which will lead to ice accumulation and stopping air circulation, but the compressor may continue to hum. The thermostat controls the start of the compressor itself. If the compressor is completely silent, we look at the thermostat; if it works but does not cool (due to ice), we look at the defrost system.