A sudden cessation of refrigeration in one of the chambers of the refrigeration unit is always stressful, because people are under threat food supplies. Most often, the cause of such a failure is a failure evaporator, which is directly responsible for the extraction of heat from the internal space of the chamber. If you notice that the compressor is running without interruption, and the temperature does not drop below +10...+15 degrees, or a “coat” of ice has formed on the walls, which cannot be removed by normal defrosting, then most likely there has been a refrigerant leak or mechanical damage to the tubes.
Independent replacement of this unit requires not only technical skills, but also an understanding of the principles of operation of the refrigeration system. The process includes not just the mechanical installation of a new part, but also complex operations of evacuating the system and filling with freon. Important understandthat without specialized equipment (vacuum pump, pressure gauge station) and skills in working with a soldering torch, it is almost impossible to perform high-quality repairs, however, knowledge of the theory will help you make the right decision about the advisability of contacting the service.
In this article we will analyze in detail the stages of diagnostics, selection of components and the replacement technology itself so that you can assess your strengths and risks. Even if you decide not to take on the tool yourself, information about the cost of the work and the complexity of the process will help you avoid unscrupulous craftsmen and excessive spending. Remember that correct diagnostics saves budget and time.
Diagnostics of evaporator faults
Before you start disassembling the refrigerator, you need to make sure that the problem lies in the heat exchanger, and not in the thermostat or start relay. One of the main signs of a malfunction is continuous operation of the compressor. The unit hums, trying to gain temperature, but the sensors detect the heat, so the cycle is not interrupted. This may indicate that the refrigerant has leaked through a microcrack and the circulation of freon in the system is impaired.
Visual inspection often helps to identify obvious defects. If you see bulges on the back wall inside the freezer or characteristic yellow oil stains on the floor under the refrigerator, this is almost guaranteed to indicate a breakdown in the circuit. The oil comes out along with the gas, since it is under pressure in the system. It is also worth paying attention to the condition of the seals and the absence of freezing only in certain areas.
⚠️ Attention: If you find traces of oil or smell a specific solvent odor, under no circumstances try to simply turn on the refrigerator again. Operating a compressor without freon and oil can lead to its wedge and complete failure, which will make repairs economically unfeasible.
Another test method is to listen to the operation of the system. During normal operation, after turning off the compressor, you can hear a quiet gurgling or hissing sound, which indicates the movement of freon. If there is deathly silence and the engine is hot, it means there is no gas in the system. Sometimes the cause may be clogged capillary tube, but the symptoms are very similar to a leak, so without a pressure gauge it is difficult to accurately determine the cause.
Preparing tools and selecting spare parts
For successful To replace the evaporator, you will need not only a new part, but also a whole arsenal of special tools. A standard home craftsman's kit will not work here, since the work is carried out with copper tubes and inert gases. You will definitely need a gas torch with solder (usually silver or copper-phosphorus solder is used), a pipe cutter, a pipe end flarer and, most importantly, a vacuum pump.
The choice of the evaporator itself is a critical moment. Modern refrigerators often use foam evaporators built into the case, but most repairable models (especially older or commercial ones) use mounted aluminum or copper heat exchangers. When purchasing, pay attention to the geometric dimensions and method of fastening. Aluminum evaporators cheaper, but require a special flux for soldering, since aluminum oxidizes instantly in air.
Don't forget to purchase a filter-drier. This is a consumable material that required changes whenever the circuit is opened. The old filter has already absorbed moisture from the atmosphere, and if it is not replaced, the remaining moisture will turn into an ice plug in the capillary pipe, and the refrigerator will stop cooling again after a few days or weeks of operation.
Dismantling the old heat exchanger
The dismantling process begins with completely disconnecting the unit from the power supply and defrosting. Even if there is visually no ice, moisture in the pores of the insulation can interfere with operation. After this, the back panel of the freezer compartment (or the inner lining, depending on the design) is removed. Your task is to gain access to the entry point of the evaporator tubes into the housing and to the heat exchanger itself.
The next stage is unsoldering the tubes. Special caution is needed here. Copper conducts heat very quickly, and if you heat a joint for too long, you can melt the solder at adjacent joints or burn through the thin wall of the tube. Use thermal protective pastes or damp rags to isolate adjacent areas. After desoldering, the old evaporator is carefully removed; often for this you have to bend the plastic box or remove the shelves.
It is important to thoroughly clean the ends of the condenser and capillary tubes that remain in the system from oxides and old solder. The surface must be clean and shiny to ensure a good seal of the new connection. If threaded connections are used (in some models), make sure that the threads are not stripped and the sealing gaskets are replaced with new ones.
☑️ Preparation for dismantling
Installing a new evaporator and soldering
Installation of a new part begins with fitting. Make sure the evaporator fits snugly and is not pinched anywhere or touching any sharp plastic edges that could damage the thin tubes in the future. Often, the back of factory evaporators already has a layer of adhesive applied or there are mounting pads. If they are not available, use special heat-resistant glue or double-sided tape for refrigeration equipment, but not ordinary office tape.
The most crucial moment is soldering the connections. The technology is different for aluminum and copper. If you are connecting a copper tube to an aluminum evaporator (steel-aluminum or copper-aluminium), you will need a special insert or a bimetallic tube, since these metals are extremely difficult to solder directly and do not last long. Heat the joint evenly, introducing solder into the joint until it flows into the gap under the action of capillary effect.
⚠️ Attention: Do not allow an open flame to come into contact with the plastic elements of the refrigerator body. Use a metal shield or asbestos plate to protect the plastic while soldering. The plastic melts instantly, and it will be difficult to restore its integrity.
After soldering all connections, you need to install a new filter drier. It is mounted at the outlet of the condenser in front of the capillary tube. Pay attention to the refrigerant flow direction arrow stamped on the filter housing - it should point towards the capillary tube. The filter is also soldered quickly so as not to overheat its filler inside.
The secret of high-quality soldering
For a perfect seam, use nitrogen purge. If you run nitrogen through the tubes during soldering, scale does not form inside, which can subsequently clog the capillary. Nitrogen is rarely used at home, but it is useful to know about its necessity.
Evacuating and charging with refrigerant
You cannot simply assemble the system and start the compressor - air and moisture remain inside. The air contains water vapor, which when frozen will turn into ice and clog the system. Therefore, the vacuum stage is mandatory. A vacuum pump is connected to the service connection (which you should have previously installed on the process pipe of the compressor).
The process of pumping out air takes from 15 to 30 minutes, depending on the power of the pump. The pressure in the system should drop to a deep vacuum. This allows all the moisture remaining in the oil and on the walls of the tubes to boil away at low pressure. Only after this can you start refueling.
Refueling is done strictly by weight. The nameplate (technical sticker) inside the refrigerator or on the compressor indicates the exact amount of refrigerant in grams (for example 120 g). Using a weight cylinder is the only correct method. Filling “by eye” or by pressure, as amateurs do, will lead to either underfilling (bad cold) or overfilling (liquid water hammer for the compressor).
| Refrigerant Type | Balloon color | Refill Features | Boiling pressure (approximate) |
| :--- | :--- | :--- | :--- |
| R134a | Light blue | Refillable only in liquid phase (cylinder up) | Low |
| R600a (Isobutane) | Red | Explosive! Work in a ventilated area | Low |
| R12 (Obsolete) | White | Not used in new models, requires oil change | Average |
| R404a | Orange | Often used in freezers, gas mixture | High |
Checking leaks and starting
After refueling, you must make sure that there are no leaks anywhere. The simplest and most accessible method is to use a soap solution. Apply thick soap suds to all solder joints and joints. If at least one bubble appears and grows, it means the seal is broken. In this case, the freon needs to be released, the joint redone and the evacuation procedure repeated.
It is also worth using a leak detector - an electronic device that reacts to refrigerant vapors in the air. It allows you to find microscopic leaks that are invisible to the eye. After confirming the tightness, the refrigerator is connected to the network. The first cycles of operation can be long until the temperature conditions in all chambers stabilize.
Monitor the operation of the unit during the first day. Pay attention to the uniform freezing of the new evaporator (if it is a No Frost freezer, there is a fan running and frost should not be visible). If the compressor begins to cycle (frequently switches on and off) or heats up excessively, perhaps the amount of freon is selected incorrectly or there is air left in the system.
How long does it take to completely replace the evaporator?
In a workshop with ready-made equipment and spare parts, the process takes from 2 to 4 hours. At home, without experience, this can take a whole day, including time to find tools and dry the system.
Is it possible to use a universal evaporator?
Yes, there are universal evaporators (“weeping” or for No Frost), which can be cut to size. However, their effectiveness may differ from the original, which will lead to a change in temperature or increased noise.
Why did a whistle appear after replacement?
A whistle usually indicates gas leakage through a microscopic hole or a poor-quality connection. The throttle (capillary tube) may also whistle if the pressure in the system is too high due to an overdose of freon.
Is it necessary to change the oil in the compressor?
When replacing the evaporator normally, the oil does not change unless there is severe overheating or contamination of the system. However, if a lot of air and moisture got into the system for a long time, the oil could oxidize, and then its replacement is desirable.