When it stops being cold inside the refrigeration chamber and the unit makes strange sounds or, conversely, is silent, the first thing the owner remembers is the “heart” of the cooling system. In everyday life, this part is often called simply a motor, which is generally true, but technically not entirely accurate. The correct name of the key unit is compressor, and it is it that is responsible for the circulation of the refrigerant in a closed circuit, creating the necessary pressure for condensation and evaporation of freon.
Understanding how this unit works and works will help you quickly navigate when calling a specialist or trying to do it yourself diagnostics Many people confuse the electric motor, which is located inside the casing, with the compressor unit itself, although this is only part of a complex system. In this article we will take a detailed look at what it consists of motor-compressor, what types of devices exist and why knowing their differences is critical when selecting spare parts.
Do not underestimate the importance of accurate terminology when ordering repairs. If you tell the mechanic that your engine has “burned out,” he will understand what you mean, but in the spare parts catalogs you will find compressors of various modifications. Let's figure out why this unit fails and how to distinguish a motor breakdown from problems with the start relay or thermostat.
The official name and purpose of the unit
The technically competent name of the device that ensures the operation of the refrigerator is piston or linear compressor. Inside the sealed metal casing is an electric motor that drives a piston group or linear magnetic drive. It is the engine that converts electrical energy into mechanical energy, forcing the refrigerant to move through the tube system.
The main task of this unit is to create a pressure difference. On the one hand, it sucks low-pressure freon gas from the evaporator, and on the other, it pumps it into the condenser under high pressure. Without this process, heat exchange would be impossible, and the products in the chamber would quickly become unusable. Modern models can be equipped with inverter systems where the motor runs smoothly, without constant switching on and off.
⚠️ Attention: Attempting to open the sealed compressor casing at home is strictly prohibited. There may be oil under pressure inside, and the process itself requires special equipment for evacuation and filling.
It is important to distinguish between the concepts of “engine” and “compressor”. The motor is just the electrical part that turns the shaft. The compressor is the entire assembly, including the motor, cylinders, pistons, valves and housing. When purchasing a replacement part, you will always be offered the compressor, since the separate electric motor inside the casing practically does not change.
Design: what is inside the casing
Visually, the compressor is a black or gray metal cylinder (or “barrel”) located at the lower rear of the refrigerator. There is a vacuum inside this sealed housing, which is necessary for normal operation and to prevent oxidation of parts. Electric motor fixed on springs or rubber shock absorbers to dampen vibrations during operation.
The key elements of the internal structure are:
- 🔹 Stator and rotor —the main parts of the electric motor that create a rotating magnetic field.
- 🔹 Crankshaft —transmits rotation from the rotor to the piston group.
- 🔹 Pistons and cylinders —directly compress refrigerant.
- 🔹 Suction and discharge valves - regulate the movement of freon in the desired direction.
Outside, three tubes fit to the compressor housing: two copper (for freon inlet and outlet) and one steel (filler, which is sealed after assembly). Also located at the bottom start-protective block, which is often mistaken for part of the motor, although it is a separate electronic or mechanical part. It is this that supplies the initial impulse to start the rotor.
The rubbing parts are lubricated by oil, which is located at the bottom of the casing. When the engine is running, oil sprays out onto the bearings and cylinder walls. If the refrigerator stood in an inclined position for a long time, oil could drain into the circuit, which would lead to water hammer when first started. Therefore, after transportation, the unit must stand upright for at least 4-8 hours.
Types of compressors in modern refrigerators
Technology does not stand still, and today several types of engines can be found in refrigeration units. The most common option is piston compressor. It works on the principle of internal combustion, but in reverse: instead of expanding gases, it compresses them. Such motors are characterized by high maintainability and relatively low cost, but they create noticeable noise and vibration.
More modern models are equipped with inverter engines. Their main difference is the absence of a strict connection to on/off cycles. The inverter smoothly regulates the shaft rotation speed, maintaining the set temperature. This saves energy and significantly reduces noise levels. However, such systems are sensitive to voltage drops in the network.
There are also linear compressors, which are often found in LG equipment. There is no rotational movement in them; the piston moves back and forth under the influence of electromagnetic forces. This makes the design simpler and more reliable, but repair of such components often requires complete replacement, since they are less susceptible to overhaul.
| Compressor type | Noise level | Energy efficiency | Operating life |
|---|---|---|---|
| Piston | High | Medium | 10-15 years |
| Inverter | Low | High | 15-20 years |
| Linear | Average | High | 10-15 years |
| Oil-free | Low | Medium | 5-7 years |
Signs of a refrigerator motor malfunction
Determine that motor-compressor has failed can be determined by a number of characteristic signs. The most obvious is that the refrigerator has stopped freezing, but the light is on inside the chamber. If at the same time the compressor itself is silent and does not make any sounds, the motor winding may have burned out or the start relay has failed.
A frequent problem is when the motor tries to start, hums for a few seconds, then there is a click and it goes silent. After some time, the cycle repeats. This indicates that starting winding receives current, but the rotor cannot move. The reasons may be jamming of the piston group or breakdown of insulation.
Another alarming symptom is excessive heating of the compressor housing. If the “barrel” is hotter to the touch than 70-80 degrees, this may indicate an interturn short circuit or operation in overload mode. It is also worth paying attention to the color of the smoke (if it comes from the engine) - black smoke indicates burnt insulation, white smoke indicates oil ingress.
Why does it hum, but does not start?
Most often the reason is a jammed piston or a faulty start relay. The relay tries to give a starting impulse, but a mechanical obstacle prevents the shaft from turning. After a few seconds, the thermal protection is triggered and the motor stalls.
Diagnostics and performance testing
Before making a decision on replacement, it is necessary to carry out initial diagnostics. A multimeter is used to check the integrity of the motor windings. You need to remove the start-up relay and ring the contacts on the compressor housing. The normal resistance of the working winding is usually 10-30 Ohms, and the starting winding is 20-50 Ohms (depending on the model).
If the multimeter shows infinity (open) or zero (short circuit), the motor is faulty. It is also important to check whether the motor is “punching” into the housing. To do this, one multimeter probe is applied to any contact, and the second is applied to a stripped metal part of the case (for example, to a copper tube). The arrow of the device should not deviate.
In some cases, the problem lies not in the motor itself, but in thermostat or the temperature sensor. If the circuit is broken at the sensor, the signal to start the compressor simply does not arrive. Therefore, the check begins with an assessment of the electrical circuit as a whole, and not just the engine.
☑️ Motor diagnostics
Replacing the compressor: difficulties of the process
Replacement motor-compressor is a complex technical procedure that requires specialized tools. Simply “unscrewing and screwing” will not work here, since the system is sealed and filled with refrigerant. The process begins with pumping out the remaining freon and dismantling the old unit.
After installing the new compressor, it is necessary to solder the copper tubes. It is important not to overheat the soldering area so as not to damage the insides of the new motor. The system is then evacuated for 15-20 minutes to remove moisture and air. Only after this is freon charged in a strictly defined quantity, indicated on the refrigerator tag.
⚠️ Attention: Replacing the compressor yourself without a vacuum sealer and a pressure gauge station is almost guaranteed to damage the new unit. Moisture in the system will turn into acid, which will corrode the motor winding in a few months.
The cost of replacement work consists of the price of the compressor itself, the cost of the refrigerant, consumables and the work of the technician. It is often more economically feasible to replace the entire unit if the refrigerator is old, since a new compressor can cost up to 50-60% of the price of a new refrigerator.
Frequently asked questions (FAQ)
Is it possible to repair a burnt-out refrigerator motor?
At home - no. Rewinding the electric motor windings inside a sealed casing is impossible without factory equipment. Even in service centers, compressors are not repaired, but replaced entirely with new or refurbished analogues.
Why does a new compressor get hotter than the old one?
Modern motors often operate at higher temperatures to increase energy efficiency. In addition, if the vacuum was poorly carried out during replacement, residual air in the system causes overheating. Also, the cause may be an excess or lack of freon.
How do I know which motor is suitable for my refrigerator?
You need to look at the markings of the old compressor. Power, refrigerant type (R134a, R600a), oil type and overall dimensions are taken into account. There are no universal solutions; it is better to select an exact analogue by catalog number.
How long does a refrigerator motor last?
The average service life of a piston compressor is 10-12 years. Inverter models can operate for up to 20 years, provided there is a stable voltage in the electrical network. Sudden voltage surges are the main enemy of electronics and motor windings.