The situation when the refrigerator operates continuously, without turning off for a minute, is familiar to many owners of household appliances. Normally, the compressor should turn on and off at certain intervals, maintaining a given temperature regime inside the chambers. If the motor hums for days on end, and a “glacier” forms inside or the food begins to deteriorate, this is a sure sign that the control circuit is broken.
Most often, the culprit of such an anomaly is the thermostat (thermostat), which stops sending a signal to turn off the compressor when the desired temperature is reached. However, you should not immediately run for a new part, since the problem may lie in a banal misalignment of the door or a refrigerant leak. It is important to carry out competent diagnostics so as not to replace a working part.
In this article we will analyze in detail the mechanics of the device, describe the symptoms of its breakdown and give step-by-step instructions for checking and replacing. Understanding the processes occurring inside the unit will help you save on calling a technician, or at least accurately name the cause of the breakdown when calling for service.
The principle of operation of the thermostat and its role in the cooling cycle
The thermostat is a mechanical or electronic “brain” responsible for the temperature balance. Classic refrigerator models use a mechanical sensor, which is a sealed capsule of gas or liquid connected to a bellows. This sensing tube is attached to the evaporator or placed in a special chamber inside the refrigerator compartment.
When the temperature inside the chamber rises above the standard you set, the gas in the capsule expands. This pressure is transferred to the bellows, which opens or closes the electrical contacts. As a result, compressor receives power and begins to pump refrigerant. As soon as the temperature drops to a predetermined minimum, the process proceeds in the reverse order: the gas is compressed, the contacts open, and the motor stops.
If this cycle is interrupted at the stage of opening the contacts, the refrigerator turns into a cold generator without stopping. Electronic control modules found in modern models LG, Samsung, Boschwork on a similar principle, but instead of gas they use thermistors that change their resistance depending on the heat.
⚠️ Attention: In older models with mechanical control, adjustment is carried out by turning the knob. If the handle scrolls endlessly or, conversely, is stuck in the “Maximum” position, the mechanism could simply physically collapse inside.
Failure in the operation of this unit leads not only to excessive energy consumption, but also to accelerated wear of the compressor. An engine that runs without rest breaks overheats and its service life is reduced significantly. Therefore, the continuous operation of the unit cannot be ignored.
Main symptoms of a malfunctioning thermostat
You can determine that the problem lies in the thermostat by a number of characteristic signs. The first and most obvious symptom is the absence of periods of rest. The refrigerator can hum for hours, even if you just opened it and put food in it, which usually causes it to turn on briefly.
The second sign is excessive freezing. If a thick “coat” of ice forms on the back wall of the refrigerator compartment, and food near the wall freezes or spoils from the cold, it means that the temperature has dropped below the permissible minimum, but no shutdown has occurred. In the freezer, overcooking of food may occur due to too low a temperature.
The third symptom is related to the behavior during defrosting. If you defrost the refrigerator completely, leave it with the doors open for several hours, and then plug it in, a working unit should gain temperature and turn off. If it has been running for several hours, it’s cold inside, the compressor is hot, and there’s still no shutdown click - this is a direct indication of a sensor malfunction sensor malfunction.
- ❄️ An ice crust forms on the back wall of the refrigerator compartment even at normal humidity levels.
- 🔊 The compressor operates without interruption for more than 12-24 hours, producing a characteristic hum.
- 🥩 Food in the refrigerator compartment freezes or, conversely, quickly deteriorates due to a violation of the cycle.
- 🌡️ When you turn the thermostat knob, you do not hear a characteristic click (in mechanical models).
It is worth noting that in some cases the refrigerator may not turn off due to a loose door fit, but then the ice will build up unevenly, and the compressor will turn on more often than usual, but still turn off. The thermostat “removes” the shutdown phase completely.
Other reasons for the continuous operation of the refrigerator
Before dismantling the thermostat, it is necessary to exclude other factors that simulate its breakdown. Often users start to blame the sensor when the problem lies in a violation of heat exchange or the tightness of the circuit. For example, if the rubber seal on the door is worn out, warm air constantly enters the chamber.
The refrigerator “sees” that the temperature has not dropped to normal and continues to work. The thermostat in this case is working, it is simply doing its job honestly - trying to cool the incoming heat. A similar situation occurs when the capillary tube is clogged or there is a freon leak: there is not enough cold, so the automation does not give the command to stop.
It is also worth checking the location of the equipment. If the refrigerator is standing close to the wall or in a niche without gaps for ventilation, the radiator on the back wall does not have time to cool down. The compressor overheats, cooling efficiency drops and the cycle does not complete. In modern models with the system No Frost the cause may be a malfunction of the fan or defrost heating element.
| Symptom | Thermostat is faulty | Freon leakage / Clogging | Problem with door |
|---|---|---|---|
| Operating mode | Works non-stop | Works non-stop or in short cycles | Turns on very often |
| Inside temperature | Strong cold, ice | Warm or not cold enough | Increased, especially at the door |
| Frost on the evaporator | Uniform, thick layer | Partial or only at the entrance tubes | Uneven |
| Compressor temperature | Very hot | Barely warm or hot | Normal or hot |
Diagnostics must be comprehensive. If during continuous operation there is heat inside the refrigerator, it is definitely not the thermostat, but a loss of refrigerant. If there is an “Arctic” inside and the motor does not stop, the probability of the temperature controller breaking down is close to 90%.
Diagnostics of the thermostat: checking with a multimeter
To accurately confirm the diagnosis, you will need a minimum set of tools: a screwdriver and a multimeter (tester). Before starting any work be sure to unplug the refrigerator. Safety is the number one priority when repairing household appliances.
First you need to get to the thermostat. In most models, it is located inside the refrigerator compartment, under a plastic cover, or outside, above the door. Remove the regulator knob and protective cover. You will see a device with wires approaching it and a capillary tube going deep into the body.
Disconnect the wires from the thermostat contacts. Set the multimeter to continuity or resistance measurement mode. Connect the tester probes to the contacts of the removed thermostat. At room temperature, a working mechanical thermostat should “ring” (show zero or close to zero resistance), since its contacts are closed.
⚠️ Attention: If you have an electronic thermostat (with a display on the outside), ringing the contacts may not produce results. Such sensors are checked by changes in resistance during cooling or replacement with a known good one.
For a final check of the mechanical device, you can conduct a cooling experiment. Immerse the sensing tube (if removable) or the entire unit (carefully without soaking the contacts) in cold water with ice for 2-3 minutes. After this, check the contacts again: they should open and the tester will stop beeping. If the contacts remain closed even in the cold, the part is faulty and requires replacement.
Step-by-step replacement of the thermostat with your own hands
If the diagnostics confirmed a breakdown, the thermostat must be replaced. It is important to purchase a similar model, as they differ in the length of the capillary tube, temperature range and mounting method. The part number is usually indicated on the body of the old regulator.
The replacement process begins with dismantling the old part. Carefully move the capillary tube away from the evaporator, making a note or photograph of how it was secured. Often it is inserted into a special hole or pressed with a bar. Do not damage the thin tube - there is gas inside, and its tightness is critical.
Install the new thermostat in the reverse order. Secure the case, connect the wires according to the diagram (or simply in the same order as they were, if you did not mix them up). Pay special attention to the placement of the sensitive tube: it should be in close contact with the surface that it should “feel.”
☑️ Checklist before turning on
After assembly, do not rush to load the products. Turn on the empty refrigerator and let it run for 2-3 hours. It should gain temperature and turn off on its own. If the cycle was successful, the repair can be considered complete.
Features of electronic thermostats and control modules
In modern refrigerators with a system Full No Frost and digital control, mechanical thermostats are rarely found. Here, the temperature control function is performed by sensors (thermistors), which transmit data to the electronic control module. If such a refrigerator does not turn off, the reason may not be in the sensor itself, but in the “brains” or wiring.
Electronic sensors are checked by measuring their resistance. Each manufacturer (Indesit, Atlant, Beko) has a table corresponding to resistance and temperature. For example, at 20°C the sensor may show 5 kOhm, and at 0°C - 12 kOhm. If the device shows a break or resistance that does not change during cooling, the sensor is faulty.
Often in such models, an error code lights up on the display, indicating a problem with the temperature sensor. However, sometimes the control module gets stuck and does not send a command to turn off the compressor, even if the sensor is working. In this case, professional diagnostics of the board is required.
Is it possible to temporarily bypass the thermostat?
Technically, you can short the wires directly so that the refrigerator works constantly. But this is an emergency measure: without temperature control, the food in the back will freeze, and the compressor will burn out in a few days. Use only for short-term preservation of products until the technician arrives.
Repairing electronic parts with your own hands is only possible if you have the skills to work with a soldering iron and circuits. Most often, owners limit themselves to replacing the sensor itself, which is inexpensive and easy to change.
Prevention and operating recommendations
In order for the thermostat and the entire cooling system to serve for a long time, it is important to follow the operating rules. Do not put hot food in the refrigerator - this creates a false load on the sensor and causes the compressor to work harder. Sudden temperature changes are harmful to any components.
Check the door seal regularly. A simple test with a piece of paper clamped around the perimeter of the door will help identify weak points in the seal. If the paper falls out easily, the rubber band needs to be washed, heated with a hairdryer, or replaced.
Also keep the condenser on the back wall clean. Dust and animal hair act as a heat insulator, interfering with heat transfer. This makes the system think that cooling is slow and prolongs the operating time of the compressor.
Following these simple rules will extend the life of your refrigerator and avoid situations where it works for days on end. Remember that prevention is always cheaper and easier than urgent repairs or buying new equipment.
Frequently asked questions (FAQ)
Can a thermostat stick and how to “reanimate” it?
In mechanical models, the contacts inside can oxidize or “stick” due to sparking. Sometimes quickly turning the control knob from minimum to maximum and back again helps. This can break up the oxides. However, this is a temporary measure: if the mechanism is worn out, after a week the problem will return and a replacement will be required.
Why does the refrigerator still not turn off after replacing the thermostat?
There may be several reasons: the capillary tube is installed incorrectly (does not fit tightly enough to the evaporator), the wrong type of thermostat is selected (with a different temperature range), or the problem is not thermostat, but in a freon leak or a clogged system. It is also worth checking whether the wires are mixed up when connecting.
How long does a thermostat last on average?
The average service life of a mechanical thermostat is 5-7 years of intensive use. Electronic sensors can last longer, but they are more sensitive to power surges. Frequent voltage surges are the main enemy of refrigerator electronics.
Is it dangerous to leave the refrigerator running without stopping overnight?
For a short time (one night) - not dangerous, although undesirable. Long-term operation without shutting down leads to overheating of the compressor windings and eventual combustion of the motor. If you notice such a problem, it is better to temporarily reduce the load (reduce power) and call a technician.