A modern refrigerator is a complex system where each element performs its own function, but it is the temperature regulator (thermostat) that acts as the main controller. It is he who decides when the compressor needs to start in order to cool the chambers, and when it should stop so as not to freeze the food. Understanding how this mechanism works will help you quickly diagnose a breakdown without calling a technician for a basic check, and extend the life of the unit.
The principle of operation is based on the physical expansion and contraction of substances when temperature changes. Inside the device there is a sensitive tube filled with refrigerant, which reacts to the slightest fluctuations in degrees in the fridge compartment. If you notice that your Indesit or Atlant started to idle or, conversely, turned food into ice, the problem most often lies in the calibration or failure of this sensor.
It is important to distinguish between mechanical regulators, which are controlled by a rotary knob, and electronic modules, where the temperature is set in numbers on display. In the first case, we are dealing with reliable mechanics that open the contacts, in the second, with software and electronic resistance sensors. In mechanical thermostats, the critical parameter is the length of the capillary tube, which should not be changed or damaged during installation.
Design features of a mechanical thermostat
Mechanical thermostat is a sealed system consisting of a bellows (accordion-shaped element) and a long capillary tube. This entire structure is filled with an inert gas or freon, which expands when heated, creating pressure on the bellows membrane. This pressure is transmitted to a lever mechanism, which physically opens the electrical contacts, stopping the compressor.
When the temperature inside the chamber rises, the gas in the tube is compressed, the pressure drops, and the spring returns the contacts to the closed position, starting the cooling cycle again. Reaction speed the system directly depends on the length tubes and heat transfer quality. If the tube is not pressed tightly enough to the evaporator, the sensor will “lie”, showing a higher temperature than it actually is.
The adjustment knob located inside the chamber or on the front panel changes the tension of the spring, which is responsible for the force of opening the contacts. By turning the knob, you do not change the temperature of the gas, but only set the force that the bellows must overcome. That is why there are often no degrees on the handles, but only symbols from “Min” to “Max” or numbers from 1 to 7.
⚠️ Attention: When replacing the thermostat yourself, it is strictly forbidden to bend the capillary tube at an acute angle or shorten it. Violation of the tightness or change in the volume of the tube will lead to complete inoperability of the regulator.
Modern models are often equipped with additional functions, such as “Quick freezing”. In this case, the regulator forcibly opens the contacts, preventing the compressor from turning off until you manually turn off this mode. This allows you to quickly freeze fresh food, but requires control so as not to burn the motor.
Why does the thermostat click?
When the mechanical regulator operates, you can hear a characteristic click. This is the sound of contacts opening or closing inside the bellows. If the clicks become too frequent or, on the contrary, disappear completely (with a change in temperature), this is a sign of wear of the contact group or loss of tightness of the system.
Electronic sensors and their difference from mechanics
In premium class refrigerators, such as Liebherr or Bosch s system No Frost, mechanics gave way to electronics. Here, instead of gas and bellows, thermistors (NTC sensors) are used, the resistance of which varies depending on the ambient temperature. The controller constantly reads these readings and makes a decision to start the compressor.
The main advantage of electronic systems is high accuracy. The error is only 0.5 degrees, while a mechanical analogue can “walk” by 2-3 degrees. In addition, the electronic module is capable of controlling not only the compressor, but also fans, defrosting heating elements and valves, creating a single intelligent network.
Diagnostics of such systems requires special equipment. If a mechanic can be “ring” with a regular indicator screwdriver or a multimeter for a short circuit, then to check the electronic sensor it is necessary to measure its resistance at different temperatures and check the data with the manufacturer’s table. Often the problem lies not in the sensor itself, but in the oxidized contacts of the control board.
Electronics are more sensitive to power surges in the network. A sharp jump can “kill” the controller, and the refrigerator will stop responding to any commands, even if the temperature sensor itself is intact. In such cases, a complex flashing or replacement of the control unit is required, which is almost impossible to do at home.
Symptoms of a malfunctioning temperature controller
You can understand that thermostat it has failed by a number of indirect signs that appear in the operation of the refrigerator. The most obvious symptom is that the compressor either runs continuously, humming and getting hot, or does not turn on at all, leaving the food warm. In both cases, the control circuit is broken or, conversely, short-circuited.
If the refrigerator starts to work “jerkily” (turns on for a minute, turns off for a minute), this may indicate sticking of the contacts inside the regulator. You should also be wary if a “coat” of ice has formed inside the chamber even with minimal settings, or, conversely, the products begin to deteriorate, although the knob is turned to the maximum.
Users often confuse a regulator breakdown with a freon leak or a compressor malfunction. To differentiate the problem, you can carry out a simple test: with the compressor running, jumper the thermostat contacts (after unplugging the refrigerator from the mains!). If the engine starts, then the problem is in the regulator. If not, look for the reason in the start relay or motor windings.
In electronic models, the refrigerator itself often signals a sensor malfunction by displaying an error code on the display. For example, this may be a code "21C" or "22C", 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. Samsung this may be a code "21C" or "22C" indicating a faulty refrigerator or freezer sensor. The decoding of the codes should always be found in the instructions for the specific model.
⚠️ Attention: If the compressor operates continuously for more than 12 hours, this can lead to its overheating and jamming. If such a symptom is detected, immediately disconnect the device from the network and call a technician for diagnostics.
Table of temperature conditions and settings
Correct setting of the regulator is the key to long life of products and energy savings. Many users do not know what the numbers on the regulator knob mean and set them randomly. Below is a table of correspondence between symbols and actual temperature conditions for most mechanical refrigerators.
| Handle position | Temperature range (°C) | Compressor operating mode | Recommendation |
|---|---|---|---|
| Min / 1 | +6...+8°C | Rare inclusions | Summer, small amount of products |
| Average / 3-4 | +2...+4°C | Normal cycle | Daily use (Optimal) |
| Max / 6-7 | 0...+1°C | Frequent on | Loading a large volume of products |
| Off | Room | Does not work | Defrosting or prolonged absence |
It is worth considering that the temperature in different zones refrigerator compartment may differ. The upper shelves are always warmer than the lower ones, next to the vegetable drawer. Therefore, the regulator is set to the average value read by the sensor, which is usually located near the wall or in the lampshade.
In winter, when the apartment is cool, the refrigerator may not turn on at all if the room temperature is lower than the one set on the regulator. In such cases (if the model is not equipped with a valve for operating at low temperatures), you have to artificially heat the thermostat zone or use a special winter kit.
Step-by-step instructions for replacing the thermostat
Replacement thermostat is one of the most accessible procedures for a home craftsman, requiring a minimal set of tools. The main safety rule is to completely disconnect the device from the power supply before starting any work. You will need a flathead and Phillips screwdriver, pliers and possibly a knife to strip the contacts.
First you need to gain access to the sensor installation location. In most models, this requires removing the plastic cover inside the refrigerator compartment, where the light bulb and control knob are located. Be careful with plastic latches, they are often fragile, especially on old refrigerators.
After dismantling the panel, you will see the thermostat itself with the wires that go to it and a capillary tube going deep into the body. Before removing, be sure to take a photo of the wire connection diagram or sketch it, since color markings from different manufacturers (Stinol, Beko, LG) may differ.
☑️ Checklist before replacement
Carefully disconnect the wires, being careful not to damage isolation. Remove the mounting strip or nut holding the regulator body in place. The most delicate part is removing the capillary tube from the channel in the refrigerator wall. Pull it very carefully, without jerking, so as not to tear it. The new sensor is installed in the reverse order; the tube must be pushed into the channel to the same depth as the old one.
⚠️ Attention: Technical characteristics of thermostats (on/off temperature, tube length) may differ even within the same brand. Always select a spare part according to the full catalog number indicated on the body of the old regulator, and not just by the model of the refrigerator.
Prevention and extension of service life
In order to temperature regulator serve for a long time, it is important to follow the operating rules refrigerator. Do not set the regulator to the maximum value unless necessary. Constantly working at the limit accelerates the wear of springs and contacts, and also leads to excessive ice formation on the evaporator, which impedes heat transfer.
Regular defrosting (for drip systems) helps maintain normal temperature conditions. If the evaporator is covered with a thick layer of ice, the temperature sensor may not read correctly because the ice acts as an insulator. Once every 6-12 months (depending on the model), completely defrost the unit.
Make sure the door is closed tightly. If the seal is worn out and warm air constantly enters the chamber, the compressor will work for wear, trying to compensate for heat loss. In such a situation, the thermostat will constantly keep the contacts closed, which will reduce the life of both the motor and the regulator itself.
Frequently asked questions (FAQ)
Why does the refrigerator click but does not turn on?
This is a classic sign of a faulty start relay or a jammed compressor, but sometimes it behaves this way and a faulty thermostat that cannot close the circuit. If the refrigerator starts when you bridge the thermostat contacts, change the regulator.
Is it possible to install a thermostat from another refrigerator model?
Technically possible if the mounting dimensions and tube length are the same. However, the on and off parameters (temperature differential) may not be suitable. This will lead to either frequent switching on or overfreezing of food. It is better to look for the original or a complete analogue.
How to understand that the electronic sensor is broken and not the board?
You need to ring the sensor with a multimeter. If it shows infinite resistance or zero at room temperature (and does not change readings when heating/cooling), the sensor is faulty. If the resistance changes smoothly, there is a problem in the control board or wiring.
Why is there a lot of ice on the back wall of the refrigerator, although the thermostat is new?
Perhaps the capillary tube of the new thermostat is not immersed deep enough in the channel or does not fit tightly to the evaporator. Also, the reason may be a freon leak or a malfunction of the defrost system (heating element or timer), and not in the regulator itself.