The main element that ensures stable The operation of the cooling system in household appliances is the thermostat. It is this small component that controls the cycles of turning the compressor on and off, maintaining a given temperature regime inside the chambers. Without its correct operation, the refrigerator would turn into an ordinary cabinet, unable to keep food fresh for a long time.
Understanding this what the thermostat is responsible forallows owners of household appliances to independently diagnose many common problems. Often it is malfunctions in the operation of this unit that lead to food spoilage or excessive energy consumption. In this article we will analyze in detail the structure of the mechanism, its role in the overall system and methods for checking serviceability.
Modern models of refrigerators can be equipped with both mechanical and electronic regulators. The principle of their operation is similar, but the design and diagnostic methods differ significantly. Let's look at how exactly the temperature is controlled in your unit.
The main function and principle of operation of the thermostat
The main task of the thermostat is to automatically open and close the electrical power circuit of the compressor depending on the temperature in the evaporator. When the air inside the chamber cools to the set value, the contacts open and the motor stops. As the temperature rises, the process is repeated in the reverse order.
The mechanical one is based on a bellows tube filled with freon or other substitute gas. This tube is pressed tightly against the evaporator. When the temperature changes, the gas inside the tube contracts or expands, affecting the membrane, which, in turn, opens or closes the contact group. This is a simple but effective mechanism. thermostat lies a bellows tube filled with freon or other substitute gas. This tube is pressed tightly against the evaporator. When the temperature changes, the gas inside the tube contracts or expands, affecting the membrane, which, in turn, opens or closes the contact group. This is a simple but effective mechanism.
Electronic analogues work differently: they use thermistors, the resistance of which changes depending on the heating. The signal is transmitted to the main control module, which makes the decision to start the compressor. Such systems provide more accurate temperature control, but are more difficult to diagnose.
It is important to note that in In two-chamber models, the sensor usually monitors the temperature in only one chamber, most often the refrigerator. The freezer compartment is cooled according to the residual principle or through a separate circuit, but the control element is still the main thermostat.
Design and location of the temperature sensor
The location of the thermostat depends on the model of the refrigerator and the type of control. In classic models with a top freezer and mechanical controls, the regulator is often located inside the refrigerator compartment. In this case, the control handle is built into the lampshade or placed on the inner wall.
In models with a system No Frost or electronic control, the control unit can be placed outside, on the upper part of the refrigerator body. In this case, only the sensitive element - a capillary tube or thermistor wires - leads to the evaporator. Access to it often requires partial disassembly of the internal panel.
Structurally, the device consists of several key elements:
- 🔹 Sensing element —a capillary tube or thermistor that is in direct contact with the cooled object.
- 🔹 Actuator —a contact group that opens the power circuit compressor.
- 🔹 Adjusting screw —allows the user to change the contact temperature range.
- 🔹 Housing —protects internal parts from moisture and mechanical damage.
Why is the capillary tube so long?
The length of the tube (usually 0.5 - 2.5 meters) is necessary so that the sensing element can be brought from the adjustment knob, located outside or at the top, directly to the evaporator, which can be located at the bottom of the chamber or behind the back wall.
When replacing a part, it is critical to consider the length capillary tube. If the new part has a tube shorter than the standard one, it may not be enough for proper placement in the evaporator, which will lead to incorrect operation of the entire system.
Symptoms of a malfunctioning thermostat
You can determine that it is the one that has failed refrigerator thermostatby a number of characteristic signs. Most often, a breakdown manifests itself in a violation of the temperature regime or a change in the operating mode of the compressor.
One of the most obvious symptoms is that the refrigerator has stopped turning off. The compressor runs continuously and hums, but the temperature inside the chambers can be either normal or extremely low. This indicates that the contacts are “stuck” in a closed state, and the stop command is not received.
The opposite situation is that the unit does not turn on at all. In this case, the compressor is silent, there is no light in the chamber (if it is powered through a thermostat) or it is constantly on, but there is no cold. The contacts are broken and do not close even when the temperature rises.
You should also pay attention to the following signs:
- ❄️ Food in the refrigerator compartment freezes, although the regulator is turned to minimum.
- 🌡️ The temperature in the chambers is higher than normal, despite the maximum cold setting.
- ⚡ Electricity consumption has increased sharply due to the continuous operation of the motor.
- 🔊 The compressor makes clicks when trying to start, but the start itself does not occur.
In some cases, the thermostat may not work correctly, causing it to turn on too frequently and turning off the engine. This phenomenon is called a “short cycle” and has an extremely negative impact on the life of the compressor.
Diagnostics and checking the serviceability of the part
Before buying a new part, you need to make sure that it is faulty. Self-diagnosis of the thermostat is possible using a multimeter. To do this, you will need to remove the device body and get to the contact group.
The test process is as follows:
- De-energize the refrigerator by removing the plug from the socket.
- Remove the regulator handle and dismantle the thermostat housing.
- Disconnect the wires from the contacts (first take a photo of the connection diagram).
- Set the multimeter in continuity or resistance measurement mode.
- At room temperature, the contacts should be closed (resistance is close to zero).
☑️ Algorithm for checking the thermostat
For a more accurate check, you can place the sensitive tube in a container with ice water. In a working mechanical thermostat, when cooled to a certain temperature (usually about 0...+5°C), a click should be heard and the circuit will open. If this does not happen, the part must be replaced.
It is worth considering that in electronic models, testing with a multimeter shows only the integrity of the circuit, but not the operation of the logic. To diagnose electronic thermistors, knowledge of their nominal resistance at different temperatures is often required, which can be found in the technical documentation.
Comparison of mechanical and electronic thermostats
The choice between mechanics and electronics affects not only ease of use, but also the maintainability of the device. Mechanical thermostats, such as TAM-133 or K-59are simple and reliable. They are less likely to fail due to power surges and are easily replaced.
Electronic control modules provide more stable temperatures, eliminating fluctuations characteristic of mechanics. However, they are sensitive to power surges and require more complex diagnostics. Often, a breakdown of the electronic thermostat requires replacement of the entire control unit.
| Characteristics | Mechanical thermostat | Electronic module |
|---|---|---|
| Maintenance accuracy | ±2-3°C | ±0.5-1°C |
| Resistance to horse racing | High | Low (stabilizer needed) |
| Replacement cost | Low | High |
| Diagnosis complexity | Minimal | Requires equipment |
In modern premium refrigerators, mechanics are practically not used. At the same time, in budget models and older series it remains a standard due to its low cost and versatility.
Replacing the thermostat with your own hands
If diagnostics have confirmed a malfunction, you can replace it yourself. This is a procedure of medium complexity, requiring accuracy and a minimum set of tools. The main rule is safety, so work is carried out only when the device is disconnected from the network.
First you need to remove the old thermostat. In models where it is located inside the chamber, you need to remove the plastic casing, unscrew the fastener and carefully pull the capillary tube out of the evaporator. Be careful: the tube is very thin and is easily pinched or bursts.
What to do if the new tube is longer than the old one?
Under no circumstances should excess capillary tube be cut off! They must be carefully rolled into a ring (with a diameter of at least 5 cm) and placed inside the case or behind the back wall, being careful not to damage the insulation.
Installation of the new part is carried out in the reverse order. It is important to properly secure the sensing element to the evaporator using standard pressure plates. Insufficient contact will result in the refrigerator “lying” about the temperature inside.
After assembling and turning on the refrigerator, you need to let it work for several hours without loading food. This will allow the system to enter operating mode and ensure that the new thermostat operates correctly.
Frequently asked questions and answers
Is it possible to temporarily short-circuit the thermostat to does the refrigerator work?
Technically this is possible: connecting the wires directly will make the compressor work constantly. However, this can only be done briefly to check the compressor or in an emergency for a couple of hours. Long-term operation without a thermostat will lead to freezing of food and icing of the evaporator, as well as overloading the engine.
Why does the refrigerator click but does not turn on?
Clicks can be made by both the thermostat contacts when trying to close, and the thermal compressor protection relay. If clicks occur at intervals of several minutes, but there is no cold, the problem may be in the start relay, the compressor itself, or a lack of contact in the thermostat circuit.
How often should the thermostat be changed?
The thermostat does not have a strict service life. Mechanical models last 5-10 years or more. Replacement is made only upon failure. Preventative replacement is not required if the device works correctly and maintains the temperature.
Does the temperature in the room affect the operation of the thermostat?
Yes, mechanical thermostats are sensitive to ambient temperature. If the room is very cold (below +10°C), the refrigerator may not turn on at all, since the sensor “thinks” that it is already cold inside. For such conditions, there are special models with heated thermostat zone.
⚠️ Attention: The capillary tube of the thermostat is filled with gas under pressure. It is strictly forbidden to bend it at an acute angle, pierce it or heat it with open fire. Damage to the tube makes the part unsuitable for repair, and the gas can be flammable.