Failure of the motor-compressor is perhaps the most serious and expensive malfunction that the owner of household appliances may encounter. When the refrigerator stops cooling, but there is silence inside or, conversely, a humming sound is heard, but there is no cooling, most often it is the culprit. Many people call a professional right away, but for those who have basic tool skills and understand how refrigeration systems work, doing the replacement yourself can be a way to save a significant amount of money. However, it is important to realize: this process requires not only mechanical dexterity, but also the presence of specific equipment. compressor. Many people call a professional right away, but for those who have basic tool skills and understand how refrigeration systems work, doing the replacement yourself can be a way to save a significant amount of money. However, it is important to realize: this process requires not only mechanical dexterity, but also the presence of specific equipment.
Before proceeding with dismantling the old unit, it is necessary to conduct a thorough diagnosis to make sure that the problem lies in the heart of the refrigerator, and not in the start relay or thermostat. Replacing the compressor —this is not just unscrewing bolts, it is working with a sealed system, requiring complete evacuation of the refrigerant, high-quality soldering of copper tubes and subsequent evacuation of the circuit. Ignoring any of these stages will lead to the fact that the new motor will burn out in a matter of days or weeks, and the money will be wasted.
In this article we will analyze in detail the entire technological process, from the selection of components to the test launch of the updated unit. You will learn about the nuances of working with different types of refrigerants, such as R134a or R600aand understand why system cleanliness is a critical success factor. We will also discuss safety precautions, as working with high pressure and flammable gases requires special care and compliance.
Diagnostics and selection of a new compressor
The first step should always be to accurately identify the problem. If the refrigerator turns on, hums for a couple of seconds and turns off, or runs constantly but does not freeze, these are classic signs of a compressor malfunction. However, before purchasing a new spare part, you need to make sure that the capillary is not clogged and that the defrost system is working properly. Check the starting relay: if it is stuck or burnt out, the motor itself may be fine. To check the resistance of the windings, use a multimeter, measuring the indicators between the contacts starting, the working winding and the housing.
When choosing a new unit, the key parameter is its power and type of refrigerant. You can't just buy any motor of a similar size. You need to find the factory sticker on the old compressor (if it is readable) or the refrigerator passport. Pay attention to the labeling: the letters at the end often indicate the type of freon. For example, R600a (isobutane) requires special explosion-proof components and oils that are incompatible with systems on R134a.
It is also important to consider the performance in cubic centimeters (cm³) or watts (W). Installing a more powerful compressor will lead to incomplete evaporation of freon and the liquid fraction entering the motor, which will cause water hammer. A less powerful unit simply will not be able to provide the necessary cooling capacity, and the refrigerator will work without stopping.
⚠️ Attention: Never mix oils and refrigerants of different types! Mineral oil (for R12/R600a) and synthetic oil (for R134a) when mixed form an acidic environment, which in a few months will destroy the insulation of the windings and render the new compressor inoperable.
Required tools and materials
High-quality repairs are impossible without the appropriate tools. Unlike replacing filters or light bulbs, working on a refrigeration circuit requires a professional approach. The basic set includes a gas burner (propane-oxygen or propane-air), a pipe cutter, a flange and a set of keys. Particular attention should be paid to tools for working with copper, since the tightness of the entire system depends on the quality of the seam.
To fill the system and remove moisture, you will need a vacuum pump and a pressure gauge station (manifold). Without evacuation, moisture and air will remain in the system, which will turn into an ice plug in the capillary or cause oxidation of the oil. You also need scales for accurate charging with freon, since the amount of refrigerant is calculated to the gram.
Below is a table of the main tools and their purposes for successful work:
| Tool | Purpose | Criticality |
|---|---|---|
| Gas burner | Soldering copper tubes with solder | High |
| Vacuum pump | Removing air and moisture from the circuit | Critical |
| Gauge station | Pressure control during evacuation and filling | High |
| Pipe cutter | Even cut of copper tubes without deformation | Medium |
| Electronic scales | Accurate refrigerant dosage | High |
Preparation for dismantling and safety precautions
Before starting any work, the refrigerator must be completely defrosted and disconnected from the power supply. Even if it seems that there is no ice inside, moisture may be hiding in hard-to-reach places of the evaporator. Safety - above all: make sure that the room has good ventilation, especially if you are working with flammable R600a. A spark from a soldering iron or static electricity can cause a gas fire.
Remove the rear access panel to the compressor compartment. Move the refrigerator away from the wall to allow easy access on all sides. Prepare a container to catch any old oil that may leak out when cutting the pipes. Check in advance that the new compressor has transport plugs on the nozzles - they need to be opened immediately before soldering to minimize oil contact with air.
It is also important to prepare the workplace. Remove flammable objects, carpets and curtains from the burner area. Have a fire extinguisher on hand. If you are working with R600a, exclude any sources of open flame, except the burner itself, and do not smoke indoors.
☑️ Preparation for replacement
Process of dismantling the old compressor
The removal process begins with carefully cutting through the filling and process tubes. This should be done with a sharp movement of the pipe cutter or side cutters so as not to flatten the copper. At this moment, the remaining freon and oil will come out of the system under pressure. Be prepared for the fact that the oil may have a pungent odor and a specific color - this is a normal oxidation reaction.
After releasing the pressure, you can begin to solder the tubes. Heat the soldering area evenly with a torch. Once the solder has melted, carefully pull the tube using pliers. The main thing here is not to overheat the compressor or condenser itself, since high temperatures can damage the varnish coating of the windings or plastic elements nearby. Use a wet rag to cool adjacent components if necessary.
Unscrew the mounting bolts or nuts holding the compressor to the frame. They are often rusty, so treat them with a penetrating lubricant (WD-40 or equivalent) beforehand. Remove the old unit. Pay attention to the condition of the rubber shock absorbers - if they become stiff or cracked, they must be replaced, otherwise the vibration of the new motor will be transmitted to the refrigerator body.
⚠️ Attention: It is strictly forbidden to open the process pipes of the new compressor until you are ready to immediately start soldering. An open compressor begins to actively absorb moisture from the air, which will lead to the formation of acid in the oil and rapid failure of the unit.
Installing and soldering a new unit
Installation of a new compressor is carried out in the reverse order of dismantling. Secure the motor to the frame using new fasteners if the old ones have become unusable. Connect the suction and discharge pipes. It is important to observe the geometry here: the tubes should not touch each other or the body in order to avoid rattling and chafing during vibration.
Soldering is the most critical stage. Use flux to solder copper, but apply only a minimal amount. Excess flux inside the tube can clog the capillary. Heat the joint with a torch until the solder begins to melt and flow into the gap by capillary action. The seam should be smooth, without cavities or sagging. Pay special attention to the filter-drier: it must be changed whenever the system is depressurized.
The filter-drier is installed vertically, the arrow on the body should indicate the direction of freon flow (from the condenser to the capillary). You need to solder the filter very quickly and carefully so as not to overheat its body, otherwise the adsorbent inside will lose its properties and turn into dust, clogging the system.
Why can’t you solder the filter for a long time?
The filter drier contains zeolite or silica gel, which, when heated strongly above 150°C, release bound moisture back into the system. This will negate all vacuuming efforts. Therefore, when soldering, the filter housing is wrapped in a wet rag or a heat-dissipating clamp is used.
Evacuating and filling with refrigerant
After checking the tightness of the seams (you can blow the system with nitrogen under a pressure of 10-15 bar and check with a soap solution), the vacuuming stage begins. Connect the vacuum pump to the process connection. The operating time of the pump depends on its performance and the volume of the system, but usually ranges from 30 to 60 minutes. The goal is to achieve a deep vacuum in order to boil away all moisture from the oil and from the walls of the tubes.
After evacuation, close the valve on the manifold and turn off the pump. Wait 15-20 minutes and look at the pressure gauge: the needle should not deviate from zero. If the pressure rises, then there is a leak in the system that needs to be found and eliminated. Only after making sure of the tightness, you can start refueling.
Refill strictly according to the weight indicated on the factory sticker of the refrigerator. The freon cylinder is placed on the scale, the valve opens, and the refrigerant enters the system. For R134a refueling is done in the liquid phase (an upside-down cylinder is not needed if the liquid phase is used through a scale, but it is often poured in the gas phase while the compressor is running, controlling the current). For R600a refilling is always done in the gas phase (cylinder upside down), since it is a flammable gas, and pouring liquid into a running compressor is dangerous.
Frequent errors and troubleshooting
Even experienced craftsmen can make mistakes that lead to repeated repairs. One of the most common is insufficient vacuum time. The moisture remaining in the system freezes in the capillary tube, blocking the circulation of freon. Outwardly, it looks like a working compressor, but without cold. There is only one solution: redo the work again.
Another mistake is overheating of the compressor during soldering. If you heat the suction tube for a long time, the heat may transfer to the motor housing and damage the internal electrical insulation. Also, a common problem is installing a filter-drier “by eye” without taking into account the direction of flow, which makes it useless.
If after starting the refrigerator freezes, but after a couple of hours it stops, most likely an ice plug has formed. If the compressor hums but does not start, it may be jammed due to water hammer (liquid freon ingress) or a faulty start relay. In the case of R600a always check the system for leaks with a gas analyzer, since the gas is odorless and colorless.
Is it possible to replace a compressor without a vacuum pump?
Theoretically, some “Kulibins” use the method of squeezing out air with the refrigerant itself (purge), but this is highly not recommended. Without a vacuum, moisture remains in the system, which will quickly kill the new compressor and clog the capillary with ice. The service life of such a repair will be from several weeks to a couple of months.
Why does a new compressor get hotter than the old one?
Modern compressors often have a higher energy efficiency class and operate at higher condensing temperatures. However, if the motor housing itself heats up (exorbitantly, to the point of being impossible to touch), this may indicate improper refueling (underfilling or overfilling), the presence of air in the system, or problems with ventilation around the motor.
Is it necessary to flush the system when replacing a compressor?
Flushing the system with nitrogen or a special solvent is mandatory, if the old compressor burned out and released combustion products and acid into the system. If the compressor simply stops pumping or jams without combustion, it is enough to replace the filter drier and thoroughly purge the system with dry nitrogen.
Which solder is best to use for copper?
For soldering copper tubes of refrigerators, silver solder (with a silver content of 15-45%) is best suited. It has excellent fluidity, strength and a melting point close to copper. The use of brass solders with a high zinc content is undesirable, since the zinc burns out and makes the weld brittle.