When a modern refrigerator stops freezing or makes uncharacteristic sounds, experienced technicians first look at the heart of the system - the compressor. It is this unit that is responsible for circulating the refrigerant, creating the necessary pressure for effective cooling of the chambers. Understanding what is inside a refrigerator compressor helps not only diagnose a malfunction, but also understand why repairs in some cases are not economically feasible.
Inside the sealed metal casing is a complex mechanism that operates under extreme conditions of high temperatures and pressure. Design designed to last for decades without human intervention, but the service life of the parts is not infinite. Knowledge of the internal structure allows you to distinguish a simple starting relay from a serious breakdown of the unit itself.
In this article we will look under the metal cover to examine in detail each element of the mechanism. You will learn exactly how the piston group compresses freon, why springs are needed, and what role oil plays in the system. This knowledge will save you from thoughtless purchases of spare parts and will help you more accurately formulate the problem when calling a specialist.
The sealed housing and its purpose
Externally compressor it is a massive black cylinder welded to the tubes. This casing is not just protection from dust, but a necessary part of the design that ensures the tightness of the system. A vacuum is created inside, and any microscopic leaks of freon or moisture penetration from the outside will instantly damage the refrigerator. That is why the body is made of two welded halves of steel, and opening it at home without special equipment and skills is a risky task.
The metal cup also serves as a reservoir for compressor oilwhich circulates along with the refrigerant, lubricating the rubbing parts. The oil level is strictly regulated by the manufacturer: if there is little of it, the mechanism will jam, if there is too much, the cooling efficiency will decrease. In the lower part of the housing you can often see vibration damping springs on which the engine itself is suspended. Such a suspension is necessary to reduce noise and vibration transmitted to the refrigerator body during operation.
⚠️ Attention: It is strictly forbidden to open the sealed compressor casing for the sake of curiosity. There may be residual pressure inside, and oil and refrigerant vapors, when in contact with an open flame (soldering iron when cutting), form toxic compounds.
In addition, electrical contacts insulated with ceramics or special sealants pass through the walls of the housing. Violation of the integrity of these inputs leads to a short circuit or current leakage to the housing, which is life-threatening. Therefore, if you see that the casing is deformed or has traces of corrosion, it is better to think about replacing the entire assembly rather than trying to weld it.
Electric motor: the heart of the system
The basis of the internal structure is electric motor asynchronous type. It is located in the lower part of the casing and is rigidly connected to the shaft of the compressor part. The engine consists of a stator, which is fixedly mounted on the housing, and a rotor rotating inside it. The stator windings are made of copper wire with high heat resistance, since during operation the temperature inside the casing can reach 110-120 degrees Celsius.
To start the engine and maintain rotation, a starting and operating winding is used. They are connected via an external start relay, which only sends an impulse at the moment of start. If you hear a hum, but the refrigerator does not start, often the problem lies in the interturn short circuit of the windings or sticking relay contacts. You can check the integrity of the windings with a multimeter by ringing the leads on the housing.
The engine rotor is mounted directly on the compressor crankshaft. Modern models use a “oscillating” rotor circuit or inverter technology, where the rotation speed is controlled electronically. However, in classic models, which are most often of interest to repairmen, the principle remains mechanical: rotational movement is converted into translational movement of the piston.
Crank mechanism
The compressor part is located directly above the engine. Here the rotational movement of the shaft is converted into a reciprocating movement of the piston. The main element here is crankshaft, which has an eccentric. This eccentric is fitted with a connecting rod, which pushes the piston up and down inside the cylinder. This entire system is immersed in oil, which is sprayed due to the rotation of the shaft, providing lubrication of bearings and rubbing surfaces.
It is important to note that in household refrigerators a piston mechanism is most often used, although there are also rotary models. In the piston version, wear of the piston group is the most common cause of loss of performance. Microscopic scuffs on the cylinder bore or wear on the piston rings cause the compressor to hum but not create pressure. Freon simply flows from a high-pressure zone to a low-pressure zone, bypassing the condenser.
The connecting rod is attached to the shaft using a special coupler or bolt, which in some models can become loose due to vibration. This leads to knocking noise inside the compressor. If you hear a distinct metallic clanging sound when the engine is running, most likely the problem is in the crank mechanism. Repairing such a part at home is impossible due to the need for precise balancing and calibration of gaps.
☑️ Signs of wear on the crankshaft drive
Valve group and suction system
The upper part of the compressor unit is occupied by the head c valve plate. This is a thin steel piece with two holes closed by elastic petal valves. One valve is responsible for sucking freon gas from the evaporator, the second is responsible for pumping compressed gas into the condenser. The operation of the valves is synchronized with the movement of the piston: when the piston goes down, the suction valve opens, when up, the discharge valve opens.
The plates are made of special spring steel. Over time, the metal becomes tired and the valves can burn or become warped. If the valve does not fit tightly, the seal of the chamber is compromised. The compressor begins to run empty, trying to create pressure, which is immediately released back. Visually, this is manifested in the fact that both tubes (inlet and outlet) become warm, and cold does not appear in the chamber.
In some models, the valve system is supplemented with noise suppressors - small chambers or corrugated tubes that dampen gas pulsation. These elements are also located inside the casing or just outside it. Their damage leads to the appearance of a whistle or pulsating hum in the pipeline system.
The table below shows the main elements of the valve group and their functions:
| Element | Function | Frequent malfunction |
|---|---|---|
| Suction valve | Inlet of freon into the cylinder | Broken petal, leakage |
| Discharge valve | Outlet of compressed gas | Burning, loss elasticity |
| Valve plate | Base for attaching valves | Cracks, deformation |
| Valve spring | Returning the valve to its original position | Failure, loss of elasticity |
Oil system and lubrication
Without lubrication, the operation of the compressor would be impossible: friction of metal on metal at high speeds and temperatures would lead to jamming in seconds. Inside the casing there is a special mineral or synthetic oilthat does not harden at low temperatures and has high chemical stability. Oil is not just poured to the bottom, it actively circulates through the system.
At the lower end of the crankshaft there is often a helical slot or pump gear. As the shaft rotates, oil is captured and supplied through channels inside the shaft to the bearings and piston group. Part of the oil in the form of a fine suspension is carried away by the freon flow into the system, so modern refrigerators are equipped with oil separators that return the lubricant back to the compressor.
Is it possible to mix different oils?
It is strictly not recommended to mix mineral and synthetic oils, as well as oils from different manufacturers. The chemical reaction can lead to sediment that clogs the capillary tube, or to the formation of acids that corrode the motor windings from the inside.
If the oil level drops (for example, due to a freon leak that carries away oil mist, or depressurization of the system), dry friction begins. The shaft bearings are the first to suffer, then the piston scuffs. That is why, after any repair of the refrigerant circulation system (replacing the filter, capillary tube), it is often necessary to refill or replace the oil in the compressor itself, although in practice, technicians more often change the entire unit.
Typical malfunctions of internal components
Understanding what is inside the compressor from the refrigerator, you can logically deduce the causes of breakdowns. The most common is interturn short circuit motor windings. It occurs due to overheating or power surges. The engine hums, the hum may be different, but the start does not occur, the thermal protection relay is triggered.
The second most common problem is mechanical wear or jamming. If the compressor stood idle for a long time, oil could drain into the lower part, and corrosion could appear on the parts. When trying to start, the torque of the engine is not enough to break the shaft from its place. Sometimes a short-term supply of increased voltage helps, but this is a risky procedure.
⚠️ Attention: If the compressor is jammed, do not try to open it with a hammer by tapping the housing. This can damage the internal tubes or unbalance the engine mount, which will lead to even more noise.
The third reason is the destruction of the valve plate. Valve petals can break off and become lodged in the cylinder, causing the piston to strike metal debris. The sound in this case resembles the operation of a diesel engine or a hammer drill. Repair in this case does not make sense, since it is almost impossible to find an original valve group for a household hermetic compressor.
Is it possible to repair the compressor yourself
The question of repairing the “internals” of the compressor often arises among home craftsmen. Theoretically, if you carefully cut off the top cover of the casing (with a grinder or a hacksaw), you can gain access to the engine and piston group. However, sealing it back is a daunting task. It is impossible to weld the housing using argon welding at home, and brazing requires temperatures that can damage the internal insulation of the wires and the varnish coating of the windings.
In addition, for high-quality repairs you need a clean room. If one speck of dust gets between the piston and cylinder or into the valves, it will cause instant failure after starting. In the factory, assembly takes place under sterile conditions. Therefore, replacing internal parts (bearings, connecting rod) at home is a lottery with a low chance of success.
The only thing you can really do on your own is to replace the start relay or check the integrity of the windings through the contacts. If the problem is inside the casing, the most rational solution would be to purchase a new compressor of similar power and performance. This guarantees reliability and maintenance of the warranty for the remaining components of the refrigerator.
In conclusion, it is worth saying: the internal structure of the refrigerator compressor is a masterpiece of engineering, where everything is designed to the limit of the capabilities of materials. Careful handling of equipment, compliance with temperature conditions and timely defrosting will help prolong the life of this complex mechanism.
☑️ When a replacement is definitely needed
Why does the compressor get very hot during operation?
High casing temperature (up to 90 degrees) is the norm for many models, since the heat from engine operation and gas compression must go somewhere. However, if the temperature exceeds 110-120 degrees and the thermal relay is triggered, this may indicate a malfunction: a blockage in the system, a malfunction of the condenser fan, low voltage in the network, or wear and tear on the motor, which consumes increased current.
Is it possible to replace a compressor from a refrigerator with a similar one from another brand?
Yes, you can, but you need to observe several parameters: power (in BTU or W), refrigerant type (R134a, R600a), oil type and overall seat dimensions. It is also important to consider the type of trigger (RSIR, RSCR, CSIR). Compressor manufacturers (Danfoss, Secop, Embraco, LG) often have replacement cross-tables from which you can select an analogue.
How much oil should be inside the compressor?
The amount of oil depends on the model and volume of the system. Typically, household compressors contain from 150 to 300 ml of oil. The exact quantity is indicated in the technical documentation or on the nameplate. A lack of oil leads to jamming, and an excess leads to a drop in cooling capacity and clogging of the system with oil plugs.
What to do if, after replacing the compressor, the refrigerator does not freeze?
There may be several reasons: insufficient or excessive charging of freon, poor-quality evacuation of the system (air or moisture remains), blockage in filter drier or capillary tube, or leaking connections. It is also worth checking whether the tubes are connected correctly (input and output are mixed up), although this rarely happens.