A decrease in cooling efficiency or a complete stop in the freezer often indicates a violation of the refrigerant circulation in the system. If the compressor runs continuously, hums, but no cold is produced, most likely there is a problem with the filter drier. This is a critical malfunction that requires immediate intervention, since prolonged operation in this mode can lead to engine combustion. clogging of the capillary tube or filter drier. This is a critical malfunction that requires immediate attention, since prolonged operation in this mode can lead to engine combustion.
Diagnostics of the cooling system requires an understanding of the physics of the processes and the presence of specialized tools. Capillary tube is a small-diameter copper pipeline that creates the necessary throttling (resistance) for the transition of freon from liquid to gaseous state. It is in this unit that oxidation products, moisture or paraffin deposits most often accumulate, blocking the gas flow.
Before proceeding with disassembling the unit and checking the tightness, it is necessary to conduct an initial visual assessment and analysis of the operation of the motor. An accurate diagnosis of “clogging” is made only after eliminating freon leaks and checking the electrical part of the compressor. In this article we Let's look at professional identification methods, tools for purging and the nuances of restoring the patency of the system.
Signs of blockage of the capillary system
The first symptom that users pay attention to is nature of the compressor operation. The engine may turn on, run for a while, and then turn off by a thermal relay, or hum continuously without reaching the set temperatures. This occurs because high pressure the compressor outlet cannot be relieved through a clogged capillary, and the motor is operating in overload.
When physically examining the condenser grill (usually located at the back of the refrigerator), uneven heating may be noticed. The top of the grate may be hot while the bottom remains cold. There is also often swelling of the side walls of the refrigerator or the appearance of a characteristic hissing sound inside the case if the blockage is partial and the gas still breaks through under pressure.
- 🌡️ The compressor works non-stop or often turns off due to overheating.
- ❄️ The freezer compartment does not freeze, although there may be a little in the main chamber cool.
- 🔊 The appearance of gurgling or hissing sounds in the area of the evaporator.
- 💥 Swelling of the back wall inside the refrigerator compartment (with a hidden evaporator).
⚠️ Attention: If you hear a loud bang and smell a burning smell, immediately unplug the refrigerator. This may indicate a critical increase in pressure or breakdown of the insulation of the compressor windings.
Necessary tools for diagnostics
To qualitatively check the patency of the capillary tube, household methods are not enough. You will need a professional refrigeration kit that allows you to create controlled pressure and monitor its changes. The main tool is nitrogen cylinderequipped with a gearbox and a pressure gauge. Nitrogen is inert and does not contain moisture, which is critical when working with the system.
A vacuum pump is also needed to remove moisture and residual gases after cleaning. If a nitrogen cylinder is not available, some technicians use a powerful automotive compressor, but this method is less effective for in-depth diagnostics and can introduce moisture into the system. Be sure to prepare a torch, solder and flux for subsequent sealing of the system.
Don't forget about personal protective equipment. Working with metal and gas under pressure requires caution. When soldering, use fire-resistant gloves and safety glasses, as solder may splatter.
Nitrogen purge test method
The most reliable way to determine a blockage is to purge the system with nitrogen under pressure. First you need to get to the capillary tube. Usually it is soldered into the evaporator or hidden in the foamed layer of the housing. If access to the tube is closed, you will have to carefully open the thermal insulation, trying not to damage the copper itself.
The verification process begins by disconnecting the capillary tube from the filter-drier. A fitting for connecting a nitrogen cylinder is installed in place of the filter. The pressure is supplied smoothly; it is necessary to monitor the pressure gauge readings. If the system is clean, the pressure will drop as gas escapes through the open end of the tube, but will not rise to critical values.
In the case of complete blockage, the pressure gauge will show a rapid increase in pressure to 10-15 atmospheres or higher, but there will be no gas escape. If the blockage is partial, you will hear a characteristic whistle of escaping air, but the pressure will remain above normal. This indicates that the cross-section of the tube is reduced by foreign substances.
☑️ Nitrogen diagnostics
⚠️ Attention: Never supply nitrogen to the system if there is old freon left in it. Freon combustion products, when in contact with an open burner flame, form phosgene, a deadly gas. First, release the refrigerant in a well-ventilated area.
Alternative method: test with a compressor
If a nitrogen cylinder is not on hand, you can use the refrigerator compressor itself to create pressure. This method is less accurate, but allows a rough estimate of patency. To do this, disconnect the suction and discharge pipes of the compressor. A hose leading to the capillary tube is connected to the discharge pipe (from where the gas comes out).
When the compressor is turned on, pressure is created at the discharge. By sticking your finger into the open end of the capillary tube (or connecting a pressure gauge there), you can feel the force of the flow. If it blows weakly or does not blow at all, and the compressor is clearly working under load (humming), it means that the permeability is impaired.
Therefore, this method is good only for initial diagnostics, when you just need to understand whether gas is flowing or not.
| Parameter | Normal condition | Sign of blockage | Sign of leakage |
|---|---|---|---|
| Nitrogen pressure | Free exit, low pressure | Increase to 10+ atm, no exit | Instant drop up to 0 |
| Flow sound | Uniform whistle | Absent or intermittent | Strong whistle at the hole |
| Heating of the tube | Uniform along the length | Hot before the blockage, cold after | Does not matter |
| Motor operation | Cyclic | Constant or shutdown due to overload | Constant (does not gain cold) |
Localization of location and types of contamination
Clogging can occur in different parts of the system, and the complexity of the repair depends on this. Most often, a plug forms in the narrowest place - inside capillary tube or in the porous filler of the filter drier. The filter retains mechanical particles and moisture, and over time its resource is exhausted.
There are two main types of blockages: mechanical and ice. Mechanical is caused by copper oxides, oil breakdown products, or solder that got inside the tube during poor installation. An ice plug is formed due to moisture that freezes in the low temperature zone (exit from the capillary to the evaporator).
To determine the type of blockage, warm the intended area with a hair dryer or hot water. If after heating the patency is restored and gas flows, this is an ice plug. If the pressure does not drop even when heated, the blockage is mechanical, and simple bleeding may not help, a section of the tube will need to be replaced.
Why does an ice plug form?
Ice blockage occurs when moisture circulates in the system. It gets there either due to poor-quality evacuation during previous repairs, or due to the use of low-quality freon. Water freezes at temperatures below 0°C, blocking the thin channel of the capillary.
Removing the blockage and replacing the filter
If the diagnostics are confirmed, the only correct solution is to replace the filter drier and purge the entire system. Simply “breaking through” the blockage with pressure is often not enough, since dirt can remain in the bends of the evaporator and, after a while, will collect again into a plug.
The restoration procedure includes cutting off the old filter, installing a new one that matches the model of the refrigerator (for example, Danfoss or Carel), and thorough vacuuming for 30-40 minutes. Only after creating a deep vacuum is the system charged with freon.
In rare cases, when the blockage is localized at the very beginning of the capillary, craftsmen use the method of “piercing” or replacing the inlet section of the tube. However, this requires high qualifications and the availability of equipment for joining copper tubes of different diameters.
FAQ: Frequently asked questions
Is it possible to clean the capillary tube without nitrogen?
Theoretically, you can try using compressed air, but this is risky. The air contains moisture, which will make the problem worse by creating an ice jam. In addition, the pressure of household compressors (up to 8 atm) may be insufficient to remove dense mechanical blockages. It is better to contact a service center where nitrogen is available.
How much does it cost to replace a capillary tube?
The cost consists of the price of materials (copper tube, filter, freon) and the complexity of the work. If foaming of the housing is required to gain access to the evaporator, the price will be significantly higher than simply replacing the filter in an accessible area.
Why did the refrigerator stop freezing again after replacing the filter?
Perhaps there is moisture left in the system that was not removed by the vacuum pump, or the blockage has formed deeper in the evaporator. Also, the reason may be an insufficient amount of refilled freon or its poor quality.
How to prevent capillary clogging in the future?
The main prevention is to avoid long periods of idle time for the refrigerator in an unheated room and to carry out any repairs efficiently with mandatory vacuuming. The use of original filter-driers also extends the life of the system.