A sudden cessation of cooling in the refrigerator compartment often becomes an unpleasant surprise, especially when food begins to melt in the freezer. If the compressor runs continuously, hums, but there is no cold, or it turns on for a couple of minutes and turns off with a characteristic click, there is a high probability that a plug has formed in the refrigerant circulation system. These are classic symptoms of blockage capillary tube —the thinnest channel responsible for throttling freon.
The capillary tube has an internal diameter of less than a millimeter, so even a microscopic oxide particle, copper shavings or a clot of frozen oil can completely block the current refrigerant. Unlike everyday problems such as improper defrosting or a malfunction of the thermostat, this defect requires intervention in the sealed circuit. Independent repair in this case it is possible, but requires special tools and strict adherence to technology, since the work is carried out with high pressure and chemically active substances.
Before you begin dismantling the unit and soldering, you need to be sure of the diagnosis. Incorrectly opening the system unnecessarily will result in the loss of expensive refrigerant and moisture ingress, which will complicate repairs many times over. In this article, we will analyze the physics of the process of blockage formation, methods for their diagnosis and a step-by-step algorithm for restoring the permeability of the system with the replacement of the filter-drier.
Symptoms of complete and partial blockage of the system
The first sign of trouble in the circulation system is a change in the temperature regime of the compressor. If completely clogged capillary tube the unit may work constantly, trying to gain temperature, but the evaporator will remain warm. In some cases, the motor-compressor heats up to critical temperatures, and then the thermal relay opens the circuit, making a loud click. After cooling, the cycle is repeated.
Partial blockage is less aggressive, but also significantly affects efficiency. The refrigerator may freeze, but the operating cycle will be unnaturally long. For example, instead of 15 minutes of operation and 45 minutes of rest, the unit will hum for 40 minutes and rest for 20. This indicates that throughput the system is reduced, and the compressor is forced to compensate for the lack of circulation with increased operating time.
⚠️ Attention: If You hear a gurgling or hissing sound inside the cabinet immediately after the compressor stops, this may indicate that the freon is on one side of the blockage. The absence of sounds of gas flow in normal mode is also an indirect sign of obstruction of the circuit.
An additional indicator is the temperature of the condenser (grids at the back or on the sides). During normal operation, it should be warm or hot evenly over the entire area. If, when the compressor is running, only the first part of the grille is hot, and then it is cold, it means that the freon does not pass beyond the blockage point. Pressure in the system on the discharge side it will be abnormally high, which creates an excess load on the compressor seals.
Reasons for the formation of traffic jams in capillary
Understanding the nature of the blockage is critical for choosing a removal method. In the refrigerator system, being closed and sealed, there seems to be nowhere for foreign substances to come from. However, there are three main factors leading to the formation of plugs in the capillary tube. The first and most common reason is moisture getting inside the circuit. Water can penetrate through microcracks due to poor-quality soldering, depressurization, or if the refrigerator has been standing for a long time with the tubes open. In the low temperature zone (exit from the capillary to the evaporator), water freezes, forming an ice plug. Periodically, it may thaw when the compressor turns off, creating the illusion that the unit is either working or not working. capillary tube.
The first and most common reason is moisture getting inside the circuit. Water can penetrate through microcracks due to poor-quality soldering, depressurization, or if the refrigerator has been standing for a long time with the tubes open. In the low temperature zone (exit from the capillary to the evaporator), water freezes, forming an ice plug. Periodically, it may thaw when the compressor turns off, creating the illusion that the unit is either working or not working.
The second reason is the products of oxidation and breakdown of the oil. When the compressor overheats or is used for a long time, mineral oil it can change its properties, thicken and precipitate. This paraffin or resinous deposit accumulates in the narrowest place - just in the capillary. Also, copper shavings remaining after poor-quality previous repairs or manufacturing defects can get there.
Is it possible to prevent blockages?
It is difficult to completely prevent blockages in an old refrigerator, but regular defrosting (at least once a year) and the absence of overheating of the compressor (cleanliness capacitor at the rear) extend the life of the system. Avoid frequent switching on immediately after defrosting - give the oil time to drain into the crankcase.
The third reason lies in poor-quality refrigerant or oil poured during a previous repair. If materials that do not meet the manufacturer's specifications were used (for example, oil of different viscosity or freon with impurities), the chemical reaction can lead to the formation of solid fractions. Filter drier in such cases it clogs the fastest, but if it allows particles to pass through, they get stuck in the capillary.
Necessary tools and preparation for repair
Repair of the refrigerant circulation system cannot be performed using a standard set of household tools. You will need specialized equipment to work with refrigeration systems. Without it, high-quality removal of the blockage is impossible, and an attempt to “blow out” the system with your mouth or a car compressor will only drive moisture and dirt deeper.
To complete the work you will need:
- 🛠️ Vacuum pump —necessary to remove air and moisture vapor from the system before refueling.
- 🛠️ Gauge station — for monitoring pressure when purging and filling (red and blue pressure gauges).
- 🛠️ Nitrogen cylinder —used to create high pressure when purging the system (pressure testing).
- 🛠️ The burner (gas or oxygen-acetylene) and solder with flux for soldering copper tubes.
- 🛠️ New filter-drier is a disposable element, the replacement of which is required when the circuit is opened.
It is also necessary to prepare a new refrigerant (the brand is indicated on the compressor nameplate, usually R134a or R600a) and scales for accurate dosage. Do not forget about safety precautions: it is better to carry out work in a ventilated area, since some gases displace oxygen, and an open flame in combination with freon can produce toxic combustion products.
Diagnostics: how to accurately find the location of the blockage
Before you start soldering, you need to localize the problem area. Professionals use the method of alternately cutting off contours. First, the process tube of the compressor is opened (usually in the middle of the housing), and it is checked whether there is freon pressure there. If the gas comes out with a hiss, it means that the circuit is sealed, and the problem is in circulation, and not in leakage.
Next, the condenser is sealed off from the filter-drier. If, when the compressor is turned on, a powerful flow of gas flows from the condenser pipe, it means that the compressor itself and the area up to the filter are working properly. The problem lies either in the filter or in the capillary tube. If there is no flow even with the condenser disconnected, it means that the compressor itself or the compressor valves are clogged. the discharge pipe or compressor valves.
The most accurate method is to use nitrogen under pressure. By connecting a nitrogen cylinder through a reducer to the system, you can apply a pressure of 10-15 atmospheres. If the pressure on the pressure gauge is maintained, but the gas does not pass through the capillary (which can be checked by ear or by lowering the end of the tube into the oil), the blockage is confirmed. Nitrogen also helps push out light contaminants if they are not compressed into a monolith.
☑️ System diagnostics
Technology for purging the system with nitrogen
Nitrogen purging is the main method of combating oil and paraffin plugs. The essence of the method is to create short-term high pressure, which cuts and pushes contamination out of a narrow channel. Important: never use air from a compressor or cylinder for purging, as it contains moisture, which will freeze and aggravate the situation.
The process is as follows: nitrogen is supplied in the opposite direction (from the evaporator or condenser, depending on where it is more convenient to cut off the section) with the filter-drier disconnected. The pressure is raised smoothly to 15-20 atmospheres. A sudden release of pressure often helps to “shoot” the plug out. The procedure is repeated several times for different sections of the circuit.
The table below shows approximate pressure parameters for different stages of work:
| Stage of work | Gas type | Pressure (atm) | Purpose |
|---|---|---|---|
| Primary check | Nitrogen | 5-7 | Search for large leaks |
| Capillary purge | Nitrogen | 15-20 | Removing oil plugs |
| Crimping the system | Nitrogen | 10-12 | Controlling the tightness of seams |
| Vacuuming | - | -0.98 (bar) | Removing moisture and air |
If patency is not restored after repeated blowing, a more radical method is used - warming up. A section of the capillary tube (usually the entrance to the evaporator) is carefully heated with a torch to the melting temperature of the solder, while simultaneously supplying nitrogen. This helps soften the hardened butter. However, with this method you need to be extremely careful not to burn out the thin tube.
⚠️ Attention: When heating the capillary tube with an open flame, use a flame spreader or heat through a metal plate. Local overheating of copper leads to its burnout and the formation of a fistula, which will require replacement of the entire evaporator.
Replacing the filter-drier and assembling the system
After successful purging and restoration of patency capillary tube, it is strictly forbidden to use the old filter-drier. Its sorbent is already saturated with moisture and dirt, and it will instantly become clogged again. The filter is a disposable element. Before installing a new filter, solder one of its sides to minimize contact with atmospheric air.
Installation is quick. The tubes are cleaned, inserted into the filter nozzles with a small gap (1-2 mm) and sealed. It is important not to overheat the filter housing, as there is a plastic mesh inside and a temperature-sensitive chemical composition. After soldering all connections, the system is assembled into a single circuit.
The next critical stage is vacuuming. A vacuum pump is connected to the system, and pumping out the air lasts at least 30-40 minutes. The residual pressure should tend to a deep vacuum. This is necessary to evaporate microscopic drops of moisture that might remain inside. Only after this is refrigerant refilled through the filling fitting, monitoring the weight on electronic scales according to the compressor data sheet. refrigerant through the filling fitting, monitoring the weight on electronic scales according to the compressor’s passport data.
Prevention of repeated blockages
After carrying out complex repairs to remove the blockage capillary tube, it is important to understand that the system has been subjected to stress. To extend the life of a repaired refrigerator, you must follow a number of operating rules. First of all, this concerns the regularity of defrosting. Even in No Frost systems, complete defrosting is recommended once a year to remove hidden moisture.
Keep the condenser (grid at the back) clean. Dust and pet hair act as a heat insulator, causing the compressor to wear out and overheat. Overheating of the oil is the main enemy of the system, leading to its coking. Regular dry cleaning of the back wall with a vacuum cleaner or brush significantly reduces the risks.
It is also worth paying attention to the stability of the voltage in the network. Voltage surges can lead to incorrect operation of the starting equipment and frequent compressor starts, which also contributes to oil degradation. Installing a voltage stabilizer for refrigeration equipment is a reasonable investment in the longevity of the equipment.
Is it possible to break through the blockage without nitrogen and a vacuum degasser?
In emergency cases, when there is no equipment at hand, some craftsmen try to blow out the system with their mouth (through a tube) or use a bicycle pump. This is extremely ineffective and dangerous. The pressure of 2-3 atmospheres, which can be created in this way, is not enough to pierce a dense oil plug in a capillary with a diameter of 0.5-0.8 mm. In addition, the exhaled air contains moisture, which will only worsen the problem. Without a vacuum sealer, it is impossible to remove this moisture, and after a couple of days an ice plug forms.
How much does it cost to replace a capillary tube?
The cost consists of the price of materials (copper tube, filter, freon) and the work of the craftsman. The tube itself is inexpensive, but replacing it is labor-intensive: it requires evaporating the old freon, dismantling the old tube (often it is glued to the evaporator), welding in a new one, vacuuming and refilling. In service centers, such a service is classified as a medium or complex repair.
Why does the blockage recur after a year?
If the blockage recurs, it means that the root cause has not been eliminated. Either there is moisture left in the system due to poor vacuum, or the compressor continues to “drive” oil due to wear on the piston group, or a low-quality filter drier was used. In rare cases, the cause is chemical incompatibility of previously used oils and freons.