A sudden breakdown of the refrigerator is always stressful, especially when food begins to melt in the chamber, and the compressor either works without stopping or is silent. In most cases, if the unit no longer maintains the set temperature, the culprit becomes thermostat. This small but critical element is responsible for turning the motor on and off depending on the temperature inside the chamber.
Many owners of household appliances make the mistake of trying to buy the first part they come across with a similar name, not realizing that thermostats they can differ radically in design and electrical parameters. The wrong choice will lead to the fact that the refrigerator either will not start or will work in emergency mode, which will quickly damage the compressor.
In this article we will look in detail at how to determine the fault in the sensor, what parameters must be taken into account when selecting an analogue and how not to get confused in the markings of various manufacturers. Understanding the principles of operation thermostat will help you save time on searching and avoid repeated breakdowns.
Principle of operation and signs of malfunction of the thermostat
Thermostat is an electromechanical or electronic device that controls the temperature in the refrigerator compartment. Classic models use a capillary tube filled with refrigerant that responds to changes in thermal expansion. When the temperature rises above a preset threshold, the contacts close, starting the compressor.
If you notice that your refrigerator has begun to behave inappropriately, it is worth checking the condition of the sensor. Often, users confuse a breakdown of the thermostat with a freon leak or a malfunction of the start relay, which leads to unnecessary expenses for diagnostics.
Pay attention to the following symptoms, which are highly likely to indicate a problem with thermostat:
- ❄️ The compressor works continuously without turning off, and a “snow coat” forms in the chamber.
- 🔇 The motor does not start at all, although the light inside is on and the network is working properly.
- 🌡️ The temperature in the chamber differs significantly from that set on the regulator (too high or too low).
It is worth noting that in modern models with a system No Frost and electronic control, the thermostat function is often performed by a thermistor (electronic resistance sensor). Checking it requires a multimeter and knowledge of resistance values, while mechanical analogues can be checked using simpler methods.
Types of thermostats: mechanical versus electronic
The first thing you need to decide before purchasing is the type of control of your refrigerator. Not only the price of the part depends on this, but also the complexity of its installation. Mechanical thermostats are still found in budget models and old-style appliances.
They are distinguished by their reliability and simplicity of design. Inside such a device is a bellows that contracts or expands under the influence of temperature, opening or closing an electrical circuit. Replacement such a part usually does not require complex soldering or programming.
⚠️ Attention: When installing a mechanical thermostat, it is critically important to correctly position capillary tube. If it touches the walls of the chamber or is not secured correctly, the temperature readings will be distorted, which will lead to frequent starts of the motor.
Electronic thermostats (thermistors) are resistors that change their resistance depending on the temperature. They are installed in models with digital control. Such sensors are often paired with the main control module, and their replacement may require resetting errors in the controller's memory.
Visually it is easy to distinguish them: a mechanical thermostat has a rotary knob with divisions (from 1 to 7 or Min/Max), and an electronic one is controlled through a panel with display or hidden buttons. Purchasing the wrong type of sensor will make repairs impossible without completely replacing the control unit.
Markings and compatibility: how to read codes
The most reliable way to choose the right thermostat is to rely on the factory markings. Manufacturers use a unified coding system that informs the master about the length of the capillary tube, temperature range and type of contacts.
The most common thermostats are from Tamato (formerly Ranco), which are installed in refrigerators Indesit, Ariston, Stinol and many others. Their markings look like a set of letters and numbers, for example, K59-L1275. Let's figure out what this means.
The first letter or combination of letters indicates the temperature regime. For example, the series K59 is designed for single-chamber refrigerators or the fridge compartment of two-chamber models. Series K50 or K56 is more often used for freezers.
The numbers after the hyphen indicate the length of the capillary tube. In the example of L1275, the number 1275 means a length of 1275 mm (1.27 meters). If you buy a thermostat with a shorter tube, it simply will not reach the desired place in the chamber, and one that is too long will have to be carefully placed so as not to damage it.
Below is a table of common markings and their compatibility with brands:
| Marking | Chamber type | Tube length (mm) | Compatible brands |
|---|---|---|---|
| K59-L1275 | Refrigeration | 1275 | Indesit, Ariston, Stinol |
| K50-L1950 | Freezer | 1950 | Atlant, Biryusa |
| TAM-133 | Refrigeration | 0.73 m | Biryusa, Oka, ZIL |
| K-57-L1450 | Refrigeration | 1450 | LG, Samsung (mechanical) |
It is important to understand that compatibility is determined not only by the brand of the refrigerator, but also by the specific model. The same manufacturer can use different thermostats in different series of equipment.
Is it possible to use a thermostat with a different tube length?
Theoretically, it is possible if the new thermostat has a tube longer than the original. The excess part can be carefully rolled into a ring and secured inside the housing without bending the tube. However, it is absolutely impossible to use a thermostat with a shorter tube - the sensor will not correctly read the temperature in the desired zone.
Length of the capillary tube: a critical parameter
The length of the capillary tube is perhaps the most important geometric parameter when choosing an analogue. It determines how deeply the sensitive element can be immersed in the refrigeration chamber or evaporator.
Standard sizes range from 0.5 meters to 2.5 meters. If the tube is too short, you will physically not be able to install the thermostat in its original place. In some cases, craftsmen try to “extend” the tube, but this is prohibitedwill break the tightness of the system and lead to leakage of the working gas.
When purchasing, pay attention to the configuration of the tube. In some models it may have a specific bend or thickening at the end. The response temperature is also important, which depends on the calibration of the bellows inside the housing.
☑️ Check before purchasing a thermostat
If you cannot find an exact copy in length, always choose a thermostat with a margin. Excess length can be easily compensated by carefully folding the tube in the free space behind the back wall or in a special channel without violating its integrity.
Features of choice for different brands
Different manufacturers of refrigeration equipment have their own preferences in components. Knowing these nuances will help you narrow down your search and avoid buying the wrong part.
For refrigerators Atlant and Biryusa thermostats of the K-50 or TAM-133series are most often used. A special feature of these models is the frequent fastening through a special nut and the presence of a grounding jumper, which cannot be ignored during installation.
Technique Indesit i Ariston traditionally equipped with products Ranco (now Emerson). It is important to pay attention to the position of the contacts here. In some models, they may be offset relative to the axis of the body, which will require careful adjustment during installation.
⚠️ Attention: In refrigerators with two compressors (separately for the freezer and refrigerator compartment), different thermostats are used. Do not confuse them: the sensor for the freezer is designed for lower response temperatures.
In modern refrigerators Samsung and LG mechanical thermostats are less common, but if your model belongs to a series 10-15 years ago, there may be specific sensors with a short tube and a special connector. For them, it is better to look for original spare parts by model code.
Instructions for replacement and initial setup
After you have selected and purchased the correct thermostat, you need to install it correctly. The process requires care and compliance with safety precautions. Before starting work, be sure to disconnect the refrigerator from the power supply.
Remove the old thermostat by carefully pulling the capillary tube out of the evaporator. Do not use excessive force to avoid damaging the thin-walled evaporator. Install the new sensor, placing the tube at the same depth as the previous one.
After connecting the electrical contacts and assembling the housing, it is necessary to carry out the initial setup. Set the control knob to the middle position (usually number 3 or 4). Start the refrigerator and let it run for 2-3 hours.
Check the temperature in the chamber using an external thermometer. If it is not within the standard, perform calibration. On the body of many thermostats there is an adjusting screw, turning which half a turn changes the response temperature by 1-2 degrees.
Frequently asked questions (FAQ)
Is it possible to temporarily do without a thermostat by connecting the refrigerator directly?
Technically, you can start the compressor directly, but this is an emergency mode. The refrigerator will operate continuously, which will lead to deep freezing of food, icing of the evaporator and, ultimately, to overheating and combustion of the motor-compressor. Use this method only for a short-term check of the operation of the compressor itself.
Why does the new thermostat click, but the refrigerator does not turn on?
The click means that the contacts open and close, but no current flows. Possible reasons: oxidation of the contacts inside the thermostat itself (defective or long-term storage), incorrect connection of the wires (phase and neutral are reversed if there is grounding) or a malfunction of the compressor starting relay, which often fails simultaneously with the thermostat due to power surges.
How to distinguish a high-quality analogue from a fake?
Quality thermostats (for example, Ranco, Danfoss, Tamato) have clear, indelible laser markings, neat plastic or metal stamping of the body and reliable contacts. Counterfeits are often characterized by play in the adjustment knob, blurred printing, and the light weight of the case made of cheap plastic.
Do you need to defrost the refrigerator before replacing the thermostat?
Complete defrosting is not necessary if you act quickly. However, if there is a lot of ice in the chamber, it is better to wait until it melts so that water does not get on the electrical contacts of the new thermostat or in the wiring. Moisture can cause a short circuit when turned on for the first time.