The situation when the refrigerator stops freezing, but the compressor runs continuously or turns on for short periods of time, often confuses the owner. An externally serviceable unit may not gain cold due to a disruption in the circulation of refrigerant in the system. One of the most common causes of such a malfunction is clogging of the capillary tubewhich serves as a throttling element of the circuit.
Understanding the operating principle of this unit helps to quickly identify the problem without calling a technician. The capillary tube is a long copper coil of very small diameter that creates the necessary resistance for the transition of freon from a liquid to a gaseous state. It is here that a sharp drop in pressure occurs, ensuring cooling of the evaporator. If the patency of the tube is disrupted, the entire circulation cycle stops, and the refrigerator turns into an ordinary cabinet.
Diagnosis of this malfunction requires care and compliance with safety precautions, since the system is under pressure. In this article, we will look at how to distinguish a blockage from other breakdowns, what tools are needed to check, and whether you can deal with the problem yourself. You will learn about methods for purging, flushing and replacing the element, as well as how to prevent reoccurrence.
Symptoms of impaired refrigerant circulation
The first sign indicating problems in the heat removal system is a change in the temperature regime inside the chambers. If you notice that the food in the freezer has begun to thaw, and the refrigerator compartment has become warm, you should listen to the operation of the motor. When clogged capillary pipeline the compressor often runs idle, trying to build up pressure, but the circulation of gas along the circuit is absent or very difficult.
It is important to pay attention to the nature of the compressor operation. Unlike a working refrigerator, which turns on and off at regular intervals, when clogged, the engine can hum continuously, heating up to high temperatures. Sometimes it can start for a few seconds and immediately stall due to the activation of the thermal protection relay. This happens because the pressure at the outlet of the compressor reaches critical values, but at the inlet remains low.
⚠️ Attention: If the compressor runs continuously for more than an hour, and the condenser (grid at the back) remains only partially cold or warm, this is a sure sign of a lack of freon circulation. Do not leave the equipment in this state for a long time, so as not to burn the motor windings.
Another symptom may be the appearance of swelling or, conversely, a complete lack of heating in certain areas of the evaporator. If you carefully lift the plastic panel inside the freezer (where the evaporator is located), it should be evenly frosted or cold during normal operation. If the tube is clogged, freon does not enter the evaporator in the required volume, so cooling will be absent completely or observed only at the very entrance to the tube.
Visual and tactile diagnostics of the system
Before proceeding disassembling the unit and working with tools, it is necessary to carry out initial diagnostics. It consists of inspecting the external elements of the refrigeration circuit. First of all, check the integrity of the tubes leading to the compressor. The absence of mechanical damage, dents or traces of oil already narrows the search range. Pay special attention to the area where the capillary tube enters the refrigerator body - this is where kinking or ice plug formation often occurs.
The tactile inspection method is one of the most informative for the technician. With the compressor running, gently touch (be careful, it may be hot!) the condenser and the pipes coming from the compressor. Normally, the discharge tube should be hot and the suction tube should be cold. If the discharge tube becomes red hot or becomes excessively hot immediately at the outlet of the compressor, and then cools down sharply, this indicates that the gas is not passing through the capillary. It is also worth inspecting the filter drier. This small metal cylinder, installed in front of the capillary tube, serves to clean freon from moisture and impurities. When the system is clogged, the filter often becomes covered with frost or, conversely, remains warm when it should be at room temperature. If you see swelling of the filter housing or hear a whistling sound passing through it, it means that the passage is impaired in this particular unit or immediately behind it. capillary.
It is also worth inspecting the filter drier. This small metal cylinder, installed in front of the capillary tube, serves to clean freon from moisture and impurities. When the system is clogged, the filter often becomes covered with frost or, conversely, remains warm when it should be at room temperature. If you see a bulge in the filter housing or hear a whistling sound passing through it, it means that the patency is impaired in this particular unit or immediately behind it.
Technical reasons for the formation of blockages
Understanding the nature of the blockage helps you choose the right method for removing it. Most often, foreign substances end up in the circulation system that should not be there. The main reasons are copper oxidation products formed due to poor-quality soldering or air ingress during installation, as well as particles of burnt oil from the compressor. These solids accumulate at the narrowest point of the system - at the beginning of the capillary tube.
Another common cause is freezing of moisture inside the tube. Even a minimal amount of water that enters the circuit during refueling or due to a leak turns into an ice plug when passing through a low-pressure zone. This “water hammer” or ice jam completely blocks the movement of the refrigerant. You can distinguish an ice plug from mechanical debris by frequency: the ice can periodically thaw when the compressor stops, and the refrigerator will begin to freeze for a short time, after which it will stop again.
Below is a table that helps classify the type of blockage according to indirect signs:
| Type of blockage | Cause occurrence | Characteristic symptom | Elimination method |
|---|---|---|---|
| Mechanical | Copper oxides, dust, chips | Permanent blocking, no response to cycles | Nitrogen purging, tube replacement |
| Ice plug | High humidity in the circuit | Periodic restoration of operation after defrosting | Evacuation, filter replacement |
| Paraffin | Poor quality oil or freon | Thickening at low temperatures | Flushing the system, replacing the refrigerant |
| Complex (mixed) | Long-term operation without maintenance | Partial reduction in cooling capacity | Full flushing and vacuuming |
It is worth noting that the use of low-quality consumables during previous repairs significantly increases the risk of re-clogging. If the system was filled Freon with impurities or oil of the wrong viscosity was used, the formation of sediment in the capillary is only a matter of time. Therefore, when making repairs, it is important to use only original or certified components.
Necessary tools and preparation for repairs
To independently determine and remove a clogged capillary tube, you will need a specialized tool. Without it, it is impossible to carry out high-quality diagnostics and repairs. First of all, you will need a vacuum pump, which is necessary to create a deep vacuum in the system and remove moisture. A cylinder with dry nitrogen is also required, since it is strictly forbidden to blow the system with ordinary air due to the moisture it contains.
In addition, for work you will need:
- 🔧 Gas burner or a blowtorch for soldering copper tubes.
- 📏 Gauge station for monitoring pressure during refueling and purging.
- 🧪 Filter-drier new sample (be sure to change it whenever the circuit is opened).
- 🔪 Pipe cutter for neat separation of copper lines.
- 🛢️ Oil for the compressor (if flushing of the system is required).
Preparation of the workplace also plays an important role. Ensure good ventilation in the room, as soldering and possible release of freon may release harmful substances. Prepare a container in advance to collect old oil from the compressor. Remember that working with refrigerants requires caution, and in some countries a license is required to handle freon.
⚠️ Attention: Never use car compressors or tire pumps to purge the system. They are not able to create the necessary pressure and, more importantly, will drive moisture and oil into the system, which will completely damage the refrigerator.
☑️ Preparation for diagnostics
Methods for checking the patency of a capillary tube
There are several ways to determine exactly where the blockage is located. The easiest method is to disconnect the capillary tube from the filter drier and try to blow it out with your mouth. If air passes through with great difficulty or does not pass at all, it means that the blockage is localized in the tube itself. However, this method does not guarantee cleanliness and does not allow assessing the condition of the entire system, so it is considered rather preliminary.
A more professional approach involves the use of nitrogen under pressure. After unsoldering the condenser from the filter drier, a pressure gauge is connected to the compressor fitting, and nitrogen is supplied to the capillary outlet. The pressure is raised to 10-15 atmospheres. If the pressure gauge needle is a dead weight and does not go down, there is no patency. If the pressure drops slowly, the blockage may be partial or the tube is simply very long and narrow.
You can use the heating method to check for ice blockage. The exit point of the capillary tube from the housing (entrance to the evaporator) is carefully heated with a hair dryer or warm water. If, after warming up, the refrigerator starts to work normally, and after a while it stops again, it means that moisture is circulating in the system, which freezes in a narrow section. In this case, not just cleaning is required, but complete vacuum drying of the circuit.
What to do if nitrogen does not pass through?
If there is no passability when nitrogen is supplied under a pressure of 15 atmospheres, try disconnecting the capillary tube from the evaporator and blowing it out separately. If the tube is clean, then the blockage is in the evaporator itself or at the connection point. Often, a “pocket” of oxides forms in this place, which can only be removed by replacing a section of the tube or the entire evaporator.
Technology for removing blockages and prevention
The process of eliminating blockages depends on its type. If the problem is caused by mechanical particles, backflushing is an effective method. To do this, the tube is disconnected on both sides and nitrogen is supplied in the direction opposite to the refrigerant flow. The pressure can reach 30 atmospheres, which allows you to knock out a stuck plug. However, this method is risky and can damage the thin walls of the tube.
The most reliable method is considered to be flushing the system with a special solvent or alcohol, followed by prolonged drying with a vacuum pump. The procedure is as follows: flushing liquid is poured into the circuit, the system is warmed up, and then the liquid is removed along with dissolved contaminants. After this, the vacuum pump runs for several hours, removing solvent vapors and moisture. Only after this is refilled with new refrigerant oil.
In cases where cleaning is impossible or ineffective, the capillary tube is replaced. The new tube must have exactly the same parameters (diameter and length) as the original one, otherwise the refrigerator will not work correctly. After installing a new element, a pressure test with nitrogen is required to check the tightness and vacuuming.
To prevent repeated breakdowns, frequent defrosting using a hot hairdryer should be avoided. sudden changes in voltage and storing products with damaged packaging, which can lead to corrosion. Regularly cleaning the condenser from dust also helps the compressor operate in optimal mode, reducing the risk of oil overheating and carbon deposits.
Frequently asked questions (FAQ)
Is it possible to clean the capillary tube without opening it?
Clean the tube without physical access it is almost impossible to reach her. Some craftsmen try to use chemical additives poured through the Schrader valve, but this is a temporary measure, which often leads to even more serious problems, since the chemical can corrode the compressor seals.
How much does it cost to replace a capillary tube in the service?
The cost of the work depends on the model of the refrigerator and the complexity of access to the evaporator. The price usually includes the cost of a new tube, filter drier, refrigerant and the work of a technician. On average, repairs cost 30-50% of the cost of a new refrigerator, which makes it economically feasible.
Why does the refrigerator freeze but does not turn off after replacing the tube?
This may indicate an incorrect selection of the length or diameter of the new capillary tube. If the resistance is too low, the pressure in the system drops and the compressor runs without stopping. Also, the cause may be undercharging with freon or the presence of air in the system.
Is freon released during repairs dangerous?
Modern refrigerants (R600a, R134a) in small quantities contained in a household refrigerator are not toxic to humans upon short-term contact, but R600a (isobutane) is an explosive gas. Therefore, work must be carried out in a ventilated area and exclude sources of open flame.