A sudden stop of operation of the refrigerator or, conversely, its endless operation without shutting down often indicates a malfunction of the temperature control system. In two-chamber models of the brand Atlant the thermostat, which is one of the most loaded elements of the electrical circuit, is responsible for this process. Understanding the principle of its operation will help the owner independently diagnose the problem and avoid an expensive call to a technician to simply replace the part.
The thermostat functions as a “brain” that analyzes the temperature inside the refrigeration chamber and sends a command to the compressor to turn on or off. If this mechanism fails, the entire refrigeration cycle is disrupted, which can lead to food spoilage or freezing of the evaporator. In this article, we will analyze in detail the internal structure of the device, its electrical characteristics and troubleshooting algorithms.
For accurate diagnostics, you do not need complex laboratory equipment, just a basic set of tools and a multimeter. We will look at the differences between mechanical and electronic regulators that are found in different series of equipment Atlant, and explain why replacing one element can solve the problem of a “warm” refrigerator.
⚠️ Attention: Before starting any work on disassembling the refrigerator, be sure to disconnect the device from the electrical network. Working with live electrical wiring is strictly prohibited and is dangerous to life.
Design and principle of operation of a mechanical thermostat
The basis of a classic thermostat is a sealed system filled with a temperature-sensitive gas or liquid. In refrigerators Atlant most often, models of the TAM or K-59 series are used, where the working medium is enclosed in a long capillary tube, the end of which is attached to the evaporator inside the chamber. When the temperature changes, the refrigerant inside the tube expands or contracts, transferring pressure to the bellows.
The bellows, in turn, acts on the moving contact, closing or opening the electrical circuit of the compressor. When you turn the adjustment knob, you mechanically change the spring tension, setting the threshold for the contacts to operate. This is a simple but reliable mechanism, which, however, can wear out over time, losing its elasticity or tightness.
It is important to understand that the thermostat does not respond to the temperature of the air in the chamber as a whole, but to the temperature of a specific attachment point of the capillary tube. That is why incorrect installation of the sensor after repair can lead to incorrect operation of the entire unit. Mechanical models are considered more maintainable and cheaper to maintain compared to their electronic counterparts.
Why do thermostats fail?
The main cause of failure is depressurization of the bellows or capillary tube. Also, the contacts inside the device can burn due to frequent switching, which leads to sticking or, conversely, lack of contact.
Electronic thermostats in modern models
Modern refrigerators Atlant with a system No Frost or improved design often equipped with electronic control modules. In such devices, the role of a mechanical tube is performed by temperature sensors (thermistors), the resistance of which varies depending on the temperature. The signal from the sensor is sent to the main control unit, which programmatically makes a decision to start the compressor.
The advantage of the electronic system is the high accuracy of maintaining the temperature and the ability to display current indicators on the display. However, diagnosing such systems requires the use of a multimeter to measure the resistance of the sensor, since it is impossible to visually determine its malfunction. Often the problem lies not in the sensor itself, but in oxidation of the loop contacts or failures in the control board.
When replacing an electronic thermostat, it is important to observe the connection polarity and use original components, since analogues may have a different resistance curve. This will cause the refrigerator to not work correctly, even if the new part is working properly. Electronics are more sensitive to voltage surges, so it is recommended to use a stabilizer for protection.
Typical symptoms of a malfunctioning thermostat
You can determine that it is the thermostat that has failed by the characteristic signs of the operation of the refrigeration equipment. Most often, owners are faced with a situation where the compressor runs continuously without turning off for hours, and the freezer becomes covered with a “fur coat,” and the food in the refrigerator compartment freezes. This indicates that the regulator contacts are “stuck” in the closed state.
The opposite situation, when the refrigerator is silent and does not respond to turns of the adjustment knob, also indicates a problem with the thermostat. In this case, the circuit is broken and there is no signal to start the engine. Sometimes the refrigerator may turn on, but work in very short cycles, which is also a sign of incorrect calibration or breakdown.
- 🧊 The compressor hums constantly, without taking a break, and the temperature in the chamber drops below 0°C.
- 🔌 The refrigerator is completely silent, the indicators are on, but the engine does not start even at minimum setting.
- 🌡️ The temperature in the refrigerator compartment is unstable: the food either thaws or becomes covered with frost without changing the settings.
It is worth noting that similar symptoms may appear when there is a freon leak or a compressor malfunction. Therefore, before replacing the thermostat, it is necessary to exclude other causes. For example, if the compressor is hot, but there is no cold, most likely the problem is in the refrigerant, and not in the electrics.
Dismantling and visual inspection of the part
To access the thermostat in refrigerators Atlant usually you need to remove the plastic cover that hides the lighting lamp and temperature controller. In some models, the handle is simply removed by hand, in others you need to unscrew the fastening screw. After removing the decorative panel, access to the thermostat body becomes available.
Carefully disconnect the terminals with wires, having previously memorized or photographed their location. The thermostat is attached to the refrigerator body with screws or latches. The capillary tube must be removed from the chamber very carefully so as not to damage its thin walls. Any microcrack will lead to failure of the new part immediately after installation.
During a visual inspection, pay attention to the condition of the contacts: if they are blackened or melted, the thermostat definitely requires replacement. Also check the integrity of the wire insulation. If the capillary tube is swollen or has signs of corrosion, this is a sign of depressurization of the internal system.
⚠️ Attention: The capillary tube of the thermostat is filled with gas under pressure. Do not try to repair it, solder it or heat it with an open fire - this may lead to an explosion or the release of harmful substances.
Checking the thermostat with a multimeter
The most accurate diagnostic method is to “test” the contacts using a multimeter. To do this, the device is switched to resistance measurement or circuit continuity testing mode. The probes are connected to the thermostat contacts, after which you need to manually change the temperature of the sensor.
Immerse the capillary tube (or the entire thermostat, if the design allows) in a container with water at room temperature (+18..+20°C). In this state, the contacts should be closed and the multimeter should read zero or beep. Then put the tube in ice water (about 0..+5°C). If the thermostat is working properly, when it cools down it should click and break the circuit - the multimeter will show infinity.
If there is no click when cooling and the circuit does not break, it means that the mechanism is jammed or the seal of the bellows is broken. If the circuit does not close even in warm conditions, the contacts are burnt or oxidized. In both cases, the part must be recycled and replaced.
☑️ Checking the thermostat with a multimeter
Standard values for the refrigerator compartment are usually in the range from +3 to +10°C. Using universal tables may result in errors, so it is better to focus on the behavior of a specific part.
Instructions for replacing and setting up a new thermostat
Installing a new regulator is done in the reverse order of dismantling. The capillary tube must be carefully inserted into the mounting hole and secured in its proper place on the evaporator. It is important to ensure tight contact of the tube with the surface of the evaporator; often a special clamping strip or thermal paste is used for this.
After connecting the electrical terminals and assembling the plastic panels, you can turn on the refrigerator to the network. It is recommended to perform the first setup with an empty chamber. Set the regulator knob to the middle position (usually number 3 or 4) and let the unit operate for several hours.
To fine-tune the temperature inside the chamber, you can use an external thermometer placed in a glass of water. Achieve stable readings of +4..+6°C by turning the thermostat knob. If the refrigerator has a system No Frost, make sure that the defrost cycle is also working correctly.
| Parameter | Normal value | Tolerable deviation |
|---|---|---|
| Temperature in HC | +4°C.. +6°C | ±2°C |
| Opening temperature | +3°C.. +5°C | ±1.5°C |
| On temperature | +10°C.. +12°C | ±2°C |
| Resistance (20°C) | 0 Ohm (closed) | 0.1 Ohm |
Is it possible to temporarily close the thermostat to make the refrigerator work?
Technically, you can close the thermostat contacts by connecting the wires directly. In this case, the compressor will operate continuously. However, this is an emergency measure: without temperature control, food in the refrigerator compartment will freeze, and the compressor may burn out from overload or lack of rest cycles. This method can only be used for short-term defrosting or checking the compressor.
Why does the new thermostat not fit?
Refrigerators Atlant there are many modifications, and thermostats may differ in the length of the capillary tube, thread diameter and contact location. If the tube is too long, you can carefully twist it into a ring and place it inside the housing, but do not cut it under any circumstances. If the threads do not match, you may need an adapter or replacement of the mounting strip.
How often should you change the thermostat in the refrigerator?
The service life of a mechanical thermostat is on average 5-7 years of active use. However, with frequent power surges or regular overloads of the refrigerator (loading warm food), the service life may be reduced to 3 years. Planned preventative replacement is not required - they are replaced only when symptoms of a malfunction appear.
Does the amount of freon in the system affect the operation of the thermostat?
Indirectly - yes. If there is little freon in the system, the evaporator will not cool to the desired temperature, and the thermostat may not work to turn off the compressor, since it “feels” the heat. As a result, the refrigerator will work without stopping. Therefore, before replacing the thermostat if the symptom “does not turn off,” always check the uniform cooling of the evaporator.
What to do if, after replacement, the refrigerator starts to turn on frequently?
Frequent turning on (short operating cycle) may be caused by incorrect adjustment of the differential of the new thermostat. Try changing the position of the adjustment knob. If the problem persists, it is possible that a thermostat is installed with the wrong temperature range for your model Atlant, or the capillary tube is not pressed tightly enough to the evaporator.