The situation when refrigerator emits a characteristic hum, but room temperature remains inside, is one of the most common and frightening for the owner. A hum indicates that the motor is trying to start or is idling, but the refrigerant is not circulating or is not circulating efficiently enough to remove heat from the chambers. This condition requires immediate attention, since prolonged ignoring of the problem can lead to complete failure of an expensive unit and damage to food.
The first thing you need to do is listen to the nature of the sound. If it is a steady hum followed by clicks, or a strained hum that ends abruptly, the troubleshooting algorithms will be different. In most cases, the problem lies in the electrical part of starting the engine or in a violation of the tightness of the system, which requires a qualified approach. However, primary diagnostics can be carried out independently in order to exclude trivial causes and understand whether it is worth calling a specialist.
It is important to understand that modern cooling systems, whether classic drip or advanced No Frostdepend on the well-coordinated operation of the compressor. If the engine is running but there is no cold, it means the gas compression and expansion cycle is broken. Below we will analyze in detail the mechanical, electrical and physical causes of such a breakdown, as well as methods for eliminating them.
⚠️ Attention: If you hear a strong metallic knock, crackling sound or smell a burning smell, immediately disconnect the device from the power supply. Further operation in this mode may lead to a fire or jamming of the piston group.
Problems with the starting relay and motor electrical
The most likely reason why compressor it hums, but does not start, is a malfunction of the starting relay. This small device is responsible for supplying a starting pulse to the motor winding. Over time, the contacts oxidize, and the heat-sensitive tablet inside the relay loses its properties. As a result, the motor receives voltage, hums, trying to turn over, but the starting current is not generated, and after a few seconds the thermal protection is triggered, turning off the unit.
Diagnostics can be carried out visually and using a multimeter. Remove the back cover of the refrigerator, find the black compressor cylinder and the plastic box on the side - this is the relay. Carefully remove it, shake it: if a ringing sound is heard inside, it means the core has collapsed. Also check the contacts for carbon deposits. If the relay is working properly, the problem may lie in an interturn short circuit of the windings of the motor itself, which often happens after power surges.
Replacing the start relay is a simple procedure and accessible to a home craftsman. The main thing is to choose an analogue with identical characteristics, since different types of starters are used for different models. If after replacing the relay the situation has not changed and the engine continues to hum without starting, most likely you will need to replace the compressor itself or professional rewinding, which is not economically feasible. Indesit, Atlant or Liebherr different types of starters are used. If after replacing the relay the situation has not changed, and the engine continues to hum without starting, most likely, the compressor itself will need to be replaced or professional rewinding, which is not economically feasible.
☑️ Diagnostics of the start relay
Freon leakage and violation tightness
If the engine runs smoothly, without clicks and attempts to start, but the chambers are warm, there is a high probability of refrigerant leakage. Freon circulates in a closed circuit, and its quantity is strictly regulated. When the pressure in the system decreases, the compressor begins to run idle, pumping vapor instead of gas, which does not provide the necessary cooling effect. Leaks often occur in places where tubes are soldered, in the evaporator (especially if it was wiped during defrosting) or in the foamed part of the housing.
It is rarely possible to determine a leak visually, since the gas evaporates quickly. An indirect sign may be swelling of the side walls of the refrigerator or the appearance of oily spots under the unit. Also pay attention to the condenser grille at the back: if the freon is gone, it will be cold or slightly warm only at the entrance, and not hot over the entire area, as it should be during normal operation.
Why can’t you just add freon?
Simple refueling without looking for leaks is a temporary measure. The gas will come out again through the same hole, and the compressor will burn out due to operation without proper cooling by the oil that circulates along with freon.
Repair in this case requires calling a technician with equipment to evacuate the system and refill the refrigerant. It is impossible to find a micro-crack on your own and solder it without a special tool. The technician will perform a nitrogen pressure test to find the leak, eliminate the defect, replace the filter drier and fill the system with new gas. This is a standard procedure that restores life to many refrigerators.
Malfunctions of the thermostat and temperature sensors
Another reason why refrigerator it can hum non-stop, but does not freeze well, is sticking of the thermostat contacts or a malfunction of the electronic sensor. If the thermostat is stuck in the on position, the compressor will run continuously, trying to reach an unattainable temperature. This leads to freezing of the evaporator and, as a consequence, to disruption of heat exchange.
In models with electronic control (No Frost), sensors are responsible for the temperature. If the sensor transmits incorrect data to the control module, the system may not give a command to turn off the compressor or, conversely, not start defrosting. You can check a mechanical thermostat by closing its contacts directly: if the refrigerator operates normally, then the regulator needs to be replaced.
A symptom of problems with thermoregulation is often the formation of a “fur coat” or ice block in the freezer, while the refrigerator compartment may be warm. This happens because ice blocks the cold air circulation channels. In such cases, it is necessary to completely defrost the refrigerator within 24 hours before starting diagnostics of the electronics.
Clogged capillary tube
Capillary The tube is a thin copper channel where throttling (a sharp decrease in pressure) of the refrigerant occurs. If there is moisture or oil oxidation in the system, an ice plug or particulate blockage may form. In this case, compressor hums, creating pressure, but freon cannot pass through the narrow section of the tube, and circulation stops.
A characteristic sign of a blockage is the temperature of the condenser: it can be hot at the beginning and cold after the blockage occurs. The compressor may also become hotter than usual because it has to work under increased load. Sometimes tapping the tube helps, but this is a temporary measure that does not solve the problem of moisture or debris in the system.
Removing the blockage requires professional purging of the system with high-pressure nitrogen, replacing the filter-drier and vacuuming. The filter retains moisture and dirt, and its replacement is required whenever the circuit is opened. Ignoring this step will lead to the re-formation of the ice plug in a short time.
| Symptom | Probable cause | Sound character | Condenser temperature |
|---|---|---|---|
| Clicking and humming | Faulty start relay | Humming for 3-5 seconds, then clicking | Cold |
| Works without stopping | Freon leak or blockage | Smooth hum | Partially warm or cold |
| Humming and heating | Compressor jammed | Strained hum | Warm at the outlet |
| Humming, but slightly freezing | Wear of the piston group | Quiet hum | Warm, but not hot |
Wear of the compressor piston group
With age, the resource of any mechanism is exhausted. In the compressor, the piston rings and cylinder walls wear out. As a result, compression drops: the engine is running, the shaft is rotating, but the gas is not compressed to the required pressure. Freon It is simply pumped from one side to the other without effective compression, so there is no cold, although the sound of the engine is present.
Checking compression at home is difficult, but you can use the method "on the finger." With the engine running (shortly!) check the pressure at the outlet of the discharge pipe. If the air stream is weak and does not dislodge your finger, it means the compressor has “died”. This is natural wear and tear, typical for refrigerators older than 10-12 years.
There is only one solution to the problem - replacing the compressor with a new one. There is no point in repairing old sealed units by opening the housing and changing the pistons: the balancing is disrupted, and such a unit will not last long. Modern compressors often come complete with an already installed start relay, which simplifies replacement.
Problems with the No Frost system
In refrigerators with the system No Frost the situation when the compressor hums, but there is no cold, can be caused by a breakdown of the fan or defrost system. If the fan driving cold air does not work, the evaporator freezes and the cold does not enter the chambers. At the same time, the compressor works normally, trying to cool the already frozen evaporator.
The defrost heating element or timer also often fails. Ice accumulates on the evaporator, blocks the air passages, and cooling efficiency drops to zero. This can be seen visually by disassembling the back wall of the freezer: there will be a huge lump of ice that will interfere with the operation of the fan.
⚠️ Attention: Do not try to pick out the ice with a knife or screwdriver! You can damage the aluminum evaporator, and then repair will become economically impractical due to the difficulty of soldering aluminum.
To eliminate the problem, you need to check the defrost circuit: heating element, defrost sensor and fuse. Often it is the fuse that is in series with the heating element that blows. Replacing it is inexpensive, but requires disassembling the freezer. After replacing parts, the refrigerator must be defrosted for at least 24 hours.
Can a refrigerator operate without freon?
No, heat exchange is impossible without freon. The compressor will pump air, but the temperature will not drop below room temperature. Working without refrigerant is dangerous for the motor.
Frequently asked questions and answers (FAQ)
How long should the refrigerator run after turning on for cold to appear?
Usually the first signs of cooling appear 30-40 minutes after turning on. Complete cooling of the chambers to the set temperatures takes from 2 to 12 hours, depending on the volume of loaded products and the model of the refrigerator. If after an hour of operation of the compressor the walls of the chamber remain warm, and the condenser at the back is cold, this is a sign of a malfunction.
Is it possible to operate a refrigerator if it hums, but does not freeze?
It is strictly not recommended. Operating the engine without normal load (if freon leaks) or with overheating (if clogged) leads to burnout of the windings. In addition, bacteria will begin to multiply in the chambers and the food will spoil. It is better to turn off the device and carry out diagnostics.
Why is the compressor hot to the touch?
In operating condition, the compressor heats up to 60-80 degrees Celsius, this is normal, since heat is released when the gas is compressed. However, if you cannot touch it with your hand for a couple of seconds, or you smell a burning smell, this is a sign of overheating due to a malfunction, blockage or ventilation problems (if the refrigerator is located close to the wall).
Is it worth repairing an old refrigerator or is it easier to buy a new one?
If the refrigerator is less than 7-8 years old, repairs are usually justified. Replacing the compressor or fixing the leak will pay off. If the equipment is more than 12-15 years old, the cost of spare parts and labor can be 50-70% of the price of a new budget model, and in this case, buying a new device will be a more rational decision.