Restoring the functionality of household appliances is not just saving the family budget, but also a way to extend the life of reliable units that have served for decades. Often owners are faced with a situation where refrigeration circuit it is working properly, and the cause of the breakdown lies precisely in the failure of the electric motor. Replacing this unit requires accuracy, understanding of the principles of operation of electrical circuits and compliance with strict safety rules when working with refrigerants and high voltage.
The process of replacing motor-compressor with an old refrigerator differs significantly from installation in new equipment, since it requires the selection of an analogue in terms of power and dimensions, as well as the correct soldering copper pipes. An incorrect connection can lead to instantaneous burnout of the windings or, even worse, to depressurization of the system and leakage of freon. In this article we will analyze in detail all stages of work, from diagnostics to the first start.
Before taking up the tools, you need to realize that working with refrigeration units is fraught with risks. Electric current in a 220-volt network is dangerous to life, and refrigerants under pressure require careful handling. If you are not confident in your abilities or do not have experience working with a blowtorch and multimeter, it is better to turn to professionals. However, if the decision is made, be patient and have the necessary components for a successful repair.
Fault diagnosis and selection of a new compressor
The first step should always be a thorough diagnosis to make sure that the problem is really in the compressor and not in the thermostat or start relay. It often happens that it is motor functional, but cannot start due to oxidized contacts or a malfunction of the temperature sensor. Check whether voltage is supplied to the terminals, and test the windings with a multimeter for an open or short circuit.
If the diagnosis is confirmed, it is necessary to select a replacement. For older models of refrigerators, such as ZIL, Biryusa or Soviet Don, finding an original compressor may be difficult, but possible. It is important to pay attention not only to the dimensions and fastening of the paws, but also to the power, type of refrigerant (R12 or R134a) and the volume of pumped oil.
⚠️ Attention: Never install a compressor designed for one type of freon in a system charged with another without completely flushing the circuit and changing the oil. This will lead to a chemical reaction, the formation of acid and rapid failure of the entire system.
When purchasing a used unit, be sure to check its performance before installation. Connect it to the network through a working start relay and make sure that it creates sufficient pressure at the outlet and vacuum at the inlet. Also inspect the body for signs of corrosion, dents or oil smudges, which may indicate hidden defects.
Necessary tools and materials for work
High-quality repairs are impossible without suitable tools. To dismantle the old one and install the new one unit you will need a set of wrenches, screwdrivers, pliers and wire cutters. Particular attention should be paid to tools for working with copper tubes: a pipe cutter, rolling (if you plan to roll joints) and, of course, a torch for soldering.
Soldering copper tubes requires the use of solder with a melting point above 600 degrees (hard solder) and flux. For older systems, copper-phosphorus solder is often used, which does not require additional fluxes for copper, but for joining copper to steel (compressor pipes), flux and silver solder are required. You will also need a nitrogen cylinder for purging the system if you plan to do this using technology.
- 🔧 A set of wrenches and screwdrivers for dismantling fasteners.
- 🔥 Gas burner with a cylinder (propane-butane or oxygen-acetylene).
- 🧪 Solder (silver or copper-phosphorus) and flux for soldering.
- 📏 Pipe cutter and reamer for preparing the edges of copper tubes.
- ⚡ Multimeter for checking electrical parameters and circuit integrity.
Don't forget to prepare a container for collecting old oil and rags for cleaning surfaces. The workplace must be well ventilated, since when soldering and burning old varnish, harmful substances can be released on the windings. Make sure in advance that you have access to a source of open fire and electricity.
Preparation for replacement: safety and dismantling
You can start work only after completely disconnecting the refrigerator from the power supply. Unplug the cord from the outlet and move the unit to a free space, ensuring access from all sides. Old refrigerators often have heavy metal grilles on the back that must be carefully removed by unscrewing the mounting screws.
The next step is to remove the old compressor. To do this, you need to bite the copper tubes going to the discharge and suction pipes, as well as to the process tube (for refilling). Important: before biting off the pipes, make sure that there is no pressure in the system, otherwise residual oil and freon may splash. Then unscrew the compressor from the refrigerator frame.
When dismantling the electrical part, be careful with the wires. Take a photo of the connection diagram or sketch it so as not to confuse the colors when installing a new device. Typically the wires run from the thermostat and safety relay to the compressor start relay. Carefully remove the casing from the terminal box of the old motor and disconnect the terminals.
☑️ Preparing to replace the compressor
After removing the old unit, clean the installation site from dirt, dust and old oil. If there are rubber shock absorbers left on the frame, check their condition: if they are cracked or fossilized, it is better to replace them so that the new compressor does not vibrate excessively. Also inspect the condenser (black coil at the back) for severe corrosion or damage.
Connection diagram and electrical installation
The electrical connection diagram for the compressor is relatively simple, but requires care. The main elements of the circuit: thermostat, start relay, thermal protection relay and the electric motor itself. In older models, the starting relay is often made in the form of a separate “pill” or box that is placed over the compressor contacts.
To connect, you need to connect the wires according to the color coding, which is usually indicated on the diagram inside the casing or on the relay body. Standard colors: white or red wire goes to the starting winding (via the relay), black or brown - to the working winding, yellow-green - grounding (case). If the colors of the wires of the new compressor differ from the old ones, be guided by the diagram of a specific device.
| Contact on the relay | Purpose | Wire color (standard) | Where it goes |
|---|---|---|---|
| L (Line) | Phase (input) | Brown / White | From the thermostat |
| S (Start) | Start winding | Black / Red | Start relay |
| R (Run) | Working winding | Blue / Green | Main circuit |
| PE | Grounding | Yellow-green | Case refrigerator |
After connecting the wires, securely fasten the starting relay to the compressor contacts. It should fit snugly, without play, and match the “UP” marking or arrow pointing up. Incorrect orientation of the relay will result in the compressor not starting or humming but not turning.
What to do if the wires are mixed up?
If the starting and operating windings are mixed up, the compressor may hum, overheat and quickly burn out, since the starting winding is not designed for long-term use work under load. Always check the circuit before turning it on.
Soldering copper tubes and sealing the system
The mechanical installation is completed, now the most important stage awaits - soldering the copper tubes. There are plugs on the pipes of the new compressor and in the refrigerator system. Remove them immediately before soldering to prevent air and moisture from entering the tubes. If the new compressor came with oil, make sure that the shipping plugs were in place.
The soldering process requires heating the tube until cherry red. Apply solder to the joint area: it should melt from the heat of the metal, and not from the burner flame, and flow into the gap under the influence of capillary effect. For copper-steel connections (compressor pipes), use silver solder and flux; for copper-copper connections, use copper-phosphorus solder without flux.
- 🔥 Heat the tube evenly, moving the flame around the connection.
- 💧 Do not overheat the soldering area so as not to burn it copper and not create burnout.
- 🧊 Let the connection cool naturally, do not blow on it or pour water.
After soldering all connections (discharge, suction, process tube), it is necessary to check the system for leaks. To do this, apply nitrogen under a pressure of about 10-12 atmospheres through the process tube and generously lubricate all seams with soap solution. The appearance of bubbles will indicate a soldering defect that needs to be eliminated.
⚠️ Attention: It is strictly forbidden to use an open flame near gas-filled systems to check the tightness. Use only nitrogen or dry air if the system is evacuated and not yet charged with freon.
Evacuation and first start-up of the system
Before charging with refrigerant, it is necessary to remove air and moisture from the system using a vacuum pump. Connect the pump to the process tube and turn it on. Evacuation should last at least 30-40 minutes for old systems to ensure that moisture is removed, which at low temperatures will turn into ice and clog the capillary.
After creating a vacuum, close the pump valve, turn it off and let the system stand for 15-20 minutes. If the pressure gauge needle does not move from zero, then the system is sealed. Now you can refill with freon. For old refrigerators, freon R12 or its modern analogues are usually used, but look at the nameplate of the refrigerator for the exact brand.
Start the compressor and let it run for a few minutes, then close the filling valve and solder the process tube. Plug in the refrigerator and set the thermostat to the middle position. After 15-20 minutes, check the heating of the condenser (it should be warm) and the operation of the evaporator (it should start to get colder).
Frequent errors and troubleshooting
Even experienced technicians sometimes make mistakes that can cost a new compressor. One of the most common is insufficient evacuation time, which leads to freezing of moisture in the capillary tube. Another mistake is overheating of the compressor during soldering, when heat is transferred to the motor housing, damaging the internal insulation of the windings.
If after connection the compressor hums but does not start, check the voltage in the network and the serviceability of the starting relay. The relay may be stuck or does not match the engine model. Also, the cause may be a wedge in the mechanical part of the compressor, which happens during prolonged downtime or operation without oil.
Why does the compressor get very hot after replacement?
Strong heating can be caused by several factors: excessive freon charging, air entering the system, a malfunction of the condenser (poor ventilation) or a wedge of the piston group. Also, the reason may be a discrepancy between the power of the new compressor and the volume of the refrigeration chamber.
Is it possible to use a compressor from another brand?
Yes, you can, if the overall dimensions, power, type of refrigerant and diameter of the pipes match. However, it is better to select an analogue that is recommended by the manufacturer or has similar technical characteristics (cooling capacity).
Is it necessary to change the filter drier?
When replacing a compressor or a leak in the system, replacing the filter drier is mandatory. The old filter is already saturated with moisture and will not be able to protect the system from the formation of acid and ice plugs.
What to do if there is still a leak after soldering?
It is necessary to completely relieve the pressure, clean the leak site again, apply flux and heat the connection to the melting temperature of the solder, adding a little new material. After cooling, the procedure for checking with a soap solution must be repeated.