In every modern refrigerator, be it an old Soviet model or the latest smart unit, there is an invisible but critical element. This is a thermostat, which is often called the “heart” of the refrigeration system, although technically it functions as the brain that makes decisions about turning the compressor on and off.
It is this small device that ensures a stable temperature inside the chambers, allowing food to remain fresh for weeks. Without it, the refrigerator would turn into a freezer that freezes all the contents, or, conversely, into a warm chamber where food will quickly spoil.
Understanding this what does a thermostat do for a refrigeratorwill help you quickly diagnose a breakdown and, possibly, save on expensive repairs. In this article we will analyze the design of the device, the symptoms of its failure and nuances that are rarely mentioned in the instructions.
The principle of operation of the thermostat
The main task of the thermostat is to control the temperature inside the refrigerator compartment. It continuously reads the data using a sensing element and transmits a signal to the compressor. When the temperature rises above a predetermined threshold, the circuit closes and the motor starts working.
As soon as the air inside the chamber is cooled to the desired value, The thermostat opens the contacts. The compressor stops and a rest period begins. This cycle is repeated constantly, ensuring a stable microclimate.
It is important to understand that there are different types of sensors. Older models use mechanical devices that work on the principle of expansion and compression of gas or liquid in a capillary tube. In modern units, this role is taken on by electronic sensors that transmit data to the control board.
- 🌡️ Mechanical thermostats respond to a physical change in pressure in the bellows, which leads to a click of the contacts.
- 💻 Electronic sensors use thermistors, the resistance of which varies depending on the temperature of the environment.
- ⚙️ Hybrid systems can combine mechanical control of the dampers with electronic control of the compressor.
Regardless of the type, thermostat always strives to keep the temperature within user-specified limits. If you turn the knob to the maximum, you simply change the response threshold, causing the compressor to work longer.
Where is the temperature sensor
The location of the thermostat depends on the design of the refrigerator and the type of cooling system. In classic models with one chamber and a drip defrosting system, the sensor is often located inside the refrigerator compartment.
Usually this is a plastic case with an adjustment knob, from which a long metal tube extends - a capillary. The end of this tube is attached to the evaporator or a special plate to accurately read the cooling temperature.
⚠️ Attention! In models with a system No Frost the thermostat is often hidden behind plastic panels inside the chamber or even taken outside into the technical compartment, since there is no ice there that interferes with heat transfer.In two-chamber refrigerators the situation is more complicated. There may be a separate sensor for the freezer and the refrigerator. Sometimes the sensor in the freezer takes over the main control, and in the upper compartment the temperature is regulated by a damper.
If you are planning a replacement, you need to know exactly the model of your unit. The location of elements among brands Indesit, Atlant or Bosch can differ radically even within the same year of manufacture.
Symptoms of a thermostat malfunction
You can determine that the thermostat has failed by a number of characteristic signs. Most often, owners notice that the food in the refrigerator has begun to deteriorate or, conversely, freeze.
If the compressor runs continuously without turning off for hours, and the temperature inside drops below normal, this is a sure sign of contacts sticking in the “on” position. In this case, the thermostat does not give a command to stop. the motor.
The opposite situation, when the refrigerator is silent and does not turn on, also indicates a problem. The contacts could oxidize or burn out, breaking the electrical circuit. The compressor simply does not receive voltage to start.
- ❄️ The food in the refrigerator compartment freezes, although the regulator knob is set to minimum.
- 🔥 It is warm in the chamber, the compressor does not start, although the light is on and there is current in the socket.
- 🔊 Clicks are heard, but the refrigerator does not start or operates in too short cycles.
Sometimes the problem lies not in the device itself, but in a leak in the capillary tube. If the filler gas leaves it, the bellows will stop responding to temperature changes and the contacts will remain open.
Diagnostics and testing with a multimeter
Before buying a new part, you need to make sure it is faulty. The most reliable way is to ring the contacts using a multimeter. To do this, the refrigerator must be completely de-energized and the thermostat removed.
Remove the adjustment knob and unscrew the fastening screws. Carefully remove the device, being careful not to damage the capillary tube. On the case you will see the terminals to which the wires go. They need to be disconnected and the integrity of the circuit checked.
Contact state Multimeter readings Action Normal (cold) 0 Ohm (circuit closed) The device is working Open circuit Infinity (1) Replacing the thermostat Short circuit 0 Ohm at heating Sticking contacts ☑️ Checking the thermostat
Completed: 0 / 4When checking a mechanical sensor, you can place its sensitive part in a container with cold water (about +5°C). In good condition, the contacts should close. If you heat the tube in your hands, they should separate.
For electronic sensors, checking with a multimeter shows a change in resistance. The values must correspond to the specifications table for the specific model. Any sharp deviation indicates the need for replacement.
Replacing the thermostat with your own hands
If diagnostics confirm a breakdown, the thermostat can be replaced yourself if you have basic skills in working with tools. The main thing is to purchase exactly the same model or its complete analogue.
Start by disconnecting the refrigerator from the power supply. Remove the plastic cover that hides the regulator. Disconnect the wires, having previously photographed the connection diagram so as not to confuse them during assembly.
⚠️ Attention! When installing a new thermostat, make sure that the capillary tube does not touch sharp metal edges and is not pinched. This can lead to depressurization and repeated failure in a short time.Carefully insert the sensitive element into the seat. In some models, the end of the tube must be inserted into a special socket on the evaporator and fixed. Make sure it fits tightly to the surface for accurate reading.
After installation, reassemble the structure in reverse order. Turn on the refrigerator and let it run for 2-3 hours. Check whether it gets cold and whether the compressor turns off when the set temperature is reached.
Common mistakes when replacing
Independent repairs often lead to new problems if you do not take into account the nuances. One of the main mistakes is using the wrong analogue. Thermostats differ in the length of the capillary tube, temperature range and mounting method.
Incorrect installation of the sensing element is the second most common mistake. If the tube does not fit tightly to the evaporator or hangs in the air, the refrigerator will not work correctly, taking long breaks or not turning off at all.
They also often forget to check the condition of the wiring. Oxidized contacts or frayed wires can cause the new thermostat to not work. Always clean contacts and securely insulate connections. thermostat won't work. Always clean contacts and securely insulate connections.
- 🚫 Using a thermostat with a different temperature range will lead to spoilage of food.
- 🚫 Bending the capillary tube at an acute angle disrupts its operation.
- 🚫 Ignoring grounding can lead to an electric shock when touching the body.
If after replacement the refrigerator continues to behave strangely, perhaps the problem lies deeper - a freon leak or a faulty start relay. In such cases, it is better to contact a professional technician.
Questions and answers
Is it possible to temporarily do without a thermostat?
Theoretically, you can close the contacts so that the refrigerator works constantly, but this is highly not recommended. The compressor will quickly overheat and burn out, and the food in the chamber will freeze. This solution is only suitable for short-term defrosting or diagnostics.
Why does the thermostat click, but the refrigerator does not turn on?
The click means that the thermostat is working and gives a signal to start. The problem is most likely in the compressor start relay or in the motor itself. It is also worth checking for voltage in the outlet.
How often should you change the thermostat?
This element does not have a strict expiration date. With careful use, it lasts 10-15 years or more. Replacement is required only when symptoms of a malfunction appear: temperature incontinence or startup failure.
Does the temperature in the room affect the operation of the thermostat?
Yes, it does. Mechanical thermostats are sensitive to external temperature. If the room is very cold (below +10°C), the refrigerator may not turn on, since the sensor “thinks” that it is already cold enough inside.