The situation when the refrigerator stops cooling, and diagnostics indicate a motor malfunction, often confronts the home craftsman with a choice: buy an expensive new unit or try to revive old. Replacement compressor is a difficult but doable task for a person with a technical mind and a basic set of tools. The process requires not only physical actions for dismantling and installation, but also a deep understanding of the principles of operation of the refrigeration circuit.
Before proceeding with disassembly, you need to make sure that all components are available, since sealed unit it is often sold without a start-up relay and capacitor. An incorrect connection can lead to instant failure of the new node or even a short circuit in the network. In this article we will analyze in detail all the stages, from preparation to the first start-up, in order to minimize risks.
It is worth noting right away that working with refrigerants and high-voltage electrical circuits requires increased caution. If you are not confident in your abilities or you do not have experience working with soldering station a vacuum pump, it is better to entrust this task to professionals. However, for those who decide to act independently, knowledge of the theory will become the foundation for successful repairs.
Preparatory stage and necessary tools
The success of any technical operation depends 80% on the quality of preparation. You will need not only a new compressor, but also a specialized tool that is rarely found in a standard home repair kit. Without vacuum pump a pressure gauge station, it is almost impossible to do the job efficiently, since the system must be absolutely dry and free of air.
Be sure to check the technical characteristics of the unit being replaced. Power, type of refrigerant (for example, R134a or R600a) and overall dimensions must completely match the original. Using an unsuitable motor will lead to incorrect operation of the thermostat and rapid wear of parts.
For work you will need:
- 🔧 A set of wrenches and screwdrivers of various sizes.
- 🔥 Torch with solder (for soldering copper tubes).
- ⚡ Multimeter for checking the integrity of the windings.
- 💨 Vacuum pump and filling hose.
- 🧤 Protective gloves and glasses.
⚠️ Attention: Before starting any work, be sure to disconnect the refrigerator from the power supply! Working with live electrical components is deadly.
It is also worth preparing the workplace. It should be well lit and ventilated, especially if soldering and working with gases are planned. Make sure you have a fire extinguisher in advance in case the materials catch fire.
☑️ Prepare to replace the compressor
Removing the old compressor and preparing the system
The first step is to remove the old unit from the housing. To do this, you need to remove the rear protective panel of the refrigerator and gain access to the bottom part, where motor-compressoris located. Carefully disconnect all electrical wires, having previously photographed the connection diagram so that when installing a new unit you do not get confused in the contacts.
The next stage is the desoldering of the copper tubes. The important thing here is not to damage other elements of the system, such as the condenser or filter drier, if you plan to leave them. Heat evenly using flux and solder designed for copper. After disconnecting the tubes, the old compressor can be removed from the frame.
If you plan to use the old compressor for other needs (for example, as an air blower for painting), then before connecting it to a 220V network, you need to drain the mineral oil from it and replace it with regular motor oil. The refrigeration circuit uses a special synthetic oil, which is not suitable for pneumatic tools and can foam.
It is important to thoroughly clean the areas of future soldering from oxides and contaminants. Use fine sandpaper or a special brush. The quality of the tube connection directly affects the tightness of the entire system. Even a microscopic crack will lead to a freon leak after several months of operation.
What to do with used oil?
Old oil from the compressor contains acidic impurities and wear products. It should not be poured down the drain or onto the ground. Collect the liquid in a sealed container and take it to a hazardous waste collection point.
Electrical connection diagram
The electrical connection diagram of the compressor is a critically important component, an error in which can cost the life of the unit. Unlike simple electric motors, a special combination is used here: starting relay and a thermal protection relay. They ensure the correct start of the rotor and turn off the motor when overloaded.
The standard circuit assumes the presence of three contacts on the compressor block. They are usually marked with letters or arranged in a specific geometry (triangle). The main pins are "Common", "Run" and "Start". By mixing them up, you risk burning the stator winding in a matter of seconds.
Consider a typical sequence of actions when connecting:
- 🔌 Determine the contacts on the compressor block using a multimeter in dial mode.
- ⚙️ Set the starting relay strictly in vertical position (usually the "UP" arrow should point upward).
- 🔗 Connect the capacitor (if provided by the design) in parallel with the starting winding.
- 🛡️ Cover the contacts with a protective casing of the relay.
In modern inverter models, the circuit is much more complicated and includes an electronic unit speed control. It is impossible to connect such a compressor directly to a 220V network “bypassing” the electronics using standard methods - it simply will not start or will fail.
⚠️ Attention: The starting relay must correspond to the power of the specific compressor. Using a relay from a different model may cause the contacts to stick and the motor to burn out.
To check the correct connection, you can briefly apply voltage. If a confident hum is heard, and after a few seconds the relay clicks off (when the shaft is blocked or there is no pressure), then the circuit is assembled correctly. However, it is better to carry out a full check on the already assembled system.
Soldering copper tubes and installing a filter-drier
The mechanical connection of the compressor to the refrigerator circuit is carried out by soldering copper tubes. This requires skill in working with open flames. The tube is put on the compressor fitting with a gap of 1-2 mm, after which it is heated to cherry color and sealed with solder.
The critical point is replacement filter-drier. This element is responsible for removing moisture and acidic residues from the system. When the circuit is opened, the filter becomes saturated with moisture from the air and loses its properties. Installation of a new filter is mandatory in case of any depressurization of the system.
When soldering, follow the following rules:
- 🔥 Heat the tube evenly around the circumference, and not at one point.
- 💧 Do not allow solder to get inside the tube so as not to create a blockage.
- 🌬️ Purge the tubes with nitrogen during soldering to prevent the formation of an oxide film inside.
The filter drier is also soldered to the system. Pay attention to the refrigerant flow direction arrow stamped on the filter housing. Incorrect installation will lead to disruption of freon circulation and lack of cold.
After soldering all connections, it is necessary to allow the system to cool naturally. Do not cool soldering areas with water or compressed air, as sudden temperature changes can cause microcracks in the seam.
Evacuation and refrigerant charging
Assembly of the mechanical part is completed, but there is still air and moisture in the system. The air contains water vapor, which, when frozen in the capillary tube, forms an ice plug that blocks the operation of the refrigerator. Therefore, the stage evacuation is mandatory.
A pressure manifold and a vacuum pump are connected to the service pipe of the compressor. The pump turns on for 15-30 minutes. During this time, the pressure in the system should drop to a deep vacuum (about -1 Bar or lower). This allows you to evaporate and remove all moisture.
Table of typical parameters for different refrigerants:
| Refrigerant type | Evaporation pressure (at -25°C) | Oil type | Features |
|---|---|---|---|
| R134a | 1.0 - 1.2 bar | Synthetic (POE) | Hygroscopic, requires careful drying |
| R600a | 0.4 - 0.6 bar | Mineral | Explosive, small filling |
| R12 (old) | 1.2 - 1.4 bar | Mineral | Prohibited for production, ozone-depleting |
| R404A | 1.5 - 1.8 bar | Synthetic | High pressure, for low temperatures |
After evacuation, the valve on the pump is closed and the system is checked for seal for 10-15 minutes. If the pressure gauge needle does not deviate, you can start refueling. The refrigerant is charged strictly according to the weight indicated on the refrigerator nameplate, accurate to the nearest gram.
Refilling is carried out with the compressor running (if the valve design allows it) or off under pressure, after which a test run is performed. Excess or lack of freon is equally harmful to the system.
⚠️ Attention: Refrigerant R600a (isobutane) is explosive when concentrated in air. All work with it should be carried out in a well-ventilated area away from spark sources.
Startup and initial diagnostics
The final stage is the first launch of the repaired refrigerator. Plug in the unit and listen to the motor. The launch should be soft, without strong jerking or buzzing. After 5-10 minutes of operation, check the temperature of the compressor housing - it should heat up evenly.
Be sure to check the operation of the thermostat. The refrigerator should turn off when the set temperature is reached and turn on when it rises. If the motor runs continuously for more than an hour and does not turn off, and the cold does not accumulate, there may be a leak or blockage of the capillary.
What to look for when diagnosing:
- 👂 Absence of extraneous knocks and metallic clanging.
- 🌡️ Uniform cooling of the condenser (grids at the back).
- ❄️ The appearance of frost on the evaporator inside the chamber.
- 📉 Correct shutdown by timer or thermostat.
If all parameters are normal, you can seal the service pipe and install the back cover. However, during the first 24 hours, it is recommended to periodically check the temperature in the chambers to ensure stable operation.
Is it possible to connect a compressor from a refrigerator without a relay?
Technically, you can start the engine by applying voltage directly to the working and starting windings for a short time, but you cannot operate the refrigerator in this mode. Without a protection relay, the motor will burn out at the first overload or power surge. The relay is a mandatory safety element.
Why does the compressor hum but does not start?
Most often this indicates a malfunction of the starting relay (contacts stuck or the coil burnt out) or a jammed piston group of the compressor itself (“wedge”). In some cases, “wedging” by applying increased voltage helps, but this is a temporary measure.
What kind of oil should be poured into the compressor when replacing?
The type of oil depends on the type of refrigerant. For R134a and R404 freons, synthetic polyester oil (POE) is required, since it is mixed with freon. For R12 and R600a, mineral oil is used. They must not be mixed!
Does the system need to be flushed when replacing a compressor?
If the old compressor burns out with the release of black soot into the system, flushing the circuit with nitrogen or a special solvent is mandatory. Otherwise, combustion products will quickly clog the capillary tube and the new filter-drier.