Failure of a compressor is perhaps the most unpleasant scenario for the owner of a refrigerator, since this unit is the “heart” of the entire cooling system. When the equipment stops freezing or begins to work intermittently, the issue of replacing the main unit becomes critical, because the future fate of the device depends on the correct choice. An error in selection can lead to the fact that the new motor-compressor will burn out after a few hours of operation or will not effectively cool the chamber.
The modern market offers many options, from original spare parts to universal analogues, which often confuses the master. It is necessary to take into account not only the overall dimensions, but also the type of refrigerant, the volume of the fridge compartment, the power and starting characteristics of the engine. In this article, we will analyze in detail all the technical nuances that will help you make the right decision and avoid costly mistakes during repairs.
Diagnostics of the compressor condition before replacement
Before going to the store for spare parts, you need to make sure that the problem lies in the compressor, and not in the thermostat, start relay or leakage freon. Symptoms of a malfunction can be different: from complete silence of the unit to continuous humming without starting the engine. Often, equipment owners mistakenly blame the motor, when in fact the capillary is clogged or the temperature sensor is faulty.
Primary diagnosis includes a visual inspection and listening to the operation of the device. If the compressor hums but does not start, and after a while a click is heard and the hum stops, this may indicate a jammed piston group or a failure of the start relay. In a situation where the motor is constantly running, but the temperature in the chamber does not drop below +10 degrees, we may be talking about a loss of valve performance or a refrigerant leak.
For a more accurate check, professionals use a multimeter to test the windings. Normal resistance between the working and starting terminals, as well as between them and the housing (where there should be no resistance) is the first sign of serviceability of the electrical part. However, even a serviceable winding does not guarantee that the mechanical part motor-compressor functions correctly.
⚠️ Attention: If you hear a metallic knock or grinding sound when you try to start, this is a sure sign of mechanical destruction of the internal components. Such a unit cannot be operated, since wear products can enter the system and clog the filter drier.
It is also worth checking the start relay, since it is often the cause of the “death” of the compressor. A burnt winding or a jammed piston may be a consequence of working with a faulty relay, so replacing just the motor without checking the periphery may not be economically feasible.
Basic parameters for selecting an analogue
Selecting a compressor is not just a search for a model with a similar name, but a complex engineering process that requires taking into account many parameters. The most important criterion is cooling capacitywhich must correspond to the volume of the refrigerator and freezer compartments. If you install a motor of less power, it will work hard, trying to reach the set temperature, which will lead to rapid overheating and failure.
The second critical parameter is the type of refrigerant used. Modern refrigerators operate on different freons, such as R134a, R600a (isobutane) or outdated R12. Compressors designed for one type of gas may have different oils and design features, so their interchangeability is limited or impossible without completely flushing the system.
Overall dimensions and mounting holes also play a decisive role. The compressor must physically fit into a niche on the back wall of the refrigerator, and its pipes must match the diameter and location of the condenser and evaporator pipes. Often you have to use adapters or additionally bend copper tubes, which requires skills in working with metal.
Do not forget about power consumption and starting current. These characteristics must correspond to the capabilities of the electrical wiring and starting fittings installed in the refrigerator. Exceeding the rated values can lead to melting of the relay contacts or even a fire.
Why can’t you install a more powerful compressor?
Installing a larger compressor may seem like a good idea, but it is dangerous. The tube system, condenser and evaporator are designed for a certain pressure and volume of circulating gas. Excessive power will lead to increased pressure in the system, overloading the condenser and possible rupture of thin-walled evaporator elements. In addition, the thermostat may incorrectly turn off an overly powerful motor.
Compatibility of refrigerants and oils
One of the most common mistakes during self-repair is ignoring the type of refrigerant. Each type of freon requires the use of specific compressor oil, which provides lubrication of rubbing parts and effectively circulates through the system along with the gas. Mixing different types of oils or using the wrong refrigerant can lead to the formation of acids, blockage of the capillary tube and complete system failure.
Refrigerant R134a (tetrafluoroethane) is the standard for most modern refrigerators. It works in tandem with polyester oils (POE), which are highly hygroscopic, that is, they actively absorb moisture from the air. Therefore, when replacing a compressor on such a system, it is necessary to minimize the open circuit time and be sure to change the filter drier.
Freon R600a (isobutane) is becoming increasingly popular due to its environmental friendliness and energy efficiency. However, this is an explosive gas, which imposes special requirements on the tightness of the system and the qualifications of the technician. Compressors for R600a often have a smaller cylinder volume and operate at lower pressure, but their starting currents may differ.
To understand compatibility, below is a table of correspondence between types of refrigerants and oils:
| Refrigerant type | Oil type | Features | Application |
|---|---|---|---|
| R12 (Freon-12) | Mineral (MO) | Outdated, destroys the ozone layer | Old Soviet and imported refrigerators |
| R134a | Polyester (POE) | Hygroscopic, requires careful vacuuming | Most modern refrigerators (No Frost and static) |
| R600a | Mineral (MO) | Explosive, small amount of filling | Economical models, built-in appliances |
| R404A | Polyester (POE) | High pressure, low temperatures | Chest freezers, industrial equipment |
⚠️ Attention: It is strictly forbidden to mix mineral and synthetic (polyester) oils. This leads to the formation of sediment, which tightly clogs the capillary tube, making repairs almost impossible without completely disassembling the system.
When switching from one type of refrigerant to another (for example, when replacing an old R12 with a modern analogue), a complete flushing of the system with nitrogen and replacement of all elements in contact with the oil, including condenser, if it cannot be properly washed.
Calculation of power and cooling capacity
Correct calculation of power is the key to the longevity of the repaired refrigerator. The cooling capacity of a compressor is measured in watts (W) or kcal/hour and depends on the boiling point of the refrigerant. The device nameplate usually indicates values for standard conditions, for example, at a boiling point of -23.3°C or -26.1°C (ASHRAE standard).
For household selection, a simplified method is often used: the volume of the refrigerator compartment is multiplied by a coefficient depending on the type of refrigerator. For single-chamber models, this coefficient is lower than for two-chamber models with a No Frostsystem, where intensive cooling of the evaporator is required. Lack of power will lead to the fact that the refrigerator simply will not be able to reach the operating mode and will work around the clock.
It is also important to take into account the climate class of the equipment. If the refrigerator is designed for a temperate climate (SN, N), and you live in a hot region, the standard compressor may not be enough even in good condition. In such cases, it is permissible to install an analogue with a cooling capacity 10-15% higher than the original, but only if the remaining elements of the system are compatible.
The energy efficiency of the new compressor is also important. Modern inverter models or A++ class motors consume significantly less electricity than older counterparts, however, their installation requires replacing the control unit, since they are not compatible with standard starting relays.
☑️ Checking power compliance
Installation and connection instructions
The process of replacing the compressor requires special tools: a pipe cutter, a rolling machine, a vacuum pump and a pressure gauge station. Simply “unscrewing and screwing” will not work here, since the system must be absolutely sealed. The first step is to carefully remove the old compressor, heating the soldering points with a torch, so as not to damage the heat exchanger tubes.
After dismantling, the system is pressurized with nitrogen to search for leaks, if the cause of the breakdown has not been accurately diagnosed earlier. Then a new filter drier is installed, which is always changed once. The compressor is fixed on shock absorbers, after which the connecting tubes are rolled and soldered. When soldering, it is important not to overheat the compressor housing, so the pipes should be held with a damp rag.
The key stage is evacuation of the system. Vacuum pump should work for at least 15-20 minutes to remove air and moisture vapor from the circuit. The residual pressure should be about 200-300 microns. Without this step, the moisture remaining in the system will freeze in the capillary tube and block the circulation of freon.
Refrigerant charging is carried out strictly according to the weight indicated on the refrigerator's factory tag. The use of a cylinder with scales or a graduated cylinder is mandatory, since excess or lack of freon is equally harmful to the compressor. After refueling, the motor current consumption is checked with an ammeter.
⚠️ Attention: Technical characteristics and installation requirements may vary depending on the equipment manufacturer. Always check the official service documentation for your refrigerator model before starting work.
Common mistakes when choosing and replacing
One of the main mistakes is trying to save money and buy a used compressor from disassembly. The service life of such devices is unknown; they may have wear out in the cylinder-piston group or hidden defects in the windings. Considering the laboriousness of replacement, savings of several thousand rubles do not justify the risk of repeated repairs in a month.
The second common mistake is ignoring the replacement of the filter drier and the starting relay. An old relay may have changed characteristics and not ensure the correct start of a new motor, and the old filter will no longer be able to effectively remove moisture, which will lead to corrosion of the internal parts of the compressor from the inside.
Also, craftsmen often forget about the correct disposal of old refrigerant. The release of freon into the atmosphere not only harms the environment, but also violates safety regulations, especially when it comes to flammable gases. All work should be carried out in a well-ventilated area away from open flame sources.
Do not try to start the compressor directly, bypassing the protective relay, for “checking”. This can lead to the windings burning out when jammed, since the thermal protection will not operate in time. Diagnostics should be carried out using safe methods.
Is it possible to use a compressor from an air conditioner in a refrigerator?
Theoretically it is possible, but it is extremely difficult. Air conditioning compressors operate at different pressures, often use three-phase power or inverter control, and have different seat sizes and types of oils. Remaking the system for such a unit will require a complete replacement of the capillary tube, condenser and control unit, which is not economically feasible.
Questions and answers (FAQ)
Is it possible to replace an R12 compressor with an R134a without flushing the system?
No, it is not possible. Oils for these refrigerants are not compatible. The mineral oil from R12 will mix with the polyester oil of the new compressor, form an emulsion and clog the system. A complete nitrogen flush or replacement of the condenser and evaporator is required.
Why does the new compressor get hotter than the old one?
A slight increase in temperature is normal for modern high-efficiency models. However, if the housing is hot to the point where you cannot touch it with your hand, this may indicate a lack of refrigerant, air in the system or a malfunction of the condenser.
How much does it cost to replace a compressor in a service compared to doing it yourself?
Independent replacement saves the cost of the technician’s work, but requires the purchase of an expensive tool (vacuum unit, burner, pressure gauges), which will pay off only with multiple repairs. For a one-time replacement, it is more profitable to call a specialist.
Does the inverter compressor hum during operation?
Inverter compressors operate much quieter than usual, since they do not have sudden starts and stops. They change speed smoothly. A strong hum or vibration is not typical for them and indicates a malfunction or improper fastening.
Do I need to wait before turning it on after replacement?
Yes, after transportation and installation the compressor should stand in a vertical position for at least 2-4 hours (preferably a day). This is necessary so that the oil flows into the crankcase and does not enter the circuit during the first start-up, which can cause water hammer.