Failure of a compressor is often the most expensive a breakdown in the refrigerator, but it does not always mean the final death of the unit. Sometimes the problem lies in the degradation of the lubricant, which has lost its properties due to prolonged use or overheating. Changing the oil in a refrigerator compressor can bring the device back to life if mechanical parts, such as pistons and valves, are not critically worn.
Many technicians immediately recommend replacing the entire assembly, arguing that opening it breaks the seal. However, for an experienced home craftsman or repair specialist, such a procedure is quite feasible if you have a vacuum pump and strictly adhere to the technology. It is important to understand that reigns inside the system absolute cleanliness, and the ingress of even microscopic dust or moisture can lead to re-acidification in a short time.
Before starting work, you must clearly understand the risks. An incorrectly selected brand of oil or poorly carried out evacuation will lead to the fact that the refrigerator will stop freezing and the compressor will burn out in a matter of hours. This article will help you understand the intricacies of the process, choose the right chemistry and do the job professionally.
Diagnostics: when you really need an oil change
A humming or poorly functioning refrigerator does not always require a lubricant change. The first sign of the need for maintenance is a change in the color and consistency of the fluid that flows out when the system is depressurized. If, instead of a transparent or slightly yellowish substance, you see a black, thick mass with a burning smell, then mineral oil it has completely exhausted its resource.
Often, replacement is required after the system has acid breakdown windings of the electric motor. In this case, the combustion products of the insulation are mixed with the lubricant, turning it into an aggressive environment that corrodes varnish coatings and rubbing vapors. Also, the cause may be long-term idleness of the equipment, when the oil oxidizes upon contact with residual air.
It is worth paying attention to the noise during operation. If the compressor hums louder than usual, knocks or vibrates, this may indicate oil starvation. However, before disassembling, make sure that the problem is not vibration of the housing or improper installation of the unit.
Choosing the right oil for the compressor
The most critical point in the whole process is choosing the right lubricant. Modern refrigerators use three main types of oils: mineral, alkylbenzene and synthetic based polyesters (POE). Using the wrong type will lead to rapid failure of the compressor.
For older models running on R12 freon, mineral oils were traditionally used. They are cheap and available, but have one significant drawback - low hygroscopicity, that is, the ability to absorb moisture. For modern systems with freon R134a and R600a, where synthetic oils are used, moisture is a mortal enemy.
Below is a table of correspondence between types of oils and refrigerants so that you do not make a fatal mistake when choosing:
| Refrigerant type | Recommended oil type | Features | Examples of brands |
|---|---|---|---|
| R12 (Freon-12) | Mineral | Not hygroscopic, afraid moisture | HF 12-16, Suniso 3GS |
| R134a | Synthetic (POE) | Highly hygroscopic, aggressive to rubber | Polyol Ester, Mobil EAL |
| R600a (Isobutane) | Synthetic (POE) / Mineral | Depends on the compressor model | Danfoss POE, Embraco |
| R404A / R507 | Synthetic (POE) | Used in industrial refrigeration | Friga-Bohn, Bitzer |
Please note that synthetic oils are polyester based (Polyol Ester) are highly hygroscopic. They absorb moisture from the air literally before our eyes. Therefore, the can of oil must be opened immediately before filling.
Necessary tools and workplace preparation
For a high-quality oil change, it is not enough just to have a screwdriver and a funnel. You will need specialized equipment that will provide the necessary vacuum preparation for the system. Without a vacuum pump, it is pointless to take on this work, since you will not be able to remove moisture and air from the inside.
You will need the following tools:
- ⚙️ Vacuum pump (two-stage is preferable) for deep pumping.
- ⚙️ Manometric station with a vacuum gauge to monitor pressure.
- ⚙️ Large-volume syringe or special filling cylinder.
- ⚙️ Gas torch or torch for soldering copper pipes.
- ⚙️ Solder and flux for sealing nozzles.
Prepare a clean, well-lit place. It is better to remove the compressor from the refrigerator and turn it over so that access to the pipes is convenient. Prepare containers in advance for draining the waste liquid, as it can be toxic.
⚠️ Attention: Work with soldering and refrigerants requires compliance with fire safety rules. Make sure that there are no open sources of fire in the room, except for your burner, and good ventilation is provided.
☑️ Preparing for an oil change
Technology for draining old oil
The process of removing used oil Lubrication begins with sealing the suction pipe to create pressure inside the housing. To do this, you can use a plug or simply clamp the tube if it is copper and allows this. Then the compressor is turned on for a short time (literally 30-60 seconds) to build up pressure.
After turning off the power, the discharge pipe is quickly unscrewed or cut off. Under pressure, residual oil and gases will escape. Be prepared to collect this stream in a prepared container. Avoid splashing, as the oil may contain acidic residues.
To completely remove the liquid, the compressor must be tilted in different directions.
- 📉 Tilt the unit to the right and wait until the oil flows to the hole.
- 📉 Turn the compressor upside down (be careful not to damage the internal suspension).
- 📉 Shake the housing to expel liquid from hard-to-reach cavities.
Some technicians recommend purging the system with dry nitrogen to displace the remaining old lubricant. This is especially true if the windings burn. However, at home, it is enough to thoroughly shake out the compressor.
If the old refrigerant was still in the system, it must be released in a well-ventilated area or outside. Freons are heavier than air and can displace oxygen, creating a risk of suffocation in a confined space.
Flushing the system and removing moisture
You cannot simply fill in new oil - remnants of the old one and decay products can mix with it and spoil it. Flushing is carried out with a special flushing solvent or the same type of oil that you plan to fill. The liquid is poured inside, the compressor is shaken several times, and the solution is drained.
The most important stage is evacuation. Moisture is the main enemy of the compressor. As the compressor operates, it heats up and if there is water inside, it will turn into steam, creating pressure and damaging the lubrication. The vacuum pump is connected to the pipes, and the system is pumped out until a deep vacuum is achieved.
⚠️ Attention: The vacuuming process should last at least 30-40 minutes. Short-term pumping will not remove moisture absorbed into the walls and windings of the motor.
During pumping, you can slightly warm the compressor housing with a hairdryer (not open fire!) to speed up the evaporation of moisture. The heating temperature should not exceed 60-70 degrees Celsius so as not to damage the varnish insulation of the wires.
Why can’t you use car compressors for vacuum?
Car pumps create pressure, but not vacuum. To pump air out of the refrigeration system, you need a special pump capable of creating a residual pressure of several microns. A conventional pump will leave moisture and air inside, which will kill the compressor.
Filling new oil and assembly
After achieving the required vacuum, without turning off the pump, you must carefully fill in new oil. This is done through the suction pipe using a syringe or through a special filling valve. The volume of oil is strictly regulated by the manufacturer and usually ranges from 150 to 250 grams, depending on the model.
To accurately determine the amount, it is best to weigh the compressor before and after filling. The difference in weight must correspond to the passport data. Overfilling the oil will lead to water hammer and increased pressure in the system, and underfilling will lead to overheating.
Procedure for refueling:
- 🛢️ Measure the exact volume of oil (for example, 200 ml).
- 🛢️ Quickly open the container with oil to minimize contact with air.
- 🛢️ Pour oil into the compressor through a funnel or syringe.
- 🛢️ Immediately plug the pipes so that moist air does not get inside.
After filling, the pipes are sealed. It is important to do this quickly so that the compressor does not have time to draw moisture from the atmosphere. Soldering is done with silver solder, which ensures a reliable and tight connection.
Startup and performance check
After installing the compressor in place and connecting it to the power supply (without connecting to the refrigerator system yet), a test run is performed. The unit should operate smoothly, without knocking, vibration or excessive heating. The body should be warm to the touch, but not hot.
Check the outlet pressure. It must correspond to the characteristics of the model. If the compressor operates normally for 10-15 minutes, you can proceed to connecting it to the evaporator and condenser of the refrigerator. After this, the system is evacuated again and charged with freon.
During the first hours of operation, carefully monitor the body temperature. If the compressor begins to overheat or switches off by the thermal relay, it means that there is air left in the system or the wrong oil has been selected. In this case, the procedure may have to be repeated.
Is it possible to mix different types of oils?
It is strictly not recommended. Mixing mineral and synthetic oils can cause sediment to form, which will clog the capillary tube. If you do not know what was filled previously, it is better to thoroughly flush the system with a solvent before filling a new type.
How much oil is needed for a refrigerator compressor?
The volume depends on the power and model of the compressor. Typically, household compressors require from 120 to 250 grams. Precise information can be found in the technical documentation or on the manufacturer's website (e.g. Danfoss, Embraco, Secop). Overfilling is more dangerous than underfilling.
Why did the compressor jam after changing the oil?
There may be several reasons: moisture getting inside, using the wrong type of oil, mechanical wear of parts that was not immediately noticeable, or the presence of debris in the system. It is also possible that jamming occurred due to water hammer with excess oil.
Where can I get a vacuum pump for a one-time replacement?
Vacuum pumps can be rented from specialized refrigeration equipment stores or from private craftsmen. Buying a new pump for a one-time replacement may not be economically feasible, since the cost of the equipment is high.