A sudden increase in temperature in the freezer or lack of cold in the main compartment often causes the owner of the refrigerator to panic. However, before calling a technician or writing off the unit, it is worth considering one of the most common reasons - a malfunction in the refrigerant circuit. Capillary tube is a key element of the system responsible for throttling and supplying freon to the evaporator, and its clogging or mechanical damage completely stops cooling.
Diagnostics of this part requires attentiveness, a basic set of tools and an understanding of the principles of operation of the refrigeration circuit. Unlike replacing a lamp or seal, checking a sealed system involves high pressures and requires safety precautions. In this article, we will look at how to identify the problem, what tools will be needed and whether it is worth taking on do-it-yourself repairif you find signs of capillary blockage.
Correct identification of a fault at an early stage can save the compressor from overload and costly replacement. Ignoring the symptoms of a blockage often leads to the fact that refrigerant stops circulating, and the motor begins to work without stopping, trying to reach the set temperature, which ultimately disables it.
Principle of operation and the role of the capillary tube in the system
The capillary tube is a long, small-diameter copper tube that connects the condenser and evaporator. Its main task is to create hydraulic resistancenecessary for a sharp pressure drop. It is thanks to this difference that the liquid refrigerant, leaving the condenser under high pressure, boils and turns into a gaseous mixture, actively absorbing heat from the refrigerator chambers.
In modern models, such as Indesit or Atlant, the length The capillary can reach several meters, although outwardly it looks compactly curled into a spiral. The diameter of the internal hole is a fraction of a millimeter, which makes the system extremely sensitive to any foreign inclusions. Even a microscopic particle of oxide or moisture can be fatal to the circulation of freon.
The throttling process occurs continuously while the compressor is running. If the patency of the tube is disrupted, the pressure at the inlet to the evaporator drops, and at the outlet from the condenser, on the contrary, increases. This creates an emergency operation mode for the compressor, which tries to push gas through the obstacle, consuming increased current.
Main signs of capillary blockage or damage
It is possible to determine that the problem lies in the capillary tube by a number of indirect signs that appear during operation of the unit. The very first signal is usually a change in temperature: the food in the freezer begins to thaw, and the refrigerator compartment becomes warm, although the compressor hums continuously.
The second important symptom is the temperature regime of the compressor itself and the condenser grill. During a normal cycle, the grill at the back of the refrigerator should be hot evenly. If you observe that only part of the grate is hot, and the rest remains cold, or the compressor is heating up to a state where it is impossible to touch it, this is a sure sign hydraulic resistance in the circuit.
- 🔊 The compressor works without interruptions, without turning off for rest, while the hum may become more strained or intermittent.
- ❄️ The evaporator inside the freezer is covered with frost unevenly or remains completely cold, although the motor is running.
- 🔥 The condenser (rear grill) heats up only at the beginning of the section, then the tubes remain at room temperature.
It is also worth paying attention to the filter drier, which is installed in front of the entrance to the capillary tube. If it is covered with frost or, conversely, has traces of oily smudges, this indicates that the system is trying to compensate for the loss of performance. In some cases, with a complete blockage, you can hear a characteristic gurgling or hissing sound that freon makes, trying to overcome the obstacle.
Necessary tool for diagnostics and repair
Before proceeding with physical intervention in the system, it is necessary to prepare a specialized tool. Working with the refrigeration circuit does not allow for improvisation, as it requires creating a vacuum and working with gas under pressure. The master's basic kit includes not only screwdrivers, but also specific equipment.
To check the integrity and patency of the capillary tube, you will definitely need a cylinder with nitrogen and a reducer. It is nitrogen that is used for purging and crimping, since it is inert and does not contain moisture, unlike compressed air from a compressor, which can only aggravate the situation by introducing water into the system.
In addition, for high-quality repairs you will need a torch (gas or oxygen-propane), solder for copper pipes and, of course same, new filter drier. Changing the filter when opening the circuit is a mandatory rule, ignoring which will lead to re-clogging in a short time.
- 🔧 Manometric station (manifold) for monitoring pressure when pumping nitrogen and vacuuming.
- 🔥 Blowtorch or torch with a set of solder (silver or copper-phosphorus).
- 💨 Vacuum pump to remove moisture and air from the system before refueling.
Do not forget about personal protective equipment. When working with open flames and metal, there is a high risk of burns, and in the event of a possible refrigerant leak (although there is little of it in household refrigerators), it is important to ensure good ventilation of the room.
☑️ Preparation for diagnostics
Methods for checking the patency of a capillary tube
There are several ways to check the condition of the capillary, but the most reliable is the purging method nitrogen. Before starting the procedure, the refrigerator must be unplugged and completely defrosted. An initial visual inspection helps to identify obvious mechanical damage, kinks or traces of corrosion on copper tubes.
To carry out the test, it is necessary to disconnect the capillary tube from the filter drier and from the inlet to the evaporator. After this, a hose from a nitrogen cylinder is connected to one of the ends. The pressure should be increased gradually while watching the pressure gauge. If the capillary is clean, you will hear a characteristic gas flow coming out from the other side, and the pressure in the system will remain stable after closing the valve.
⚠️ Attention: Never try to blow out the capillary with your mouth or use a car compressor without filtration. Introducing moisture or oil into the thinnest channel will lead to the formation of an ice plug or a chemical reaction that will completely disable the refrigerator.
If, when nitrogen is supplied, the pressure rises sharply and the gas does not pass, this indicates solid blockage. In such a situation, you often have to change the tube completely or try to pierce it with a hydraulic press (which requires high qualifications). Sometimes the blockage can be eliminated by heating the problem area with a burner while simultaneously supplying nitrogen, but this method is risky and can damage the thin walls of the tube.
Table for diagnosing circuit malfunctions
For the convenience of systematizing symptoms and possible causes, we have compiled a table that will help compare observable signs with probable breakdown. This will allow you to more accurately determine whether the capillary tube needs to be replaced or whether the problem lies in another unit.
| Symptom | Probable cause | Action |
|---|---|---|
| Compressor hot, cold end capillary | Clogged capillary tube | Purge with nitrogen, replace the filter |
| Frost only at the entrance to the evaporator | Partial blockage or moisture | Evacuate, replace dryer |
| Compressor does not start, relay clicks | Faulty start relay or motor | Checking the electrical circuit |
| There is cold, but the compressor does not turn off | Freon leakage or compressor wear | Searching for leaks, measuring pressure |
By analyzing the data from the table, you can to conclude that the combination of a hot compressor and a cold start of the capillary is an almost 100% indicator of a problem in this particular unit. However, the final diagnosis is made only after an instrumental pressure check.
Why can’t you use air for purging?
Atmospheric air always contains moisture. When compressed and entering the cold zone of the refrigeration circuit, this moisture turns into ice, which tightly clogs the capillary. In addition, oxygen at high soldering temperatures can oxidize copper from the inside, creating scale, which will also cause future blockage.
Replacing the filter drier and restoring the system
If the check confirmed the blockage, or if you simply opened the circuit for diagnostics, replacement filter-drier becomes mandatory. This element is responsible for trapping microscopic debris and, more importantly, absorbing moisture. An old filter that has been exposed to air is already saturated with moisture and will not be able to perform its functions.
The replacement process begins with carefully sawing off the old filter. It is important not to overheat the tubes during dismantling, so as not to damage adjacent elements. The new filter is installed strictly in accordance with the flow direction indicated by the arrow on the housing. Soldering should be done quickly to minimize copper oxidation, using flux and high-quality solder.
After installing a new filter and checking the capillary for permeability, the system must be evacuated. This is a critical step that is often ignored by hobbyists. Vacuum pump removes air and evaporates moisture from the walls of the tubes. The evacuation time should be at least 15-20 minutes, after which you need to check the system for leaks by clamping the tube and observing the pressure gauge.
⚠️ Attention: Filling the refrigerator with freon without prior deep evacuation will cause the remaining air and moisture to mix with the refrigerant. This will cause corrosion of the internal parts of the compressor from the inside and the formation of acids that will corrode the motor windings within several months.
Typical mistakes during self-repair
Refrigeration circuit repair is an area where the cost of an error is extremely high. Independent attempts often end in complete loss of the unit due to incorrect actions. One of the most common mistakes is neglecting cleanliness when soldering. Scale or dust that gets inside the tube instantly becomes a center of crystallization for a new blockage.
Another common mistake is incorrect selection of the length and diameter of the capillary tube when replacing. Hydraulic resistance systems are calculated by engineers with an accuracy of a millimeter. Installing the tube “by eye” or “just to fit” will lead to the compressor operating in abnormal mode: either there will not be enough performance, or water hammer will occur.
- 🚫 Using unsuitable solder, which melts at too low temperatures and can leak during operation compressor.
- 🚫 Insufficient vacuuming time, leaving moisture in the system.
- 🚫 Ignoring the replacement of the filter-drier after opening the circuit.
It is also worth mentioning the error of saving on tools. An attempt to do without a pressure gauge station and work “by touch” in a system where pressure is measured in atmospheres and bars is unacceptable. Without instruments, you will not be able to control the filling process and diagnose anomalies in real time.
When to turn to professionals
Despite the detailed instructions, there are situations when the intervention of a professional is the only reasonable solution. If you are not confident in your skills in soldering non-ferrous metals or do not have access to specialized equipment (vacuum machine, scales for freon), it is better not to risk it. Repairing a refrigerator can cost more than calling a technician.
This is especially true for refrigerators running on isobutane (R600a). This refrigerant is explosive at certain concentrations in air. Working with it requires not only special equipment, but also compliance with strict safety regulations, the presence of non-sparking tools and good ventilation.
⚠️ Attention: If you smell gas when working with an R600a refrigerator, stop work immediately, open the windows and eliminate any sources of spark. In such cases, independent repairs are strictly prohibited.
It is also worth considering calling a specialist if, after your manipulations, the refrigerator does not work or begins to behave strangely (loud knocking, vibration). A professional technician will be able to carry out in-depth diagnostics, determine whether the compressor has suffered damage from operating in emergency mode, and provide a guarantee for the work performed.
Is it possible to clean a capillary tube without nitrogen?
Theoretically, there are methods of washing with special solvents under pressure, but in domestic conditions they are ineffective and dangerous. Without nitrogen, it is impossible to create the necessary pressure and guarantee the absence of moisture. Using compressed air from a compressor will only drive moisture and oil deeper into the system, which will lead to irreversible consequences.
How much does it cost to replace a capillary tube in a service?
The cost consists of the price of materials (pipe, filter, freon) and the work of the technician. On average, repairs cost 30-50% of the cost of a new refrigerator. The exact price depends on the model of the unit, the type of refrigerant and the complexity of access to the unit.
How often do you need to change the filter-drier?
The filter-drier is a consumable item, but only when the sealed circuit is opened. Under normal operation, without leaks or repairs, it lasts the entire life of the refrigerator (10-15 years). A planned replacement without reason is not required.
Why does the refrigerator freeze worse after replacing the capillary?
Most likely, the length or diameter of the new tube was chosen incorrectly. Every millimeter of length affects the resistance to freon flow. Also, the cause may be poor-quality evacuation or excess/lack of refrigerant charged.
Is it dangerous to solder refrigerator tubes yourself?
Soldering requires skills in working with open fire and flammable gases. The main risk is fire or burns. In addition, when working with R600a refrigerant, there is a risk of explosion if there is a spark. If you have never held a burner in your hands, it is better not to start training on a working refrigerator.