A sudden stop of the refrigerator is always stressful, because food supplies are at risk. Most often, the cause of a complete loss of cold is a failure compressor, which is the heart of the entire cooling system. If the unit hums, but does not cool, or is silent and does not start, despite working electronics, it will most likely need to be replaced.
The replacement process motor-compressor is technically complex and requires special tools, but for experienced craftsmen this is a standard procedure. In this article we will look at how to correctly diagnose a malfunction, select an analogue and perform a replacement, observing all the technological nuances of working with the refrigeration circuit.
It is worth immediately noting that replacing a compressor is not just “unscrewing and screwing”. This is work with a sealed circuit, requiring evacuation and precise dosage of refrigerant. If you have never held a burner and a pressure manifold in your hands, it may be worth turning to professionals, but if the goal is to study the theory or you have the skills, let's figure it out.
Diagnostics and signs of compressor malfunction
Before buying a new part, you need to make sure that the problem lies with it, and not with the start relay or thermostat. Symptoms can be different: from complete silence of the unit to characteristic clicks when trying to start. Often the compressor tries to start, hums for a few seconds, and then a click is heard and it goes silent again.
For an accurate check, you need to ring the motor windings with a multimeter. Normal resistance between contacts is usually between 20 and 40 ohms, depending on the model. If the device shows break (infinity) or short circuit (zero or close to zero value), then the part is clearly faulty and requires replacement.
⚠️ Attention: If the compressor is heated to a very high temperature (more than 90 degrees) and does not start, this may indicate an interturn short circuit. It is dangerous to touch such parts with bare hands - let the unit cool completely before diagnosing.
It is also worth checking the starting relay. Sometimes the motor itself is fine, but the relay cannot supply the required impulse to start. Remove the relay, shake it: if you hear the ringing of internal parts, it means the mechanism is destroyed. Replacing the relay is an inexpensive and simple procedure; it often solves the problem without replacing the main unit.
Selecting a new compressor and preparing tools
Selecting a new unit is a critical stage. Compressors differ in power, type of refrigerant (R134a, R600a), overall dimensions and type of fastening. The ideal option is to find the original model using the catalog number stamped on the nameplate of the old motor. If the original cannot be found, one is selected analogue with similar characteristics.
Pay special attention to the type of refrigerant. If your refrigerator ran on R600a (isobutane), then the new compressor should be designed for this gas. Isobutane is explosive, so using unsuitable equipment or violating the filling technology can lead to serious consequences.
To carry out the work, you will need a specialized tool, without which a high-quality replacement is impossible. The list of necessary equipment includes:
- 🔥 Gas torch with a cylinder (for soldering copper tubes).
- 🔧 Pipe cutter and rolling machine (for preparing copper connections).
- 📏 Manometric manifold and vacuum pump (to create vacuum and refills).
- ⚖️ Electronic scales (for accurate weighing of freon).
You will also need solder for copper (usually rods with a silver content of 5-15% or phosphorus-containing solders) and flux. The use of tin for soldering high-pressure copper pipes is strictly not recommended, since such a seam may not withstand vibration and pressure.
Is it possible to use a compressor from another brand?
Yes, you can if the mounting dimensions, power and type of refrigerant are the same. However, it is important to check the diameter of the fittings: they may differ between different manufacturers, and then you will have to digest or resolder the suction and discharge tubes using adapters.
Removing the old compressor
The first step is always to completely disconnect the refrigerator from the power supply. Then the unit must be moved away from the wall and access to the rear is provided. Remove the protective cover covering the engine compartment and gain access to the compressor.
Before sawing the pipes, it is necessary to bleed off the remaining refrigerant. Although there is not much of it in household refrigerators, you should not simply release the gas into the room - it is better to do this through a puncture in the process pipe or carefully cut the pipe in a well-ventilated area. After releasing the pressure, you can begin dismantling.
Disconnect the electrical wires from the contacts of the compressor and the start relay. Remember or take a photo of the connection diagram so that when assembling a new unit you do not confuse the phase, neutral and ground. Then use a pipe cutter to carefully cut the capillary tube and discharge tube. Cut the tubes at a distance of 10-15 cm from the compressor body to leave room for rolling.
⚠️ Attention: Never use a hacksaw to cut tubes! Small metal shavings will inevitably get inside the system, which will lead to clogging of the capillary and rapid failure of the new compressor. Pipe cutter only!
Unscrew the mounting bolts or nuts holding the compressor to the frame. Sometimes they can be rusty, so use a penetrating lubricant. Carefully remove the old unit, trying not to sharply pull the remaining parts of the pipelines, so as not to damage the condenser or evaporator.
Installing and soldering the new compressor
Install the new compressor in its original place and secure it with fasteners. It is important not to overtighten the bolts so as not to strip the threads, but also to ensure rigid fixation, since vibration during operation is unacceptable. Connect the electrical part by installing a new starting relay if the old one is in doubt.
Now the most important step is soldering. Clean the ends of the copper tubes from oxides and dirt. Insert the tubes into the compressor fittings. When soldering, it is important not to overheat the compressor itself, so use a damp rag to cool the motor housing near the soldering area. Heat the joint with a torch evenly, introducing solder into the gap between the tube and the fitting.
A high-quality soldered seam should be smooth, without sagging or pores. Phosphorus-containing solder flows into the gap itself due to capillary effect, so there is no need to pour too much of it. After the seams have cooled, check them visually for cracks.
☑️ Checklist before soldering
If you are changing the type of compressor and the diameters of the tubes do not match, use copper adapters (sleeves). They are put on the tubes and sealed on both sides. This is a standard practice during repairs when an exact analogue of the fittings could not be found.
Evacuation and refrigerant charging
Simply replacing the compressor is not enough - the system must be cleaned of moisture and air. To do this, a vacuum pump is connected to the process pipe (usually a short copper tube coming from the compressor) through a hose. Turn on the pump and leave the system for 15-20 minutes.
Evacuation removes moisture, which at low temperatures turns into ice and clogs the capillary, and also removes air, which increases the pressure in the system. On the pressure gauge you should see a pressure close to -1 bar (or 0 MPa absolute).
After creating a vacuum, close the valve on the manifold and turn off the pump. Now you can start refueling. The refrigerant is charged strictly according to the weight indicated on the refrigerator's factory tag (usually on the inside wall or back). Use electronic scales for accuracy.
| Refrigerant type | Suction pressure (approx.) | Filling features |
|---|---|---|
| R134a | -0.1...-0.15 bar | Refilling in the liquid phase (cylinder upside down) through a filter drier or with the compressor running |
| R600a | -0.05...-0.1 bar | Only liquid phase, strictly by weight, high fire hazard |
| R12 (old) | 0...0.2 bar | Filling with the vapor phase (cylinder up), now rarely used |
Open the gas supply valve and start the compressor. Refrigerant will begin to flow into the system. Monitor the low pressure gauge and the weight of the cylinder. As soon as you have collected the required number of grams, close the valve.
Checking tightness and final startup
After refueling, it is necessary to clamp the process tube and solder it. This must be done carefully so as not to release gas. Use clamping pliers, pinch the tube in two places and cut between the clamps, then quickly solder the tip.
Be sure to check all new solder joints for leaks. To do this, you can use a soap solution: apply it to the seams and turn on the compressor. If bubbles appear, there is a leak that needs to be fixed. There are also electronic leak detectors that respond to freon vapors.
Plug in the refrigerator and leave it running for several hours. Check the temperature in the chambers. The freezer should gain cold evenly. If all parameters are normal, the replacement can be considered successfully completed.
⚠️ Attention: Technical characteristics of compressors and requirements for types of refrigerants may vary depending on the manufacturer and year of manufacture of the model. Always check the technical documentation (datasheet) for a specific motor model before starting work.
Frequently asked questions (FAQ)
Is it possible to replace an R134a compressor with an R600a?
Theoretically it is possible, but this requires a complete flushing of the system, changing the oil and filter drier, as well as resetting the thermostat. It is easier and safer to install the compressor on the same type of refrigerant on which the system originally operated.
Do I need to change the filter drier when replacing the compressor?
Yes, definitely! The filter drier is a disposable element. When the circuit is opened, it absorbs moisture from the air and loses its properties. Installing an old filter is guaranteed to lead to the formation of an ice plug and breakdown of the new compressor.
Why does the new compressor get hotter than the old one?
Modern compressors often have higher efficiency and a smaller oil volume, so their housing can heat up to 70-80 degrees, which is the norm for many models. The main thing is that it does not overheat and does not turn off via a thermal relay.
How much does it cost to replace a compressor yourself?
The cost consists of the price of the compressor itself (from 3,000 to 8,000 rubles), the cost of the refrigerant, filter and consumables. The savings compared to the service are about 50-60%, but require investment in a tool if you don’t have one.