The situation when the refrigerator compressor runs continuously, hums, but it is warm inside the chamber, often indicates a serious malfunction in the refrigerant circuit. In most cases, the cause is a blockage in a narrow section of the system known as the capillary tube. This is the critical element where the liquid refrigerant changes to a vapor state, causing sudden cooling. If the patency of this channel is impaired, the circulation of freon stops and the cooling process becomes impossible.
Before deciding on a complex cleaning procedure, it is necessary to accurately diagnose the problem, since the symptoms may be similar to a gas leak or a breakdown of the compressor itself. It is important to understand that working with the cooling system requires not only specific tools, but also strict adherence to safety precautions. Capillary blockage is not just garbage, but often the result of the reaction of moisture and oil inside the circuit, forming ice or acid plugs.
In this article we will analyze in detail the physical essence of the problem, the necessary tools for professional removal blockage and a step-by-step algorithm of actions. Self-repair is possible, but it requires care and understanding of the principles of operation of the refrigeration machine. Incorrect actions can lead to the final failure of the unit, so carefully study each stage before starting work.
Signs and causes of clogged capillary tube
You can determine that a plug has formed in the system by the characteristic signs that appear in the first hours or days after turning on the unit. The compressor starts running non-stop, trying to build up the temperature, but the evaporator either remains warm or only partially cools. In this case, the condenser grille at the back of the refrigerator may be hot only at the beginning or, conversely, remain cold, which indicates a lack of refrigerant circulation.
The main cause of blockage is moisture that entered the circuit during poor-quality repairs or depressurization of the system. Interacting with the refrigerant and compressor oil, water causes corrosion of metal walls and the formation of solid oxide particles. These particles accumulate in the narrowest place - the capillary tube, the diameter of which is less than a millimeter, completely blocking the freon current.
⚠️ Attention: Trying to defrost the refrigerator for several days sometimes helps if the plug is icy. However, if the problem returns 24 hours after complete defrosting, it means that there is moisture or solid blockage in the system that requires mechanical intervention.
The blockage can also be caused by oil breakdown products that are formed when the compressor overheats or the equipment is idle for a long time. Such “sludge” has a resinous structure and is difficult to simply blow through. The table below shows the main symptoms that help distinguish a blockage from other faults:
| Symptom | Capillary blockage | Freon leakage | Thermostat malfunction |
|---|---|---|---|
| Operation compressor | No stop, hot | Cyclic or off | No stop |
| Condenser temperature | Hot only at outlet | Cold or warm | Hot along the entire length |
| Sound when punctured | There is hissing, but weak | No hissing or very weak | Normal hissing |
| Evaporator condition | Warm or partially cold | Warm | Frozen "fur coat" |
It is important to note that in older models refrigerators that used R12 freon are more likely to form an acid blockage due to the interaction of the refrigerant with copper and steel in the presence of moisture. Modern gases R600a and R134a are less aggressive, but more sensitive to the quality of the oil and the cleanliness of the system.
Necessary tools and preparation for repair
For a high-quality restoration of the patency of the capillary tube, a conventional set of household tools will not be enough. You will need specialized equipment to create a vacuum, supply pressurized gas, and seal the copper tubes together. Without a vacuum pump and a pressure gauge station, it is impossible to carry out repairs according to modern standards.
The key element for purging is a cylinder with dry nitrogen. It is nitrogen that makes it possible to displace contaminants and moisture without oxidizing the inner walls of the tubes, as ordinary air does. The pressure during purging must be controlled by the reducer so as not to damage the evaporator or other weak components of the system.
The list of necessary equipment includes:
- 🔧 Pressure gauge station (preferably two-valve for R134a or R600a).
- 🔧 Vacuum pump to remove moisture and air from the circuit.
- 🔧 A cylinder with dry nitrogen and a reducer.
- 🔧 Gas torch (oxygen-propane or with flux) for soldering.
- 🔧 Solder (silver or copper-phosphorus) and flux.
- 🔧 Pipe cutter, brush, needle file and a new filter drier.
Before starting work, the refrigerator must be unplugged and completely defrosted. The unit is then turned over to gain access to the compressor and sealed pipes. It is important to carefully remove the plastic casing covering the motor-compressor so as not to damage the electrical contacts and wiring.
⚠️ Attention: The use of oxygen for purging or soldering is strictly prohibited! Oxygen mixed with oil vapor forms an explosive mixture. Use only inert gases (nitrogen) or dry air.
Methods for cleaning the capillary tube
There are several ways to remove blockages, the effectiveness of which depends on the nature of the plug. The simplest method—punching—is often used for initial diagnosis. If, when the filter-drier is disconnected and air is supplied to the condenser, gas freely comes out of the capillary tube, it means that the blockage is mobile or does not exist at all.
A more radical method is hydraulic cleaning. It involves the use of a solvent liquid (for example, alcohol or a special composition), which is poured into the tube under pressure. The liquid dissolves tar deposits, after which the system is thoroughly purged with nitrogen. This method is effective, but requires a complete flushing of the afterward system, since the solvent can damage the insulation of the compressor windings.
The most reliable method is to replace a section of the capillary tube. Since the length of the capillary is strictly calculated by the factory for a specific refrigerator model, you cannot simply take it and replace it with the first one you come across. However, if the blockage is localized in an accessible place (usually at the entrance to the evaporator or at the filter), you can cut out the damaged area and weld in a new piece of tube of the same diameter and length.
Technical nuances of the capillary
The capillary tube works like a choke. Its length varies from 1.5 to 4.5 meters, and its internal diameter is 0.6–0.9 mm. Shortening the tube even by 10 cm will lead to an increase in condensation pressure and overload of the compressor, and lengthening it will lead to a drop in performance and underfreezing.
In some cases, craftsmen use the “burnout” method, when the area of the blockage is carefully heated with a burner until high gas pressure breaks through the plug. This method is risky and can lead to rupture of a thin-walled tube, therefore it requires experience and precise pressure control.
Replacing the filter-drier and soldering the circuit
Any operation to open the refrigeration circuit requires a mandatory replacement of the filter-drier. This element is responsible for absorbing moisture and retaining mechanical particles. An old filter that has been exposed to air instantly absorbs moisture and, when restarted, will cause a new blockage.
The replacement process begins with carefully sawing off the old filter. It is important not to heat it with a burner, since there is zeolite inside, which when heated can release moisture into the system. A new filter is installed immediately after removing the old one in order to minimize contact of the internal cavities with the atmosphere.
When soldering connections, it is necessary to observe the temperature regime:
- 🔥 Copper melts at 1083°C, but soldering is carried out at 600-700°C.
- 🔥 Steel (compressor tube) requires higher temperatures and high-quality cleaning.
- 🔥 Solder should flow into the gap under the action of capillary effect, and not just lie on the surface.
After installing a new filter and restoring the integrity of the tubes (if they were cut for cleaning), the system must be checked for leaks. To do this, nitrogen is supplied to the circuit at a pressure of about 10-15 atmospheres (for R134a/R600a) and left for several hours. A drop in pressure will indicate the presence of microcracks or poor-quality soldering.
☑️ Check before soldering
Evacuation and refrigerant charging
After successful purging and After checking the tightness, the most important stage begins - vacuuming. The remaining moisture in the system boils at low pressure, so a deep vacuum allows it to be removed as steam. The procedure should last at least 30-40 minutes, and the residual pressure should be less than 50 microns (0.05 mm Hg).
Filling the refrigerator with refrigerant is carried out strictly according to the weight indicated on the technical sticker (usually located inside the chamber or on the back wall). The use of cylinders without scales is unacceptable, since it is impossible to determine the exact amount of gas “by eye”. An excess of freon will lead to liquid shock and breakdown of the compressor, and a deficiency will lead to ineffective operation.
The refilling process is as follows:
- Connect the freon cylinder to the pressure gauge station.
- Open the valve and start the compressor.
- Supply gas in small portions, monitoring the motor current and the temperature of the condenser.
- Solder the filling tube when the calculated amount of refrigerant has been collected.
⚠️ Attention: In refrigerators with gas R600a (isobutane), work must be carried out in good conditions ventilated area. This gas is explosive at a concentration in air of more than 1.3%. Sparking contacts of a thermostat or relay can cause ignition.
To accurately diagnose the fullness of the system, professionals use suction tube temperature (it should be slightly cool, but not covered with frost at the compressor itself) and the current consumed by the motor. These parameters give a more accurate picture than just the pressure in the system.
Typical errors and precautions
The most common mistake in self-repair is neglecting evacuation. Many amateur craftsmen simply blow the system with air and immediately refill with freon. The remaining moisture will freeze again in the capillary after a short time, and the entire repair will have to be redone.
Another mistake is the use of inappropriate materials for soldering. Brass solder or acid fluxes can cause rapid internal corrosion of copper tubing. Only silver or copper-phosphorus solders and special fluxes that do not require rinsing are suitable for refrigeration equipment.
The length of the capillary tube is often ignored when replacing it. If you cut off the clogged area, the new piece must be exactly the same length and inner diameter. Using a tube from another refrigerator "at random" will lead to an imbalance in the system and loss of cooling performance.
Excessive pressure when blowing is also dangerous. Older aluminum or stainless steel evaporators may have very thin walls. Pressure above 20-25 atmospheres can rupture the evaporator, which will turn a simple repair into a complex replacement of the internal circuit.
Frequently asked questions (FAQ)
Is it possible to clean the capillary without a nitrogen cylinder?
Theoretically, you can try to blow it with a compressor or your mouth, but the efficiency will be extremely low. You will not be able to create enough pressure to push out a dense clog and, most importantly, you will not remove moisture from the system. Without nitrogen, there is a high risk of oxidation of copper tubes from the inside during soldering.
How much does it cost to replace a capillary tube during service?
The cost consists of the work of the master, the cost of materials (freon, filter, tube, solder) and the difficulty of access to the evaporator. On average, repairs cost 30-50% of the cost of a new refrigerator, which makes it worthwhile only for high-quality models.
Why is the refrigerator louder after cleaning?
Perhaps there is air left in the system (poor vacuuming) or too much oil was poured during cleaning. Also, the cause may be poor-quality soldering, which creates turbulence in the gas flow, or damage to the vibration isolators of the compressor during installation.
How to understand that the blockage is in the capillary and not in the filter?
When the filter is clogged, gurgling or hissing is often heard in the area where it is installed. If, when the filter is disconnected from the capillary, gas flows freely from the condenser, but not through the capillary tube itself, it means that the blockage is in it. If gas does not flow anywhere, the problem may be in the condenser or discharge tube.