The question of what exactly is called thermometer in the refrigeratoroften arises among owners of household appliances who are faced with unstable operation of the unit or desire to make an accurate diagnosis. In everyday life, we are used to using simple names, but technical documentation and service engineers use more complex terms. Understanding the difference between an external measuring device and an internal control sensor is the first step to competent operation and successful repair.
If we talk about an external device, which you can buy separately and put on a shelf to check the temperature regime, then it is simple household thermometer or temperature meter. However, if you are interested in a part built into the structure of the refrigeration chamber and responsible for automatically adjusting the cold, then a more complex nomenclature comes into force. Most often this element is called thermostat or temperature sensor, although technically these concepts have significant differences in the principle of operation and design.
It is important to immediately note that confusion in the names can lead to errors when ordering spare parts. The mechanical regulator, which makes a clicking sound when the compressor is turned on, and the electronic sensor, which transmits data to the control board, are different devices. Next, we'll take a closer look at how to correctly identify these elements, how they differ, and why knowing the exact name is critical to maintaining the freshness of your products.
Thermostat: the mechanical heart of an old refrigerator
In classic refrigerator models, where control is carried out by a rotary knob with numbers from 1 to 7, the main control element is thermostat. This is a mechanical device that physically opens and closes the electrical circuit of the compressor depending on the temperature of the evaporator or the air in the chamber. Inside such a device there is a bellows tube filled with a sensitive gas (freon), which expands when heated and contracts when cooled, transferring pressure to the contacts.
It is the thermostat that is responsible for maintaining a given temperature range. When you turn the handle, you mechanically change the tension of the spring, setting the force that the gas must develop in the bellows to open the contacts. If the thermostat fails, the refrigerator may either stop turning on or run nonstop, turning the compartment into a freezer. Replacing this unit requires precise selection of the model, since the length of the capillary tube and the temperature response range may differ from one manufacturer to another.
⚠️ Attention: When replacing the thermostat yourself, it is critically important to correctly install the sensitive tube. If it is not pressed tightly enough to the evaporator or is accidentally pinched, the refrigerator will not work correctly, and food may spoil.
Modern electronic systems are gradually replacing mechanics, but thermostats are still widely used due to their reliability and low cost. They do not require complex electronics and can operate even during power surges that would damage sensitive microprocessors. However, their accuracy is lower than that of their electronic counterparts, and they are not able to control additional functions such as No Frost or a freshness zone.
Electronic sensors: thermistors and their role
In new generation refrigerators equipped with a digital display and control buttons, the function of a thermometer is performed thermistors. These are semiconductor elements whose resistance varies depending on the ambient temperature. Unlike mechanical thermostats, they do not open the compressor power supply circuit directly, but only send a signal to control module (electronic board), which already makes the decision to turn the motor on or off.
Main advantage Thermistors are characterized by high measurement accuracy and the ability to flexibly configure operating algorithms. The control board can analyze the readings of several sensors simultaneously: in the refrigerator compartment, in the freezer, on the evaporator and even in the freshness zone. This allows complex functions such as super freeze, holiday mode or intelligent cold distribution to be implemented. If one of the sensors fails, the system often goes into emergency mode and signals the error by flashing indicators.
There are two main types of thermistors used in refrigeration technology:
- ❄️ NTC (Negative Temperature Coefficient): The resistance drops as the temperature rises. This is the most common type in household appliances.
- 🔥 PTC (Positive Temperature Coefficient): Resistance increases with increasing temperature. It occurs less frequently, mainly in specific protection systems.
Diagnostics of the electronic sensor is usually carried out using a multimeter in resistance measurement mode. Knowing the characteristics of a particular model (often this is tabular data from the manufacturer), the technician can determine whether the element is working. Replacing a thermistor is usually easier than replacing a mechanical thermostat, since it does not require adjustment of a long capillary tube, but requires care when working with electronic connectors.
Why do sensors fail?
The main reason for thermistor failure is the natural aging of the semiconductor material and exposure to moisture. Condensation that gets onto the contacts or inside the sensor housing can cause oxidation and change the electrical resistance, which leads to distorted readings. Also, the sensors may suffer from mechanical damage when defrosting ice with sharp objects.
Differences between a thermostat and a temperature sensor
Many users mistakenly believe that a thermostat and a temperature sensor are synonyms. Although their temperature control function is similar, they are structurally and functionally different devices. Understanding this difference is necessary for properly searching for spare parts and communicating with a service engineer. Confusion in terms can lead to the purchase of an unsuitable part that cannot be installed.
For a visual comparison of characteristics, consider the following parameters:
| Parameter | Thermostat (Mechanical) | Thermal sensor (Electronic) |
|---|---|---|
| Principle of operation | Physical expansion of gas in the bellows | Change in electrical resistance |
| Control | Direct opening of the compressor circuit | Signal transmission to the board controls |
| Accuracy | Low (error 2-3°C) | High (error 0.5-1°C) |
| Adjustment | Mechanical handle on case | Electronic panel or application |
| Add. functions | Absent | Super freezing, self-diagnosis |
Thermostats can most often be found in budget models or refrigerators released more than 10-15 years ago. Their design is simple and reliable, but they do not provide the level of comfort and precision that modern electronic systems provide. Electronic sensors, in turn, make the refrigerator “smart”, but make it more sensitive to voltage drops and power surges.
If your refrigerator begins to act up, pay attention to the nature of the malfunction. Sharp clicks and lack of cold often indicate problems with the thermostat. Random switching on, errors on the display or lack of response to changing temperature settings are sure signs of problems with thermal sensor or the control board. In any case, for an accurate diagnosis it is better to call a specialist.
External measuring instruments for testing
When it comes to checking the temperature inside the refrigerator, users often ask the question: “Which thermometer should I put in the refrigerator?” The built-in indicators on the door or display only show approximate values or air temperature at the outlet of the duct, but not the actual temperature of the food. For accurate diagnostics, it is recommended to use an external measuring device.
There are several types of external thermometers that are ideal for this task:
- 🌡️ Analogue alcohol thermometers: Classic version that does not require batteries. Ideal for long-term monitoring, as they show the current temperature in real time without delay.
- 📱 Digital thermometers with a remote probe: Allow you to display the display outside without opening the door. This prevents warm air from getting inside while taking readings.
- 🔫 Infrared pyrometers: They allow you to measure the surface temperature of products or shelves instantly, but are not suitable for measuring the air temperature inside the chamber.
The use of an external thermometer is especially important if you notice that food is spoiling faster than usual or, conversely, is freezing in the refrigerator compartment. The normal temperature for the refrigerator compartment is considered to be from +2°C to +5°C, and for the freezer - -18°C and below. Regular measurements will help you notice deviations in time and contact service before the problem becomes critical.
When choosing a device, give preference to models with a measurement range from -30°C to +50°C. Conventional room thermometers may not provide correct readings at low freezer temperatures. It is also important to place the thermometer in a glass of water or between packages of food, and not on an empty shelf, in order to get an average temperature of the contents, not just the air.
Typical malfunctions and their symptoms
Problems with temperature control are one of the most common reasons for contacting service centers. Symptoms can range from subtle abnormalities to complete equipment failure. Understanding how a faulty one behaves will help you quickly navigate the situation. thermostat, will help you quickly navigate the situation.
The most common signs of failure:
- The refrigerator does not turn on: The compressor is silent, the light inside is on. This may mean that the thermostat contacts have oxidized and do not complete the circuit, or the electronic sensor transmits a false signal that the temperature is already quite low.
- The refrigerator works without stopping: The motor hums around the clock, a “fur coat” forms in the chamber, and the food freezes. The thermostat is “stuck” in the “on” position or the temperature sensor shows incorrect data (for example, that the chamber is +20°C, although it is already -5°C).
- Frequent switching on and off: The operating cycle becomes too short. This may indicate incorrect calibration or partial malfunction of the sensitive element.
⚠️ Attention: If your refrigerator starts working continuously, this not only threatens the safety of the food, but can also lead to overheating and combustion of the compressor. Do not ignore the first signs of a malfunction in the temperature control.
Sometimes the problem lies not in the sensor or thermostat itself, but in a leak in the chamber, a freon leak, or a fan malfunction. However, it is the temperature control system that is often the first to respond to these changes, trying to compensate for the loss of cold by continuously running the engine. Therefore, diagnostics always begin with checking the sensor readings.
In electronic models, the system itself often reports a sensor malfunction. Error codes (for example, E1, F2 or flashing temperature indicators) may appear on the display. The decoding of the codes can be found in the instructions for your model or on specialized forums. In mechanical models, you have to guess about the problem only by indirect signs - the temperature of the food and the operation of the compressor.
☑️ Diagnosis of the problem
FAQ: Frequently asked questions
Is it possible to replace a mechanical thermostat to an electronic sensor?
As a rule, such a replacement is impossible without serious modification of the design. A mechanical thermostat controls the 220V circuit directly, but an electronic sensor needs a control board that will process its signal. A simple one-to-one replacement will not work, since they have different principles of operation and fastening.
Why does the built-in thermometer on the door show a temperature different from the real one?
Built-in indicators often show not the current air temperature, but a user-specified mode or an average value. In addition, the sensor located in the door is affected by warm air when opening, so its readings are less accurate than measurements inside the chamber.
How often should the thermostat or temperature sensor be replaced?
These parts do not have a strict expiration date. They serve until they fail, which can happen after 5 years, or maybe after 15. Preventative replacement is not required if the refrigerator is working properly and maintains the temperature.
Does the location of the thermostat affect its operation?
Yes, critically. The sensitive tube of the mechanical thermostat must be tightly secured in a special socket on the evaporator. If it dangles or is displaced, the refrigerator will “lie” about the temperature in the chamber, which will lead to incorrect switching cycles.