The refrigerator is the heart of a modern kitchen, and its stable operation directly affects the safety of food. However, sometimes an attentive owner notices that refrigerator compressorwhich should normally be hot suddenly becomes cold. This phenomenon often causes bewilderment and even panic, because heat is thrown out rather than absorbed from the chamber.
The physics of the cooling process implies that the refrigerant, passing through the system, gives off heat to the environment precisely in the area of the motor-compressor. If you touch the back wall of the unit and feel cold, this is a signal that freon circulation it is broken or the engine itself is not performing its gas compression function. In this material we will analyze in detail the mechanics of the process and possible breakdowns.
It is worth noting right away that diagnostics must be carried out on a working device. If the unit is turned off for several hours, then its temperature is equal to room temperature, and this is normal. But if the refrigerator hums and compressor housing remains icy, then the system is not working correctly, and this cannot be ignored.
Physics of the process: how the cooling system normally works
To understand the problem, you need to briefly refresh your memory on the principle of operation of a household refrigerator. The main element here is the compressor, which works like a pump. It compresses the refrigerant gas, increasing its pressure and temperature. That is why in normal operation rear grille the motor itself heats up.
Hot gas under pressure enters the condenser (black coil at the back), where it cools and turns into a liquid state. Next, passing through the capillary tube and evaporator, freon boils at low pressure, actively taking heat from the refrigeration chamber. If this cycle is interrupted, compressor temperature can behave unpredictably.
It is important to understand that the motor itself does not produce cold. It only ensures the movement of freon. If you feel cold coming from the engine housing, this often means that it is receiving already cooled gas from the evaporator, which has not been properly compressed or is simply not circulating in a large circle.
⚠️ Warning: Never try to measure the temperature of a running compressor with wet hands or metal objects to avoid electric shock or short circuit.
Main reason: lack of refrigerant circulation
The most common reason why the compressor remains cold is that freon does not enter its working chamber for compression. This may be due to a refrigerant leak or a blockage in the system. In this case, the motor runs idle, pumping vapors, but without creating the necessary pressure.
If a freon leakhas formed in the system, then the amount of gas is critically small. The compressor tries to suck gas from the evaporator, but there is none there. As a result, warm air from the room can flow through the suction tube to the motor, but due to the lack of compression, the housing itself does not heat up, and sometimes even cools due to the expansion of remaining gas.
Another option is clogging of the capillary tube. An ice or debris plug forms in the system. The pressure at the compressor inlet drops and circulation stops. The motor hums, but no heat exchange occurs. In this case lack of heating of the compressor is a sure sign that freon does not circulate in a closed circuit.
- 🧊 Refrigerant leakage through microcracks in the circuit.
- 🛑 Blockage of the filter-drier or capillary tube.
- 💨 Air or moisture getting into the cooling system.
Faults in the starting relay and electrical part
The electrical component of the refrigerator is no less important than the mechanical one. Often the situation when the engine is cold is due to the fact that it simply does not start, although a humming noise may be present. It is responsible for starting starting relay, which supplies an impulse to the starting winding.
If the relay is faulty, it may click, trying to start the engine, but the rotor does not take off. At this moment, current flows through the windings, but no mechanical compression work occurs. The case may warm up slightly from the current, but will not heat up to operating temperature, and in some cases will remain cold due to the short duration of switching on.
It is also worth checking the integrity of the motor windings. If it occurs winding breakthen the electrical circuit is open. The engine will not hum at all, but if the break is partial or there is a short circuit, the behavior may be strange. In any case, without rotation of the pistons, there will be no gas compression, and no heating either.
A multimeter is often required for electrical diagnostics. It is necessary to “ring” the windings for resistance and check whether the relay closes the contacts when voltage is applied. This requires certain skills in working with electrical appliances.
☑️ Electrical diagnostics
Problems with the thermostat and sensors
Sometimes the problem lies not in the compressor itself, but in the control system. Thermoregulator (or an electronic sensor in modern models No Frost) gives the command to turn on the engine. If the sensor “lies” and shows that it is already cold in the chamber, the motor may not turn on at all or work with long interruptions.
In models with electronic control, failure control unit can lead to incorrect voltage supply to the starting relay. The motor may receive insufficient power to start, or turn on for a split second. In such modes, the compressor remains cold, since a full compression cycle does not occur.
It is also worth mentioning the defrost sensors in the systems No Frost. If they are faulty, the system may “think” that a defrosting process is in progress and block the compressor from starting. Visually, it looks like a cold motor when the refrigerator is plugged in.
| Symptom | Possible cause | Sound character |
|---|---|---|
| The compressor is cold, silence | The thermostat is faulty or there is no power | Absent |
| The compressor is cold, humming | Freon jammed or leaking | Monotonous hum |
| Compressor is cold, clicks | Start relay burnt out | Frequent clicks |
| Compressor is warm, but does not freeze | Partial loss of freon | Works constantly |
Rare cases: inverter compressors
Modern refrigerators are often equipped with inverter compressors. Their operating principle differs from the classic ones: they do not turn off completely, but smoothly change power. In temperature maintenance mode, such a motor can operate at very low speeds.
In this mode, the motor housing may be barely warm or even seem cold to the touch, especially if the room is cool. This is not always a sign of a breakdown. Inverter systems LG or Samsung are designed to minimize energy consumption and noise.
However, if the refrigerator has stopped freezing and the motor is barely warm, this may indicate an error in the inverter control board. The system could go into emergency mode or incorrectly read data from sensors, without giving a command to increase power.
How to distinguish an inverter compressor?
Inverter models usually operate quieter and do not have the characteristic loud clicks when turning on/off, since the motor does not stop completely. The case is often marked “Inverter.”
Methods of self-diagnosis
Before calling a technician, you can carry out an initial diagnosis. The first thing to do is listen. If the engine hums but is cold, this is one scenario. If there is silence, it is different. It is also worth checking whether the condenser grille at the back is heating up. If it is cold when the engine is running, it means that freon is not circulating.
You can carefully (following safety precautions) check the temperature of the suction tube (usually copper, thicker). If it is covered with frost right at the exit from the compressor housing, and the motor itself is cold, this is a sign that liquid freon is “flying” into the motor, which is deadly for it.
Checking the start relay requires removing it from the compressor. If you hear a ringing sound inside when you shake it (as if from broken ceramics), then the relay is faulty and needs to be replaced. This is one of the simplest and cheapest faults that you can fix with your own hands.
⚠️ Attention: Opening a sealed circuit to check the pressure or refill with freon is strictly forbidden to do on your own without special equipment and a license.
When you need to call a specialist
Independent repair is possible only in cases of replacing the thermostat, relay or checking the wiring. If the problem lies in freon leak or a clog in the system, a call to the technician is required. Only a specialist has a vacuum pump, a pressure gauge station and a supply of refrigerant.
The process of restoring the tightness involves finding the location of the leak (often these are sealed places or the evaporator), soldering copper pipes, replacing the filter-drier and evacuating the system. This is a complex technological process that cannot be reproduced at home.
Ignoring the problem when the compressor is cold can lead to combustion of the engine itself. Working “dry” or with liquid refrigerant quickly destroys the expensive unit. Therefore, if simple methods (defrosting, checking the relay) did not help, there is no need to delay repairs.
Frequently asked questions (FAQ)
Can the compressor be cold if the refrigerator has just been defrosted?
Yes, immediately after defrosting and turning on, the refrigerator can work in enhanced mode, but the compressor itself will begin to heat up after 15-20 minutes of operation. If more than an hour has passed and it is icy, there is a malfunction.
Is it dangerous to touch a cold compressor with your hand?
The cold itself is not dangerous, but if there is a breakdown of the insulation on the housing, you may get an electric shock. In addition, a sharp temperature change (if your hand is wet) can damage the paintwork or cause corrosion.
How much does it cost to replace a compressor if the old one is burned out?
The cost consists of the price of a new unit, the cost of refrigerant, filter and the work of a technician. On average, this is a significant part of the price of a new refrigerator, so it is often more advisable to buy new equipment.
Why does it hum, but does not start?
Most likely, the piston in the cylinder is jammed or the start relay has failed. The motor tries, hums from tension, but cannot crank mechanically.