How to lubricate a refrigerator compressor: a step-by-step guide

The appearance of extraneous noise, hum or knocking during the operation of the refrigeration unit the unit often indicates that the rubbing parts do not have enough lubrication. Many owners of household appliances immediately think about buying a new device, but in some cases the situation can be corrected if it is properly serviced compressor. This is the heart of the refrigerator, which requires careful handling and strict adherence to maintenance technology.

The lubrication process is not a standard procedure that can be performed simply by opening the door, as during defrosting. This is a complex technical operation that requires an understanding of the operating principles sealed unit and the availability of specific tools. If you approach the matter without preparation, you can irreversibly damage the equipment, so you must strictly follow the algorithm of actions.

In this article we will look in detail at how to determine the need for lubrication, what materials to use and how to carry out the procedure with minimal risk to the equipment. It is important to understand that modern models often cannot be repaired at home, but knowledge of the nuances will help extend the life of old but reliable devices.

Diagnostics: when a compressor needs lubrication

The first sign that motor-compressor is experiencing oil starvation is a change in the nature of its operation. If previously the refrigerator hummed smoothly and quietly, but now it makes sounds reminiscent of metal rubbing against metal, or makes an intermittent hum, this is an alarming signal. It is also worth paying attention to the heating of the unit body - if it heats up to very high temperatures, this may indicate increased friction of internal parts.

There are several indirect signs that may confirm the need for technical intervention:

• 🔊 The appearance of a metallic knocking or grinding sound when starting and stopping the engine.
• 🔥 Strong heating of the rear wall of the refrigerator in the area of the motor.
• ❄️ Deterioration in the quality of freezing with a working thermostat.
• 🔌 Frequent attempts to start followed by a click and shutdown (the thermal relay).

However, before starting repairs, you need to make sure that the problem is mechanical wear and not a malfunction of the electrical part. Sometimes a hum can come from a fan or rattling tubes that are simply touching the housing. Careful diagnostics helps to avoid unnecessary opening of the system.

⚠️ Attention: If the compressor runs dry for too long, scuffing may form on the piston group. In this case, simple lubrication will no longer help, and a complete replacement of the unit will be required.

Check whether the condenser is clogged with dust, since overheating is often confused with a lack of lubrication. If the radiator is clean and the sounds continue to increase, most likely the oil in crankcase has exhausted its service life or its level has dropped critically.

Choosing the right oil for the compressor

The most critical mistake during maintenance is the use of unsuitable lubricants. Refrigeration compressors use a special oil that has unique properties: it must not freeze at low temperatures and must be chemically inert to the refrigerant. Regular machine oil is absolutely not suitable, as it can coagulate or react with freon.

The type of oil required directly depends on the type of refrigerant charged into the system. If your refrigerator uses R-12 freon, then mineral oil is needed. For modern refrigerants, such as R-134a or R-600a, synthetic polyester oils (POE) are used. Mixing these types of oils is unacceptable, as this will lead to the formation of acid and destruction of the insulation of the motor windings.

Below is a table of correspondence between oils and types of refrigerants, which should be used as a guide when choosing:

When purchasing oil, pay attention to the viscosity. Typically, oils with a viscosity of 16 to 32 cSt at a temperature of 40°C are suitable for household refrigerators. Using too thick oil will make it difficult to start the engine, especially at low temperatures, and too thin will not provide the necessary film film between the rubbing parts.

Necessary tools and preparation

To carry out high-quality lubrication, you will need not only the oil itself, but also specialized tools. Without it, it will be impossible to penetrate inside the sealed housing and introduce lubricant. The main tool is a syringe with a long needle or a medical system (dropper), which will allow you to dose the liquid to the desired point.

You will also need:

• 🛠️ A set of open-end or adjustable wrenches for dismantling the protective casing.
• 🔧 Screwdrivers (cross and flat) for removing fasteners.
• 🧤 Gloves and rags to protect hands and clean surfaces from dirt.
• 🧪 A container for collecting the remaining old oil if you plan to partially replace it.

Before starting work, be sure to disconnect the refrigerator from the power supply. This is a basic rule electrical safety, ignoring which may result in electric shock. Let the unit stand unplugged for at least 15-20 minutes so that the pressure in the system has time to equalize and the capacitors to discharge.

Organize good lighting in the work area. You will be working with small parts and thin tubes, so poor light can cause errors. Prepare in advance a place where you can lay out the tools so as not to look for them while working.

⚠️ Attention: If you plan to open the system (unsolder the tubes), you will need a torch and soldering skills. However, the method of adding oil through a drilled hole is less invasive, but requires care.

Lubricating technology without opening the system

There is a way to add oil to the compressor without breaking the tightness of the freon circuit. This method is effective if there is still some oil left in the system, and you just need to add fresh oil to reduce friction. The essence of the method is to introduce lubricant through the technological hole or through a capillary tube, if there is access.

Find the suction tube on the compressor body (usually it is thicker than the discharge tube and does not heat up during operation). Carefully bend its end or, in rare cases, make a puncture with a thin drill (about 2 mm in diameter) directly in the body, if the design allows. Insert the needle of a syringe filled with oil and slowly squeeze out the contents. This should be done in portions, allowing the oil to spread throughout the internal cavities.

After introducing the oil, you need to let the compressor run. Turn on the refrigerator for a short time (1-2 minutes) so that the piston group captures the new lubricant and distributes it among the components. Then turn it off again and repeat the procedure if necessary. After completing all manipulations, the puncture site must be carefully sealed.

To seal a puncture, it is best to use cold welding or a special sealant that is resistant to oils and vibrations. Regular silicone will not work here, as it may not withstand pressure or temperature. Make sure that seal is done well to prevent oil vapor leakage in the future.

Lubrication through dismantling the unit

If simple topping up is not enough or a complete oil change is required, the compressor will have to be removed. This is a more labor-intensive process that requires disconnecting the tubes. First, you need to bleed off the refrigerant (at home, this is done carefully by puncturing it, observing safety precautions, since the gas can be flammable). Then the tubes are cut or unsoldered.

The removed compressor is turned over and the remaining old oil is drained through the technological holes. There are usually three of them: for suction, discharge and process. It is most convenient to wash and fill through the technological hole, which is often closed with a plug. Flushing is done with a special solvent for refrigeration systems or the same type of fresh oil.

The process of pouring new oil is as follows:

1. Turn the compressor over so that the technological hole is on top.
2. Using a funnel or syringe, fill in the calculated amount of oil (usually 150-200 grams, the exact weight is indicated in the passport).
3. Rotate the engine shaft manually (if possible) or shake the housing slightly so that the oil gets into all corners.
4. Close the hole with a temporary plug and check the compressor on the stand before installation.

Is it possible use motor oil?

In emergency cases, to extend the life of an old refrigerator for a couple of months, some craftsmen use high-viscosity synthetic motor oil. However, this is “death” for the system in the long term, since it may not mix with freon and clog the capillary.

After changing the oil and checking the performance in air, the compressor is installed in place. The tubes are sealed, the system is evacuated and filled with freon. Without evacuation, moisture will remain in the system, which, when frozen, will block the capillary, and the refrigerator will stop cooling.

Common mistakes and precautions

When doing self-repair, it is easy to make a mistake that will be fatal for the equipment. One of the most common problems is moisture getting inside the system. Moisture combined with oil and electricity creates an aggressive environment that destroys insulation windings. Therefore, all work must be carried out in a dry room, and the tools must be clean and grease-free.

Another mistake is overfilling the oil. If you fill more than normal, excess oil will enter the condenser and evaporator, sharply reducing the efficiency of heat transfer. The refrigerator will work, but not freeze. In addition, liquid oil can enter the compressor cylinder, causing water hammer, which will destroy the valves.

⚠️ Attention: Never turn on the compressor if the suction or discharge pipes are open and not connected to the system. This can lead to oil splashing and valve damage due to lack of back pressure.

It is also important not to mix up the tubes. The suction tube is usually of a larger diameter, and the discharge tube is of a smaller diameter. If they are connected incorrectly, the compressor will not create the necessary pressure and freon circulation will be impossible. Carefully study the diagram before starting soldering.

Completion of work and testing

After all manipulations are completed, the compressor is installed and the tubes are sealed, The testing stage begins. Plug in the refrigerator and listen to the startup sound. It should be smooth, without clanging or grinding. In the first minutes of operation, an increased hum is possible, as the oil is distributed throughout the system, but then the sound should stabilize.

Check the temperature of the compressor housing after 30-40 minutes of operation. It should be hot, but not scalding. If the temperature is critical, the oil may still be low or circulation may be impaired. Also check the tightness of the connections using a soap solution - apply foam to the solder joints and make sure that bubbles do not inflate.

Complete restoration of cooling capacity may take several hours. Do not load the refrigerator with food immediately, let it get into operating mode. If after 2-3 hours the inside of the chamber has not become colder, perhaps the problem was not only in the lubrication, or the tightness of the circuit was broken.

How long does the compressor last after repair?

The service life of the repaired compressor depends on the degree of wear before the intervention. In the best case, it can last another 3-5 years, but often such repairs are considered a temporary measure.

Regular maintenance and timely replacement of filters (if your model has them) will help extend the life of the unit. Remember that prevention is always cheaper and easier than complex repairs.

Is it possible to lubricate the compressor without removing it from the refrigerator?

Yes, this is possible by topping up through a puncture in the suction tube or through a technological hole, if there is access. However, this method does not allow replacing old oil, but only adding fresh one.

Which oil is better: mineral or synthetic?

The choice depends solely on the type of refrigerant. For R-12 you need mineral, for R-134a and R-600a you need synthetic (POE). They cannot be mixed.

Why does the compressor hum even after lubrication?

Perhaps the wear of the bearings or valve group has already become critical, and the lubricant cannot compensate for the mechanical gaps. Also, the cause may be incorrect installation or vibration of the case.

Is it dangerous to open the refrigerator system yourself?

Yes, it is dangerous. There may be pressurized gas inside which can ignite if not handled correctly (especially isobutane). There is also a risk of frostbite on your hands upon contact with the escaping gas.