The situation when you open the refrigerator, and it’s warm, although the engine is humming and gets very hot, is familiar to many owners of household appliances. This is a classic sign that the compressor is wearing out, trying to build up pressure, but the refrigeration circuit is not performing its function. Instead of cooling the chamber, the unit turns into a heat gun, consuming electricity and creating an emergency situation.
Many people mistakenly believe that if the motor hums and vibrates, it means the system is working properly, and you just need to wait. However, in this case high temperature of the compressor housing (often up to 80-90 degrees) indicates critical overheating. This occurs because the coolant is not circulating properly or there is a lack of compression, causing the engine to idle. It is strictly forbidden to leave the equipment in this mode of operation.
In this article we will analyze in detail the mechanics of the process, explain why heat transfer is disrupted, and help determine whether the problem can be solved independently or a call to a specialist is required. Understanding the nature of the malfunction will help you avoid unnecessary expenses on diagnostics and prevent complete combustion of the motor windings due to long-term operation in emergency mode.
The principle of operation and the role of compression
To understand why refrigeration unit stopped freezing when the engine is running, you need to remember the basics of thermodynamics. The compressor is the heart of the system, compressing Freon gas into a liquid under high pressure. It is this compression process that is accompanied by a sharp release of heat, so the rear grille and the engine itself are always hot. If there is a heat sink, but there is no cold, then the cycle is interrupted.
In the normal state, hot gas passes through the condenser, cools and turns into a liquid state, after which it enters the evaporator through a capillary tube. There, the pressure drops sharply, and the freon boils, taking heat from the refrigerator chambers. If refrigerant circulation is broken at any stage, the compressor continues to pump gas, but effective heat exchange does not occur. As a result, all the energy is converted into heat, which remains inside the system.
A frequent reason for the lack of cold is the loss of tightness of the circuit. Even a microscopic hole, invisible to the eye, leads to a gradual release of freon. The pressure drops, the compressor tries to compensate for the lack of gas by working continuously. At some point, its power ceases to be enough, and temperature in the chambers begins to increase, although the motor hums without stopping.
Refrigerant leak: symptoms and diagnosis
The most common reason why a refrigerator stops working freezing is a banal freon leak. Gas can escape through microcracks in the evaporator, which are formed due to corrosion, or through poor-quality soldering of connections. Visually detecting a leak is almost impossible without special equipment, but indirect signs will indicate a problem.
Pay attention to the behavior of the motor. When there is a leak, it works almost without interruption, trying to reach the set temperature. Since there is little gas in the system, it does not have time to cool in the condenser and returns to the compressor too hot. This causes overheating of the windings a protective shutdown or, in the worst case, an interturn short circuit. You may also notice swelling of the side walls of the refrigerator if the tubes are built into the body.
⚠️ Attention: If you hear a hissing or whistling sound coming from the back of the refrigerator, immediately unplug the appliance. This may indicate an active release of gas under pressure, which creates a risk of ignition in the presence of a spark.
For accurate diagnosis, technicians use leak detectors or the soap foam method. You can independently try to check the temperature of the tubes at the back by touch: if one of them is cold and the other is barely warm (instead of hot), this is a sure sign of a lack of freon. It is also worth inspecting the floor under the refrigerator for oily stains - freon often comes out along with compressor oil.
Clogged capillary tube
The second most common cause of cooling system failure is clogged capillary tube. This unit is a thin copper channel through which liquid freon enters the evaporator. Over time, oil oxidation products, moisture, or solids can accumulate in the system and clog the passage. As a result, hydraulic resistanceis created, and circulation stops.
When clogged, the compressor begins to work with increased load, trying to push the refrigerant through the plug. The pressure at the outlet of the compressor increases, the temperature of the engine housing becomes extremely high. A characteristic sign of this particular malfunction is that the condenser (grid at the back) can be hot only in the first half, and then cold. This means that the freon is stuck in a plug and does not move further along the circuit.
Sometimes the blockage is temporary and is caused by the freezing of moisture inside the tube. In such cases, the refrigerator may periodically begin to freeze after defrosting, but after a few days the problem returns. However, most often, mechanical cleaning of the system or replacement of the filter-drier is required, which is a complex procedure that requires evacuation of the circuit.
Why does blockage occur?
The main reason is moisture entering the system due to poor-quality repairs or depressurization. Water reacts with freon and oil, forming acid and solid deposits, which clog the capillary.
Failures of the compressor itself
The most unpleasant scenario is the failure of the compressor itself pumping unit. The compressor may hum and heat up, but not create the necessary pressure. This occurs when internal mechanical parts such as pistons, valves or connecting rods wear out. In this case, the motor consumes electricity, vibrates, but is physically unable to compress the gas to the desired state.
You can determine the loss of compressor performance by disconnecting it from the system and checking the blowing force. If air barely blows from the outlet pipe, and your finger does not feel a powerful flow, it means the mechanical part is worn out. Also, a sign of a malfunction may be too quiet operation or, conversely, a loud metallic knock inside the housing.
Another problem is jamming of the rotor or bearings. In this case, the starting relay tries to start the engine, a click is heard, the motor hums for several seconds, gets very hot and is turned off by the thermal relay. After some time, the cycle repeats. Operating a refrigerator with a jammed motor is dangerous, as this can lead to a wiring fire.
☑️ Compressor diagnostics
Problems with the starting relay and electrical wiring
Sometimes the compressor itself is working, but cannot start or work correctly due to faults in the electrical chains. The key element here is the start-up relay. It supplies an impulse to the starting winding to start the rotor. If the relay is stuck or burnt out, the motor may hum but not start, or may start jerkily, causing excessive heat.
It is also worth checking the capacitor (if your model has one) and wiring. Oxidized contacts, burnt terminals or damaged insulation lead to voltage drop. The motor tries to operate at low voltage, the current in the windings increases, and the device heats up, not delivering the required power. Visual inspection of the contacts often helps to identify traces of carbon deposits.
In some modern models with inverter compressors the problem may lie in the electronic control module. It regulates the frequency