Many owners of household appliances are faced with a situation where the food in the chamber stops freezing or, conversely, turns into an ice ball. Often the root of the problem lies in one small but critical element of the control system. Thermostat in the refrigerator is a device that automatically maintains a set temperature by opening and closing the electrical circuit of the compressor.
If you are wondering what exactly this component does and why it is so important, then The answer is simple: it is the “brain” responsible for the operating cycles of the motor. Without it, the unit would work continuously, consuming a huge amount of electricity, or would completely stop cooling the contents. Understanding the principle of its operation will help you quickly diagnose a malfunction.
In modern models, such as Indesit, Atlant or Beko, this element can be mechanical or electronic. Regardless of the design, its task remains the same - to control the climate inside the chambers. In this article we will analyze in detail the device, operating principle and methods for checking the serviceability of the sensor.
The principle of operation of the thermostat in the cooling system
The main function thermostat is to monitor the air temperature inside the refrigeration chamber. Inside the device there is a sensitive element - a bellows filled with gas or liquid, which reacts to thermal expansion. When the air in the chamber heats up above the set threshold, the pressure in the bellows increases, the pusher is activated and closes the contacts, starting the compressor.
As soon as the temperature drops to a predetermined minimum, the process proceeds in the reverse order. The pressure drops, the contacts open and the engine stops. This cycle is repeated constantly, ensuring stable storage conditions for products. In electronic models, the role of a bellows is played by thermistor, changing its resistance depending on the heating.
It is important to understand that the thermostat does not measure the temperature of the products directly, it reacts to the air temperature. That is why, after loading a large amount of warm food, the work cycle may become more frequent. The system will work more intensely until it stabilizes the climate throughout the entire volume of the chamber.
⚠️ Attention: In some models with the No Frost system, the thermostat can control the temperature of the evaporator, rather than the air in the chamber. Installing an unsuitable sensor will result in incorrect defrost operation.
The difference between mechanical and electronic models is significant. Mechanical devices, often found in old refrigerators Zil or Biryusa, have a rotary handle and operate due to the physical properties of gas. Electronic analogues, typical for Samsung i LG, transmit data to the board, which itself makes the decision to start the motor.
Why does the thermostat click?
The click that you hear when the refrigerator is operating is the sound of the contacts opening or closing inside the thermostat. In mechanical models it can be quite loud. If clicks begin to occur too often (every 2-3 minutes), this may indicate a loss of tightness of the bellows or a refrigerant leak, due to which the sensor does not “feel” the required pressure.
Main functions and tasks of the device
The main task of the component is to maintain balance. It doesn’t just turn the motor on and off, it protects the system from overloads and food from spoilage. Temperature adjustment occurs within a given range, which is usually from 0 to +8 degrees in the main chamber and from -18 to -24 in the freezer.
In addition, the device provides energy saving. If the compressor worked without interruption, the electricity bill would increase significantly, and the engine's life would be exhausted in a few months. The thermostat allows the unit to “rest” up to 70% of the cycle time, which is especially important at night or in winter.
- 🌡️ Control of the upper and lower threshold of temperature values for different storage zones.
- ⚡ Protection of the compressor from idling and excessive wear.
- 🧊 Preventing food from defrosting during power surges or heating.
- 🔔 Fault signaling (in electronic systems) through indication on the display.
Two-chamber models often use one thermostat, which is installed in the refrigerator compartment. The freezer compartment is cooled according to the residual principle. That is why, if you set the temperature in the refrigerator too low, it can drop to extreme values in the freezer.
Types of thermostats: mechanical and electronic
There are two main types of regulators on the household appliances market. Mechanical devices are reliable, inexpensive and easy to diagnose. They are a sealed system with a capillary tube that leads into the chamber. Inside the tube there is freon or another gas, which, when heated, expands and presses on the membrane.
Electronic thermostats, or thermistors, are semiconductor elements. They have no moving parts or tubes. Their resistance changes smoothly, and the board reads these changes with high accuracy. Such systems are typical for models with displays and the Smart function.
The table below will help you understand the differences and diagnostic features:
| Characteristics | Mechanical thermostat | Electronic sensor (Thermistor) |
|---|---|---|
| Principle of operation | Physical expansion of gas/liquid | Change in electrical resistance |
| Accuracy | Average (error 1-2 degrees) | High (error 0.1-0.5 degrees) |
| Location | Often inside the camera, the handle is visible | Hidden behind the walls, control on the panel |
| Repairability | Replacing the entire assembly | Replacing the sensor or flashing the board |
Mechanical models, such as Tam 112 or K59are often marked with colored dots on the handle. Electronic systems require a multimeter and knowledge of resistance ratings at different temperatures to test. An error in choosing the type of sensor when replacing will lead to incorrect operation of the entire unit.
Symptoms of a malfunctioning thermostat
You can understand that refrigerator thermostat it has failed by indirect signs. The most obvious symptom is that the unit stops turning off. The compressor hums continuously, trying to reach an unattainable temperature. This often happens when the contacts inside the sensor “stick” in a closed state.
The opposite situation - the refrigerator does not turn on at all. In this case, the circuit is open, and the signal to start the engine simply does not arrive. Sometimes the device works, but the cycles become too short or too long. Products in the chamber can either thaw or become covered with frost.
- ❄️ Formation of a “snow coat” or ice crust on the back wall.
- 🔊 The compressor works without stopping or does not start at all.
- 💧 Appearance puddles of water under the refrigerator due to frequent defrosting.
- 🌡️ The temperature in the chamber does not correspond to the position of the regulator.
⚠️ Attention: If the refrigerator does not turn on, do not rush to change the thermostat. First, check the integrity of the wiring and the presence of voltage in the outlet. Often the problem lies in the start relay or the compressor itself.
In electronic models, a sensor malfunction is often indicated by an error code on the display. For example, this may be a code indicating an error in the refrigerator or freezer compartment sensor. You should always look for decoding of the codes in the instructions for a specific model. Samsung this could be the code 21C or 23C, indicating an error in the refrigerator or freezer compartment sensor. The decoding of the codes should always be found in the instructions for the specific model.
How to check a thermostat with a multimeter
For accurate diagnostics, you will need a multimeter set to resistance measurement mode (Ohm). Before starting work, be sure to disconnect the refrigerator from the power supply! Remove the thermostat housing and locate the contacts going to the compressor. Usually there are two or three of them.
If the thermostat has a third contact, it is often responsible for the indicator light or engine starting. To check the main contacts (usually marked 3 and 4 or have the colors of the wires) connect them together. If after this the refrigerator starts working, the problem is almost certainly in the regulator.
Checking with a multimeter is carried out as follows:
- Remove the regulator and immerse its sensitive tube in a container with warm water (about +40°C).
- Touch the multimeter probes to contacts.
- If the device shows "0" or a value close to zero, the circuit is closed, the device is working.
- When the tube is cooled (place it in the cold), the resistance should increase to infinity (open circuit).
In electronic thermistors, the resistance is checked at room temperature. It must correspond to the rating specified in the technical documentation (for example, 5 kOhm or 10 kOhm). As your hands heat up, the resistance should change smoothly. There should be no jumps.
Replacing the thermostat with your own hands
If diagnostics have confirmed a malfunction, replacing the thermostat is a procedure available to a home handyman. The main thing is to choose an analogue with identical parameters. The length of the capillary tube, the on/off temperature and the mounting dimensions must match. Universal models exist, but require precise adjustment.
The process of replacing a mechanical sensor takes about 30-40 minutes. It is necessary to carefully pull the old tube out of the evaporator so as not to damage the aluminum channels. A new tube is inserted to the same depth. Excessive immersion or, conversely, a short tube will lead to incorrect temperature readings.
Sequence of actions:
- Remove the old regulator, remembering the wiring diagram (it is better to take a photo).
- Install the new unit in place, secure with screws.
- Carefully straighten the capillary tube inside the chamber, avoiding kinks.
- Connect the wires according to the diagram.
- Turn on the refrigerator and check the operation in test mode.
⚠️ Attention: The capillary tube is very thin and fragile. Do not bend it at a sharp angle or jerk it sharply. Damage to the tube will result in a gas leak and the thermostat will stop working permanently.
Adjustment may be required after installing a new element. There is often a screw on the case, the rotation of which shifts the temperature range. This should be done with a small screwdriver, turning the screw literally a fraction of a turn, and waiting for the temperature to stabilize for several hours.
Frequently asked questions (FAQ)
Is it possible to temporarily short-circuit the thermostat to make the refrigerator work?
Yes, technically this is possible. If you connect the wires coming from the thermostat to the compressor, the motor will run constantly. However, this method cannot be used for a long time: the evaporator will become covered with ice, the food in the refrigerator compartment will spoil, and the compressor may burn out from overheating. This solution is only for emergency rescue of food for a couple of hours.
Why did the refrigerator begin to freeze more after replacing the thermostat?
Probably, the installed regulator has different temperature thresholds. It is also possible that the capillary tube is not immersed deep enough or, conversely, touches the chamber wall. Try turning the adjusting screw towards decreasing the cold.
How often should you change the thermostat?
The service life of a mechanical thermostat is on average 5-7 years. Electronic sensors last longer, but can fail due to power surges. Scheduled replacement is not required; change only when signs of malfunction appear.
Does the temperature in the room affect the operation of the thermostat?
Yes, it does. Most household refrigerators are designed to operate in climate class SN-N (from +10 to +32°C). If the room is colder than +10°C, the thermostat may not turn on the compressor, thinking that it is already cold inside. If it is hotter than +32°C, it will work at its maximum capacity.