The situation when household appliances begin to behave unpredictably always causes concern for the owner. If your the refrigerator sometimes freezes, sometimes it doesn’t, this indicates instability in the operation of the compressor unit or control system. In some cases, food may freeze into an icy crust, and after a few hours the chamber becomes warmer than necessary to preserve the food.
Such temperature fluctuations are dangerous not only for the contents of the shelves, but also for the device itself. Cyclic overloads compressor and constant attempts by the system to compensate for the loss of cold can lead to rapid failure of expensive components. Understanding the nature of these interruptions is the first step to successful repair.
In this article we will take a detailed look at the mechanical, electrical and software causes of unstable operation. You will learn how to distinguish a banal clogged drain from a serious refrigerant leak, and what steps you can take on your own, without immediately resorting to calling a technician.
Failures in the operation of the thermostat and temperature sensors
The most common reason that the refrigerator operates jerkily is incorrect operation thermostat or electronic sensors. In older mechanically controlled models, a capillary tube is responsible for temperature regulation, which can become dislodged or lose its seal. If the tube has moved away from the evaporator, it reads the temperature of the air, not the surface, which leads to delayed reactions of the system.
In modern models with a system No Frost and electronic control (for example, LG, Samsung, Bosch), thermistors perform the control function. These sensors may become inaccurate over time. The electronics receive incorrect data that the chamber is warm and turns on the compressor at full power, after which, having received a “false” signal that the norm has been reached, it abruptly turns off the cooling.
⚠️ Attention: When trying to replace the temperature sensor, be sure to disconnect the refrigerator from the power supply for at least 15-20 minutes. This is necessary to completely reset errors in the control controller.
Diagnostics of sensors requires the use of a multimeter to measure resistance at different temperatures. If the resistance values deviate significantly from the manufacturer's tabular data, the element must be replaced. Often the problem lies not in the sensor itself, but in the oxidized contacts of its connector.
How to check a mechanical thermostat?
To check a mechanical thermostat, you need to remove it and immerse the sensitive part in water with ice. If there is no click when cooling, or the contacts do not open/close when the tester rings, the part is faulty.
Problems with the starting relay and compressor
The heart of the refrigeration unit is compressor, and its stable operation directly depends on the starting relay. If the refrigerator hums but does not start, or starts for a few seconds and immediately clicks and goes silent, the problem is in the trigger mechanism. Inside the relay there is a posistor, which breaks down over time and stops supplying current to the starting winding of the engine.
Unstable operation can also manifest itself in overheating of the motor. If compressor works for too long without stopping, and then rests for a long time, the temperature inside the chamber will “float”. This often happens when the motor reaches the end of its life or at low voltage in the household electrical network, when the starting torque is not enough for stable rotation of the shaft.
It is also worth paying attention to the condition of the capacitor, if it is provided for in the design of the electric motor. Swelling or loss of capacity of this element leads to the fact that the motor cannot gain the required speed, working in the “on and off” mode.
Malfunctions of the defrost system (Defrost)
Owners of equipment with the system No Frost are characterized by the problem of the evaporator becoming clogged with ice. If the defrost timer, heating element (heating element) or defrost sensor fails, the ice coat will not melt. As a result, the fan stops driving cold air through the chamber, and the refrigerator stops freezing, although the compressor continues to work.
After some time, when the ice partially melts naturally or the emergency overheating sensor still works, the system may temporarily recover. This creates the illusion that the refrigerator “is either freezing or not.” In fact, the cooling cycle is simply blocked by an ice plug in the air ducts.
⚠️ Attention: Do not try to break off the ice with a knife or sharp objects. Damage to the evaporator tubes will lead to an immediate release of freon and will require expensive professional repairs with soldering.
For diagnostics, it is necessary to check the integrity of the defrost heating element and the resistance of the sensor. The fuse in the heater circuit often blows. If the fuse is blown, simply replacing it will not help - you need to find the reason why the heater did not turn off in time.
☑️ Diagnostics of the No Frost system
Refrigerant leak and capillary system blockage
One of the most difficult causes to diagnose is partial leak freon or formation of an ice plug in the capillary tube. Unlike a complete leak, when the refrigerator simply stops cooling, with a partial leak or a “floating” clog, operation may be unstable. The pressure in the system drops, the compressor works hard, trying to gain temperature, but cannot cope.
Clogging is often caused by moisture getting into the system or oil breakdown products. An ice plug may periodically form in a bottleneck in the capillary, blocking circulation, and then thaw when the compressor rests. This creates a characteristic effect “it works, then it doesn’t.”
| Symptom | Probable cause | Characteristic symptom |
|---|---|---|
| The refrigerator is humming, but there is no cold | Leakage freon | The compressor is hot, the condenser is barely warm |
| Periodic on/off | Clogged capillary | Gurgling sounds in the tubes, uneven heating |
| Severe freezing of the rear wall | Sensor malfunction | The ice melts only after complete defrosting |
| The compressor turns on for 1 minute | Problem with the starting relay | Loud click and silence |
Repair of the refrigerant circulation system requires special equipment: a vacuum pump, a pressure gauge station and scales for refilling. It is impossible to fix a leak or break through an ice plug without tools.
The influence of seals and the tightness of the chambers
It would seem that a simple rubber band - seal doors can cause serious temperature jumps. If the seal is worn out, dirty, or simply does not fit tightly due to the door being skewed, warm air constantly enters the chamber. Sensors detect an increase in temperature and give a command for enhanced cooling.
When the door is rarely opened, the refrigerator can cope with the load. But during active use or in hot weather, the system does not have time to compensate for the heat gain, and it becomes warm inside. After a long period of inactivity (at night), the temperature may level out, creating a false impression of serviceability.
It is also worth checking the door hinges. If they become loose, the door warps and the tight seal is broken. Sometimes it is enough to simply rehang the door or tighten the fastening bolts to restore normal operation.
Software failures and control module
In modern “smart” refrigerators, electronic control moduleis responsible for all processes. Software failures, power surges in the network or moisture ingress can lead to incorrect operation of the controller logic. The device can randomly turn the compressor on and off, ignoring sensor readings.
A full reset (Hard Reset) often helps. To do this, you need to disconnect the device from the network for a long time (from 30 minutes to several hours) so that the capacitors on the control board are discharged. This allows you to reset errors and return to factory settings.
⚠️ Attention: If the problem persists after resetting the settings and checking the electrical system, there is a high probability of failure of the control module itself. Repairing the board requires the qualifications of a radio engineer.
Some models have a self-diagnosis function that displays an error code on the display. Deciphering this code (for example, F1, E2) can accurately indicate the faulty unit, which will greatly simplify the search for the problem.
What is adaptive defrosting?
In modern models, the defrosting algorithm is adjusted to the frequency of door openings. If the system is malfunctioning, it may start defrosting too often, preventing the refrigerator from getting cold.
Frequently asked questions (FAQ)
Why does the refrigerator freeze only when the door is open?
This is a classic sign of a faulty temperature sensor or door close sensor. When you open the door, you change the position of the sensor or let in warm air, which forces the compressor to start. When closed, the system “thinks” that the norm has been reached and does not turn on.
Is it possible to use a refrigerator if it either freezes or not?
It is highly not recommended. Products in such conditions quickly deteriorate due to temperature violations. In addition, the compressor operates in extreme mode, which can lead to its complete combustion at any moment.
How often do you need to defrost the refrigerator to avoid failures?
Models with Drop System (crying evaporator) require defrosting at least once every 6 months. The systems No Frost theoretically do not require defrosting, but a preventive shutdown for a day once a year is useful to remove dust and check drainage.
Why did the refrigerator start working normally after defrosting, but a week later again?
Defrosting eliminated the ice blockage or excess ice that interfered with operation. However, the cause of ice formation (faulty heating element, sensor or freon leak) has not gone away, and the problem will return after a certain operating cycle.