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The situation when a household unit hums continuously, and the food inside begins to deteriorate, causing panic in any home cook. This is a sure sign that the cooling system has failed and the equipment has gone into emergency mode. Instead of reaching the desired temperature and stopping, the compressor continues to work to the point of wear and tear, trying to compensate for the loss of cold.
There can be many reasons for this behavior: from a banal loss of tightness to failure of the control electronics. Continuous operation of the motor non-stop is a critical signal that cannot be ignored. If you leave the problem unattended, the expensive compressor will burn out, and repairs will become economically unfeasible.
In this article we will analyze in detail the main technical malfunctions that lead to such a scenario. You will learn how to carry out initial diagnostics yourself and in which cases calling a technician becomes inevitable.
⚠️ Attention: If you smell burning or see sparking in the compressor area, immediately unplug the plug from the socket. Further operation is dangerous due to fire.
Violation of the tightness of the circuit and leakage of refrigerant
The most common reason why the refrigerator does not turn off and stops freezing is a banal freon leak. The refrigerant circulates in a closed loop, but over time, the metal of the evaporator or condenser tubes can become thin. A microscopic crack leads to a gradual release of gas to the outside.
When the amount of freon drops below a critical level, the pressure in the system decreases. Sensors detect the absence of the required temperature in the chambers and give the command to the compressor to work continuously. However, due to the lack of working fluid, cooling does not occur. The equipment hums 24 hours a day, but it is warm inside.
Often a leak occurs in the foamed part of the housing, where the hidden evaporator tubes are located. This may happen due to metal corrosion or mechanical damage during transportation. In older models, the cause is drying out of the rubber seals at the joints of the tubes.
It is difficult to diagnose a leak visually, but you can pay attention to the swelling of the back wall inside the refrigerator compartment or the appearance of oily spots under the unit. An oil stain under the refrigerator is a sure sign of depressurization of the system, since freon circulates along with compressor oil.
- 🧊 The compressor works without interruption, trying to compensate for the lack of pressure.
- 🌡️ The temperature in the chambers is higher than the established norm or equal to room temperature.
- 🔊 The sound of the engine may become strained or quieter than usual.
- 💧 The appearance of condensation or puddles of water around the unit.
⚠️ Attention: Independent refueling of the refrigerator is impossible without special equipment and a vacuum pump. A search for a leak and soldering is required.
Faults of the compressor and start relay
The heart of the refrigeration system - this is a compressor. If it is faulty, normal refrigerant circulation is disrupted. Often the problem lies not in the motor itself, but in the starting relay, which supplies voltage to the windings. If the relay is stuck or burnt out, the compressor will either not start at all, or will hum but not create pressure.
In the case of an interturn short circuit in the motor windings, the unit may operate, but its power is not enough to create the required pressure. It consumes increased current and gets very hot. Thermal protection relay in such cases, it can turn off the motor, but after cooling, turn it on again, creating a cycle of endless startup attempts.
It is also worth considering the option of loss of compression. The piston group could wear out and the valves could no longer hold pressure. In this case, freon is simply pumped from one tube to another without a cooling effect. You can determine this by touching the condenser grill on the back: it should be hot, but if the compressor breaks down, it will remain cold.
Problems with the thermostat and temperature sensors
The thermostat (thermostat) or an electronic temperature sensor is responsible for stopping the compressor. If this element fails, it sends a false signal to the control board that the chamber is too warm. Receiving such data, the electronics does not give a command to turn off the motor.
In mechanical models, the thermostat is a capillary tube with gas inside. Over time, the gas may evaporate or the tube may become dislodged, no longer making contact with the evaporator. In electronics, contacts often oxidize or the thermocouple itself fails. Incorrect sensor readings is a common cause of “endless” operation.
You can check the thermostat by temporarily closing its contacts (for mechanics) or by comparing the readings with a real thermometer inside the chamber. If the compressor starts when the contacts are closed, but does not stall when opened, the problem is in the adjusting screw or the sensor itself.
In models with the No Frost system, the sensors may become overgrown with ice if the defrosting mode is disrupted. The ice coat isolates the sensor from the air, and it shows the wrong temperature. This leads to the fact that the motor does not receive a signal about the success of cooling.
| Type of malfunction | Symptom | Probability of failure |
|---|---|---|
| Freon leak | Humming, not cooling, condenser cold | High |
| Thermostat is faulty | Does not turn off, there may be cold inside | Medium |
| Capillary clogged | Humming, condenser is partially hot | Low |
| Compressor wear | Humming, does not create pressure, gets hot | Medium |
How to check the thermostat with a multimeter?
To check the mechanical thermostat, remove it, lower the capillary tube into cold water with ice. Ring the contacts: when they cool, they should open (or close, depending on the type), making a click. If there is no reaction, the part needs to be replaced.
Clogged capillary tube
The capillary tube is a narrow channel where freon sharply expands and cools. The diameter of this channel is a fraction of a millimeter, so it becomes clogged with oil oxidation products or moisture that has entered the system. The blockage can be complete or partial.
If the blockage is partial, the refrigerator will work longer than usual, trying to break through the blockage. When completely clogged, circulation stops. The compressor pumps freon into the condenser, creating excess pressure before the blockage occurs, but the refrigerant does not enter the evaporator. The result is lack of cold and continuous operation of the motor.
A characteristic sign of a blockage is the temperature difference in the condenser: part of the grille at the back will be very hot, and part will be cold. This is the border where the freon hits the traffic jam. The filter drier may also be swollen.
Fixing this problem requires professional purging of the system with high pressure nitrogen and replacing the filter drier. It is impossible to simply clean the tube with a brush because of its length and tangles.
⚠️ Attention: Attempts to break through the blockage by increasing the voltage or knocking on the tubes can lead to rupture of the circuit and complete failure of the system.
Faults in the defrost system (for No Frost)
In refrigerators with a No Frost system, the evaporator is hidden behind a plastic panel. There is also a fan and defrost heating element located there. If the defrosting system breaks down (the heating element, timer or defrost sensor burns out), a giant coat of ice grows on the evaporator.
Ice blocks the operation of the fan and blocks the cold air supply channels into the chamber. The compressor turns on and works, but cold air simply cannot enter the refrigerator compartment. Sensors see heat and make the motor work without stopping.
To test this version, you need to defrost the refrigerator completely (at least 24 hours with the doors open). If, after defrosting, the unit started working normally and is cooling, but a week later the problem recurs, it means that one of the elements of the defrosting system is faulty.
☑️ Diagnostics of the No Frost system
The influence of external factors and operating errors
Not The reason always lies in the breakdown of parts. Sometimes the equipment is in good working order, but operating conditions do not allow it to return to normal operation. For example, if the refrigerator is located close to the wall or in a niche without gaps for ventilation, heat exchange is disrupted.
The compressor overheats, condensation efficiency drops, and the unit cannot reach the temperature. The ambient temperature also affects: if the room is +30°C or higher, a standard refrigerator will work at its maximum capacity, practically not turning off.
Densely filling the chambers with warm foods or frequently opening the door also disrupts the operation cycle. The moisture contained in the air settles on the evaporator, turning into ice, which reduces the efficiency of heat transfer.
Check the rubber seals on the doors. If they do not fit tightly, warm air constantly enters the chamber. This forces the motor to work non-stop. Check with a sheet of paper will help identify leaks: clamp the sheet with the door and try to pull it out. If it comes out easily, the rubber band needs to be changed or adjusted.
Frequently asked questions (FAQ)
Is it possible to leave a refrigerator running for several days?
If the refrigerator is working, it will turn on and off on its own. But if it no longer turns off due to a breakdown, leaving it on for a long time is dangerous. The compressor will burn out after a few days or even hours of continuous operation, since it is not designed for 24/7 operation without stopping.
Why does the refrigerator hum, but does not cool after defrosting?
Most likely, a freon leak has occurred or a blockage has formed. During defrosting, you could damage the evaporator tubes (if you cleaned them with a knife) or simply wash off traces of oil indicating a microcrack. The compressor starter could also have failed.
How long should a refrigerator operate normally?
In normal mode, the operating time ratio is about 30-40%. That is, for 10-15 minutes of work there should be 20-25 minutes of downtime. If the refrigerator runs for 40 minutes and costs 5, this is an alarming signal.
What to do if the compressor is hot but there is no cold?
A hot compressor in the absence of cold often indicates a freon leak or a clogged capillary system. In rare cases - due to loss of compression of the motor itself. You need to call a technician to measure the pressure in the system.
Is it possible to replace the thermostat yourself?
Replacing a mechanical thermostat is quite within the capabilities of a home handyman. The main thing is to buy a similar model with the same parameters and on/off temperature. Electronic sensors require more accurate diagnostics and sometimes re-flashing the board.