Failure compressor is one of the most serious and expensive breakdowns that the owner of household appliances may encounter. It is this unit that is the “heart” of the system, ensuring the circulation of the refrigerant, and without its correct operation the cooling process becomes impossible. If you hear loud knocking, humming, or, conversely, complete silence when the light is on, most likely it’s time to replace the unit.
Independent installation of a compressor requires not only the presence of special tools, but also a deep understanding of the principles of operation of the refrigeration circuit. This is not just a one-to-one part replacement, as is the case with a shelf or a light bulb; this requires hermetic soldering of pipes, creation of a vacuum in the system and precise dosage freon. Errors at any stage can lead to repeated breakdown of expensive equipment or even to its complete failure.
In this article we will analyze in detail the entire technological process, from diagnostics and selection of spare parts to the final start-up of the unit. You will learn what nuances need to be taken into account when working with copper tubes, why you cannot open the system without protective gas and how to properly carry out pressure testing with nitrogen. It is critically important to understand that working with refrigerants requires compliance with safety precautions, since some gases are under high pressure.
Fault diagnosis and workplace preparation
Before you start dismantling the old equipment, you need to make sure that the problem lies precisely in the motor-compressor. Often, symptoms similar to a breakdown of the “heart” of the refrigerator can be caused by a malfunction of the start relay, thermostat, or electronic control module. The initial check includes a visual inspection for mechanical damage and listening to the operation of the unit at the time of startup.
If the compressor hums but does not start, or starts for a few seconds and clicks when turning off, this is a sure sign of a jammed mechanism or broken windings. It is also worth checking the resistance of the windings with a multimeter: lack of readings or a short circuit will indicate an electrical fault. Once you are convinced of the diagnosis, prepare the workplace: it should be well lit, ventilated and free from flammable objects.
To carry out the work, you will need specialized tools, without which high-quality installation is impossible. The master's standard kit usually includes:
- 🛠️ A torch with a set of solder and flux for soldering copper connections.
- 🔧 Pipe cutter and rolling machine for preparing copper tubes.
- 🌬️ Vacuum pump and pressure gauge station to create a vacuum and charge.
- ⚖️ Electronic scales for accurate weighing of refrigerant.
⚠️ Attention: It is strictly forbidden to carry out soldering in a confined space without ventilation, since flux vapors and possible gas leaks can be toxic. Also make sure that there are no open flame sources nearby other than your burner.
Removing the old compressor and preparing the system
The dismantling process begins with completely disconnecting the refrigerator from the power supply. This is a basic electrical safety rule, which, if ignored, can result in electric shock. After disconnecting, you must gain access to the lower rear part of the unit, where the compressor compartment is located. Remove the protective cover and casing covering the motor.
The next step is to remove the old refrigerant from the system. If there is residual pressure in the tubes, it must be released through a puncture in the process pipe. This must be done carefully, using a punch or cutting the tube with wire cutters, having previously placed a container for oil, which may come out along with the gas. Freon lighter or heavier than air, depending on the type, so it is important to ensure good traction.
After releasing the pressure and disconnecting the electrical wires (previously take a photo of the connection diagram!) You can start unsoldering the tubes. Heat the junction of the suction and discharge pipes with a torch to the melting temperature of the solder. When the solder becomes liquid, carefully separate the tubes. Be careful not to damage the copper capillaries leading to the evaporator.
What to do with the remaining oil in the system?
If the old compressor burned out with a bang, an acid deposit could remain in the system. In such cases, it is recommended to flush the circuit with nitrogen under pressure or replace the filter drier and capillary tube, since acid can quickly damage the new motor.
The disconnected compressor is removed from the mounting pins or shock absorbers. They often rust and may require the use of a penetrating lubricant. After removing the old unit, inspect the condenser grille for mechanical damage or corrosion that could have occurred during long-term operation.
Selecting and preparing a new compressor
Choosing a replacement compressor is not just buying the first part you come across with a similar volume. It is necessary to strictly observe the parameters indicated on the nameplate of the old device or in the technical documentation of the refrigerator. The key parameters are the cooling capacity (in W or kcal/h), the type of refrigerant (R134a, R600a) and overall dimensions so that the new motor fits into place.
The new compressor is supplied sealed and filled with nitrogen under low pressure. This is done to prevent oxidation of internal parts during storage. You can open the factory plug on the pipes only immediately before soldering. If you open the system in advance, moisture from the air will get inside, which is unacceptable for the refrigeration circuit.
Before installation, it is recommended to check the condition of the start relay and capacitor. Even if they are working properly, installing new components along with the compressor significantly reduces the risk of re-use. Also, be sure to replace filter drier, since the old one could already be saturated with moisture and will not be able to work effectively in the new system.
Synthetic (POE) or mineral (Mineral)
| Parameter | Description | Importance |
|---|---|---|
| Refrigerant type | Must strictly comply with the marking (R134a or R600a) | Critical |
| Cooling capacity | Cooling power, selected according to the correspondence table | High |
| Dimensions | Distance between paws and height of pipes | Average |
| Oil type | Critical |
Technology for soldering copper connections
The quality of soldering determines the tightness of the entire system. Brazing solder (usually containing 5-15% silver) and flux are used to join copper tubes. Before soldering, the ends of the tubes must be cleaned to a shine, removing oxides and contaminants. If the new compressor has steel pipes, the connection technology will be different and will require the use of special adapters or soft solder.
The soldering process is as follows: flux is applied to a tube heated by a torch, then a solder rod is introduced into the flame. The solder should melt from the heat of the tube, and not from the open flame of the burner, flowing into the gap due to capillary effect. It is important to heat the connection evenly on all sides to avoid “cold soldering,” which can crack due to vibration.
When installing a compressor with your own hands, the question often arises: in what order should the tubes be soldered? It is recommended to first solder the discharge line (output to the condenser), then the suction line (from the evaporator) and lastly the process pipe for filling. During soldering, it is better to keep the process pipe open or with a minimal hole so that excess pressure is not created inside.
- 🔥 The burner flame should be directed at the joint of the pipes, and not at the solder itself.
- 💧 Avoid overheating, which can lead to the formation of carbon deposits inside the tube.
- 🧹 After cooling, be sure to remove any remaining flux with a damp rag, as it is aggressive to copper.
⚠️ Attention: When soldering near the plastic elements of the refrigerator, use a wet cloth or metal screen so that the heat does not deform the case or insulation.
☑️ Check before vacuuming
Evacuation and pressure testing of the system
After soldering is completed, air and moisture vapor remain in the system, which are strictly unacceptable. The air creates an “air lock” that increases the condensation pressure, and moisture at low temperatures turns into ice, clogging the capillary tube. Therefore, the evacuation stage is mandatory and cannot be ignored.
A vacuum pump connected to a pressure gauge station is used to remove air. The pump is turned on and the system is evacuated until a deep vacuum is reached (usually around -1 Bar or lower, depending on the type of oil). Evacuation time should be at least 30 minutes for small systems and up to an hour for two-compressor models. This ensures the evaporation of all moisture from hard-to-reach places.
After pumping, it is necessary to carry out pressure testing with nitrogen to check the system for leaks. Nitrogen is supplied under pressure of 10-15 atmospheres (for domestic refrigerators). The pressure gauge is left under observation for several hours: if the needle does not fall, then the system is sealed. The use of pure nitrogen is important because it is inert and does not react with oil and freon.
Some craftsmen neglect nitrogen pressure testing, relying only on vacuum. However, a vacuum may not show a microcrack that will open under operating pressure. Nitrogen pressure testing is the only reliable way to guarantee the absence of leaks before charging with expensive refrigerant.
Refrigerant charging and first start-up
The final stage is filling the system with refrigerant. The amount of freon is strictly regulated by the manufacturer and is indicated on a sticker inside the refrigerator compartment or on the compressor. A deviation of even 10-15 grams can lead to incorrect operation: underfilling will cause overheating of the compressor, and overfilling will cause liquid shock and lack of cold.
Refilling is done through the process pipe using scales to control the mass. The freon cylinder is placed on the scale, the initial value is recorded and the valve is opened, supplying gas to the system. For accuracy, it is better to fill in the liquid phase (turning the cylinder over), but very slowly, so that the compressor does not experience a hydraulic shock if it is already running, or fill the system when it is turned off.
After filling, the process pipe is clamped with a clamp, sealed and cut off. Then a test run is carried out. During the first minutes of operation, carefully monitor the suction and discharge pressures, as well as the temperature of the compressor housing. It should be hot, but not scalding.
Check the operation of the refrigerator for several hours. The freezer should reach temperature, and the shelves of the main compartment should become cold. If all parameters are normal, the installation can be considered complete.
Common mistakes when replacing yourself
One of the most common mistakes is ignoring the replacement of the filter-drier. The old filter may be saturated with moisture, which will quickly transfer into the new compressor, causing corrosion of the windings and destruction of the oil. Saving on this small part often leads to expensive repairs after a few months.
Another mistake is insufficient vacuuming time. Owners often think that 5-10 minutes of pumping is enough, but moisture remains in deep layers of oil and in bends of pipes. As a result, after a week of operation, the refrigerator stops freezing due to an ice plug in the capillary.
Incorrect selection of a compressor analogue is also common. Installing a more powerful motor “by eye” will lead to the fact that the evaporator will not have time to give off cold, and the condenser will not have time to dissipate heat. This causes constant wear and tear of the unit and high energy consumption.
Is it possible to use a compressor from another refrigerator model?
You can use a compressor from another model, but only if the basic technical characteristics match: cooling capacity, type of refrigerant and type of oil. The overall dimensions and location of the pipes must also match, otherwise the pipelines will have to be redone, which is not always possible at home.
How long does it take to replace a compressor?
For an experienced technician with ready-made equipment, the process takes from 1.5 to 3 hours, including time for vacuuming and crimping. At home, without experience, you can spend up to 5-6 hours for the first time, since it takes time to carefully solder and wait for the results of a leak test.
Why, after replacing the compressor, does the refrigerator freeze but does not turn off?
This may indicate several problems: a freon leak (undercharging), a blockage in the capillary system, or a malfunction thermostat. Also, the reason may be a leak in the door seal, due to which heat constantly enters the chamber, and the automation does not give the command to stop.
Is it necessary to flush the system if the old compressor has burned out?
Yes, if the compressor has burned out with the release of acid and fumes, flush the system with a special solvent or nitrogen under pressure required. If this is not done, acid residues will circulate through the system and destroy the new motor in a short time.
Which gas is safer for self-refueling?
From a safety (explosion hazard) point of view, R134a is safer than R600a. Isobutane (R600a) is a light gas and forms an explosive mixture at concentrations in air greater than 1.3%. Therefore, when working with R600a, special care and no sparks are required.