Sudden silence in the kitchen or, conversely, a loud knock and hum of a working unit often indicates a critical breakdown. Compressor is the heart of the refrigeration unit, and its failure leads to spoilage of food and the need for urgent intervention. Independent replacement of this unit requires not only technical skills, but also special equipment, since the system is sealed and under pressure.
Before proceeding with dismantling, it is necessary to accurately diagnose the malfunction, eliminating problems with the start relay or thermostat. If you are convinced that the motor-compressor hums, but does not start, or is completely silent when voltage is applied, and the windings are connected correctly, replacement becomes inevitable. It is important to understand that the work involves refrigerant and high soldering temperatures, which requires strict adherence to safety precautions.
In this article we will analyze the full cycle of work: from preparing the workplace to the final tightness check and filling the system with freon. A high-quality repair will extend the life of your Liebherr, Indesit or Atlant for many years. However, remember that any manipulations with the refrigerant must be carried out in a well-ventilated area.
Diagnostics and preparation for repair
The first step is always to accurately determine the cause of the failure. Do not rush to disassemble the unit if you have not carried out an initial check of the electrical circuit. Often it is not the motor itself that fails, but the starting protection relay or capacitor. Use a multimeter to test the windings: the resistance between the common contact and the working one, as well as between the common and the starting contact, should be within the normal range (usually 10-30 Ohms). If the resistance between the housing and the contacts shows a leak (less than 2 MOhm), the compressor must be disposed of, since its use is deadly.
If diagnostics have confirmed the need for replacement, prepare workspace. You will need easy access to the back of the refrigerator. Unplug the appliance and remove all products and shelves to lighten the structure. Move the refrigerator away from the wall at a sufficient distance, ensuring air circulation and ease of working with the blowtorch.
⚠️ Attention: Before starting work, be sure to make sure that there is no open flame (except for the burner) or sources of sparking in the room. Freon, when in contact with an open flame, can form toxic compounds.
To successfully complete the operation, you will need a specific set of tools. It is impossible to perform high-quality refueling without a vacuum pump and pressure gauge station, so renting or purchasing them is required. Also check the availability of a new compressor, which in terms of technical characteristics (power, refrigerant, oil type) fully corresponds to the original or is its approved analogue.
Necessary tools and materials
The quality of the repair directly depends on the equipment used. An attempt to replace the unit using improvised means will lead to repeated breakdown or ineffective operation of the refrigerator. The main tool will be a gas welding torch (propane-oxygen or propane-butane with an injector), which allows you to achieve the temperature necessary to melt the solder.
The list of required equipment includes not only a torch, but also means for creating a vacuum. Evacuation systems - a critical step that removes moisture and air that can cause blockage capillary tube or oil oxidation. You will also need a refrigerant charging kit with scales for accurate dosing of the gas mass.
- 🔧 Gas burner with a cylinder and a set of tips for soldering copper tubes of various diameters.
- 📉 Manometric station (manifold) with hoses for pumping out and refilling, compatible with your type of freon.
- ⚖️ High-precision electronic scales for weighing refrigerant when refilling.
- 🔌 Soldering materials: solder (silver or copper-phosphorus), flux, pipe cutter, extender pipes.
Pay special attention to consumables. Using the wrong solder can cause the connection to fail due to vibration. For copper tubing, copper-phosphorus solder, which does not require flux, is ideal, or silver solder for copper-steel joints. The pipe cutter must have a sharp, non-deformed wheel so as not to jam the thin walls of the capillary system.
⚠️ Attention: The characteristics of the refrigerant (R600a, R134a) determine the type of oil and safety requirements. R600a (isobutane) is explosive, which requires special care when soldering and ventilating.
Removing the old compressor
The removal process begins with access to the engine compartment. Remove the rear cover covering the unit. In some models, for example old Biryusa or Oka, it may be necessary to remove the back wall of the refrigerator compartment to access the soldering points. Before soldering, it is necessary to bleed the remaining refrigerant into the system or into a special collector if you plan to dispose of it environmentally.
The soldering area should be heated evenly. The burner flame is directed to the compressor tube and fitting. Once the solder has melted and become liquid, quickly pull back the torch and use pliers to release the joint. It is important not to overheat the tube itself, as this can lead to the formation of an oxide film inside, which will later clog the system.
After disconnecting the tubes (discharge, suction and possibly process), disconnect the electrical wires. Be sure to photograph or sketch the connection diagram so that when installing a new unit you do not mix up the contacts. Dismantle the compressor by unscrewing the mounting bolts or cutting off the shock absorbers if they are welded.
☑️ Preparation for dismantling
Inspect the dismantled unit. Often there are pieces of old solder left on the pipes that need to be carefully removed. If you are planning to install a new compressor of the same model, compare the geometric dimensions and location of the pipes. Sometimes a slight adjustment to the position of the unit or bending of the tubes for docking is required.
Installation of a new unit and soldering
Installation of a new motor-compressor begins with fixing it on the frame. Use original shock absorbers or quality replacements to minimize vibration and noise. Incorrect installation can lead to pipe breakage during operation due to resonance.
Soldering connections is the most critical stage. Clean the ends of the copper tubes and the inside of the fittings to a shine. Insert the tube into the fitting with a small gap (1-2 mm) necessary for solder to flow. Heat the joint evenly on all sides. When the copper reaches the desired temperature, bring the solder rod to the joint (not to the flame!).
The solder should melt from contact with the hot metal and fill the gap under the influence of the droplet effect. Avoid excess solder, which could flow into the tube and block the flow of refrigerant. After soldering, allow the joint to cool naturally without blowing water or air onto it to avoid thermal shock and cracks.
| Connection type | Solder material | Melting point | Features |
|---|---|---|---|
| Copper-Copper | Copper-phosphorus | 700-800°C | Does not require flux, high strength |
| Copper-Steel | Silver (30-40%) | 600-700°C | Requires flux, elastic |
| Aluminium | Special alloy | 550-600°C | Complex soldering, requires skills |
| Steel-Steel | Brass/Silver | 800-900°C | High temperature, risk of burning |
After all connections have been made, it is necessary to carry out pressure testing with nitrogen. This will allow you to identify microcracks or poor-quality soldering before refilling the system with expensive refrigerant. The pressure during pressure testing is usually 10-15 atmospheres, which is significantly higher than the operating pressure in the system.
Evacuation and refrigerant charging
Evacuation is the process of removing air and moisture from the refrigerator circuit. The moisture remaining in the system, at low temperatures, turns into ice plugs that block the capillary tube, and also reacts with the oil, forming an acid that destroys the windings. Connect the vacuum pump to the process pipe through the pressure gauge station.
Turn on the pump and monitor the pressure gauge readings. The needle should go into the vacuum zone (usually -1 bar or lower). Evacuation time depends on the pump power and system volume, but usually ranges from 30 minutes to 2 hours. For difficult cases or after a long period of inactivity of an open system, the procedure can be repeated: vacuum, let the system stand, and pump out the air again.
- 🌬️ Connect the vacuum pump to the blue hose of the pressure gauge station.
- ❄️ Open the valve at the station and turn on the pump for 40-60 minutes.
- 🔒 Close the valve, turn off the pump and watch the arrow: it should not rise.
Refrigerant is charged strictly according to the weight indicated on the refrigerator label (usually on the inner wall or back). Use electronic scales: place a cylinder with freon on the scale, reset the container and start supplying gas in the liquid phase (turning the cylinder over), if the type of refrigerant allows it, or in the gas phase, controlling the weight. For R600a refilling is often done with the compressor running through the suction pipe in gaseous form.
⚠️ Attention: Refilling accuracy is critical. A lack of freon will lead to poor cooling and overheating of the compressor, and an excess will lead to increased pressure, noise and possible rupture of the system or failure of the motor.
Checking performance and tightness
After refueling, turn on the refrigerator and let it run for 30-40 minutes. At this stage, it is important to monitor the temperature of the compressor housing (it should be warm, but not hot), the pressure in the system (it should correspond to the type of refrigerant and ambient temperature) and the operation of the evaporator.
Checking the tightness of all soldered seams is carried out using a soap solution. Apply thick foam to the solder joints and observe. The appearance of bubbles will indicate a leak. You can also use an electronic leak detector, which reacts to gas molecules in the air by giving an audible signal.
Evaluate the quality of cooling. A “coat” (frost) should begin to build up in the freezer compartment, and the temperature in the refrigerator compartment should drop. If the refrigerator operates cyclically (turns on and off according to the thermostat), then the system is functioning correctly. Long-term operation without shutting off may indicate a lack of freon or a leak.
Frequently asked questions (FAQ)
Is it possible to replace a compressor without a vacuum pump?
Theoretically, some craftsmen use the method of “squeezing out” the air with the refrigerant itself, purging the system several times. However, this method is considered artisanal and does not guarantee moisture removal. Moisture in the system is the main reason for the formation of acids and ice plugs, which will lead to repeated repairs after a few months. The use of a vacuum pump is a prerequisite for quality repairs.
Why does the new compressor hum loudly?
The hum can be caused by several reasons: incorrect installation (vibration is transmitted to the refrigerator body), a defect in the new unit itself (defect), or the presence of air in the system. The cause may also be water hammer if too much oil or liquid freon gets into the system during refueling. Check the fasteners and shock absorbers.
Which solder is best to use for soldering?
Copper-phosphorus solder (for example, PSr-15 or imported analogues) is optimal for connecting copper tubes to each other, since it does not require flux and has good fluidity. To solder copper to steel (compressor fittings), you need silver solder (with a silver content of 15% to 40%) and a special flux for steel. The use of tin-lead solders (PLS) in refrigeration systems is prohibited due to low strength and melting point.
How long does it take to vacuum the system?
The minimum vacuum time is 30 minutes for small systems. However, to completely remove moisture, especially if the system has been open for a long time, it is recommended to carry out the procedure for 1-2 hours. The end criterion is the stable position of the pressure gauge needle in the vacuum zone after turning off the pump for 15-20 minutes.
Is it dangerous to change the compressor yourself?
Yes, it is fraught with risks. The main dangers are: burns from open flames and hot pipes, electric shock (220V), risk of explosion (when working with R600a) and poisoning from freon combustion products. In addition, improper soldering or refilling can lead to permanent failure of the refrigerator. If you do not have experience in gas welding work, it is better to entrust this to professionals.