If your refrigerator suddenly stops freezing, and the compressor continues to hum without interruption, most likely there is a blockage in the refrigerant circulation system. The capillary tube is the thinnest channel responsible for throttling and supplying freon to the evaporator, and it is this tube that most often suffers from moisture or debris. Unlike large lines, the diameter of this element is a fraction of a millimeter, so even a microscopic particle of oxide or ice can completely stop the operation of the unit. Diagnostics such a malfunction requires attention, since the symptoms may resemble a gas leak or a compressor breakdown.
Before proceeding complex manipulations, it is important to understand the principle of operation of the system. The refrigerant under pressure moves along the circuit, passing through a narrow hole capillarywhere it expands sharply and cools. If the patency is impaired, the pressure at the entrance to the tube increases and at the outlet drops to zero, which blocks heat exchange. Independent cleaning is possible, but requires specific equipment and strict adherence to safety precautions, since the system is under pressure and contains chemicals.
In this article we will analyze in detail the algorithm of actions that will allow you to determine the localization of the plug and try restore the functionality of the refrigerator. We will look at methods of mechanical action, chemical washing and nitrogen purging, and also point out typical mistakes that inexperienced craftsmen make. Remember that any work with freons and soldering of copper tubes requires caution.
Diagnostics of a blockage: symptoms and signs
The first step in any repair is the correct diagnosis. A clogged capillary tube is often confused with a Freon leak, but there are key differences. When clogged, the compressor works almost non-stop, trying to gain temperature, but there is no cold in the chambers. In this case, the motor-compressor itself may heat up more than usual due to the increased load. If you touch the condenser grille at the back of the refrigerator, it will be either barely warm or cold, while in normal mode it should be uniformly hot.
The second important sign is the nature of the sounds. When a working refrigerator is operating, you can hear a uniform bubbling or hissing of freon passing through the capillary. If the system is clogged, these sounds disappear or become intermittent. Sometimes you can hear the compressor trying to start, humming for a few seconds and clicking, going into protection, although this is more often characteristic of problems with the start relay or the motor itself. In the case of capillary blockagethe motor most often hums continuously.
It is also worth paying attention to the evaporator inside the freezer. If you defrost the refrigerator, remove the ice, turn it on, and after a couple of hours one part of the evaporator is covered with frost, while the other (usually closer to the tube exit) remains clean and warm - this is a sure sign of an obstruction. Freon simply does not reach the end of the circuit. To accurately determine the location of the plug, professionals use a thermal imager or simply tactilely check the temperature of the tubes at the inlet and outlet of the filter-drier.
⚠️ Attention: If, after long-term operation of the compressor, the filter-drier remains cold and the condenser is hot, the blockage is located in front of the filter or in the filter itself. If the filter is hot and the evaporator is cold, the problem is in the capillary tube or after it.
Necessary tools and preparation for repair
Repairing a refrigeration circuit is not just replacing a part, it is working with a sealed system that requires vacuuming and refilling. In order to clean capillary tubeyou will need a specialized set of tools, which are usually available to professional craftsmen, but can also be assembled by an enthusiast. Without the proper equipment, an attempt at repair may lead to permanent failure of the unit.
First of all, access to the technical unit of the compressor is necessary. To do this, you will need a torch (gas or oxygen-propylene), solder (silver or copper-phosphorus) and flux. It is important to use refractory solders, since ordinary tin solder will not withstand the pressure and vibrations in the system. It is also critically important to have a cylinder with dry nitrogen for purging the system - this is key element high-quality cleaning.
The list of necessary equipment and materials includes:
- 🛠️ Vacuum pump and pressure gauge station for creating a vacuum and controlling pressure.
- 🔥 Gas torch with a set of solder and flux for soldering copper connections.
- 💨 Cylinder with dry nitrogen and a reducer for purging the circuit under pressure.
- 🧪 Solvent (for example, R141b or isopropyl alcohol) for chemical washing.
- 🔧 Set of pipe cutters, rolling pins and pliers for working with copper tubes.
Don't forget about personal protective equipment. Working with open flames and chemicals requires gloves, goggles and good ventilation. Refrigerants released during depressurization can be hazardous to health, and flux vapors during soldering are toxic. Before starting work, the refrigerator must de-energize be moved away from the wall, providing access from all sides.
Mechanical cleaning method and purging with nitrogen
The most effective way to remove blockages is considered to be purging the system with nitrogen under high pressure. This method allows you to knock out a plug from a narrow channel of a capillary using physical force. However, simply supplying gas to the system is not enough: you need to properly prepare the circuit and follow the sequence of actions so as not to damage other components.
The process begins by disconnecting the compressor from the system. The sealed tube at the suction is cut through, and a fitting from a pressure gauge station or a hose from a nitrogen cylinder is inserted into the hole. The system pressure must be relieved. Then the filter drier is sealed off from the condenser side. This is an important point, since in any case the old filter will have to be replaced with a new one after all cleaning work is completed.
Then follows the purging process itself:
- Apply nitrogen to the capillary tube from the condenser side (where the filter was). The pressure should be high, up to 10-15 atmospheres, but make sure that the tube does not break.
- If air flows freely and comes out with noise on the other side (from the evaporator side), it means that the capillary is clean and there was a blockage in the filter.
- If purging is impossible, try applying nitrogen in the opposite direction - from the evaporator side. Sometimes this helps to break through the oil plug.
- In particularly difficult cases, use the “water hammer” method, briefly increasing the pressure, but this is risky and can lead to rupture of the thin evaporator tubes.
⚠️ Attention: Never try to clean the capillary tube by blowing with your mouth or using a car compressor. The pressure of 8-10 atmospheres created by these methods is not enough to break through a serious blockage, and trapped moisture will only aggravate the situation by turning into ice during operation.
☑️ Check before soldering
If nitrogen passes through, but weakly, you can combine purge with chemical washing. A special solvent is poured into the tube, left for a while, and then purged with nitrogen again. The solvent softens oily deposits and wax plugs, allowing the gas flow to carry away their remains. After successful purging, the system is ready for assembly, but requires mandatory replacement of the filter.
Chemical washing and use of solvents
The chemical method is often used as an auxiliary method or when mechanical purging does not give a complete result. The main purpose of chemical washing is to dissolve organic deposits, oil oxidation products and wax that may have precipitated due to moisture ingress. For these purposes, special liquids are used, such as R141b, freon R22 (in the liquid phase) or high-quality isopropyl alcohol.
Rinsing technology consists of filling the circuit with a solvent. The liquid is poured into the capillary tube and left for several hours (sometimes for a day) so that the active substance dissolves the plug. Periodically, the tube can be slightly warmed with a hairdryer, but not with open fire, to speed up the reaction. After exposure, the solvent is drained and a thorough nitrogen purge is carried out to remove chemical residues and dissolved dirt.
It is important to understand that the use of aggressive chemicals requires caution. Some solvents can damage rubber seals or varnish insulation of compressor windings if they get there in large quantities. Therefore, it is better to perform flushing with a disconnected capillary tube or with a guarantee that liquid will not enter the compressor housing.
A comparison of cleaning methods is presented in the table below:
| Method | Efficiency | Complexity | Risks |
|---|---|---|---|
| Nitrogen purging | High | Medium | Tube rupture at high pressure |
| Chem. washing | Medium | Low | Damage to seals, residual moisture |
| Mechanical cleaning (string) | Low | High | Puncture of the tube from the inside, tool stuck |
| Replacement of the capillary | Maximum | High | Error in the length/diameter of the new tube |
Can WD-40 be used?
Using WD-40 to flush the refrigeration circuit is strictly prohibited. This liquid contains oils and components that, if they enter the system, will freeze or form new deposits, finally killing the refrigerator.
Replacing the filter-drier and vacuuming
Any operation to depressurize the circuit, including cleaning the capillary, requires a mandatory replacement of the filter-drier. This element is responsible for removing moisture from the system and retaining mechanical particles. An old filter that has been in the open air or simply worked for a long time will already be saturated with moisture and will not be able to perform its functions. Installing an old filter will negate all cleaning efforts.
The filter drier is selected strictly according to the brand of refrigerant and the compressor power of your refrigerator. There is always a marking on the case, for example Danfoss DCR-48 or analogues. When soldering a new filter, it is important not to overheat its housing, since there is a zeolite filler inside, which can lose its properties at temperatures above 100-120°C. You need to solder quickly and carefully, using a damp rag to cool the filter housing.
After installing all components, the vacuum stage begins. This is a critical process to remove air and moisture vapor from the system. The air contains oxygen, which oxidizes the oil, and water, which freezes in the capillary, forming an ice plug. The vacuum pump is connected through the service valve and operates from 30 minutes to several hours, depending on the power of the pump and the volume of the system.
The vacuuming process looks like this:
- 🔌 Connect the vacuum pump to the service port (usually in place of the sealed tube).
- 📉 Enable pump and watch the pressure gauge needle, which should go into the green zone (vacuum).
- ⏳ Leave the pump running for at least 30-40 minutes for the moisture to completely boil away.
- 🔒 Close the valve, turn off the pump and watch the arrow for 15-20 minutes. If the arrow does not rise, the system is sealed.
⚠️ Attention: If, after turning off the pump, the pressure in the system begins to increase, it means that there is a leak somewhere (microcrack, poor soldering). You cannot continue charging - you need to look for and fix the leak, otherwise the refrigerator will stop freezing again after a short time.
Refrigerant charging and final check
The last stage of repair is charging the system with refrigerant. The type and amount of gas is indicated on the label located on the back wall of the refrigerator or inside the chamber. Most often, household refrigerators use R134a or R600a (isobutane). Refilling with isobutane requires special care, since this gas is explosive when concentrated in air, and all work should be carried out in a well-ventilated area away from fire sources.
Refilling is carried out with the compressor running through the service valve, monitoring the pressure using a pressure gauge and the current consumption of the compressor using an ammeter. The suction pressure must correspond to the boiling point of the refrigerant. For example, for R134a during normal operation it is about 0.1-0.2 bar (excessive), but the exact values depend on the temperature in the chamber. Overfilling is just as harmful as underfilling: excess gas can lead to water hammer and compressor breakdown.
After filling, the capillary tube is sealed. To do this, clamp the filling tube with clamping pliers a few millimeters from the edge, cut above the clamp and quickly seal the hole with a torch. Then check the operation of the refrigerator for several hours. The evaporator should be covered with a uniform layer of frost, and the temperature in the chambers should begin to decrease.
If after all the procedures the refrigerator began to freeze, but after a few days the problem returned, it means that the blockage was not completely eliminated or moisture remained in the system. In such cases, a repeated procedure with a longer vacuum and heating the tubes with a hairdryer to evaporate moisture often helps. Sometimes it is necessary to completely replace the capillary tube with a new one, selected in length and internal diameter.
Frequently asked questions (FAQ)
Is it possible to clean a capillary tube without nitrogen?
Theoretically, you can try using a compressor or even a compressed air cylinder, but the effectiveness of this method is extremely low. A pressure of 8 atmospheres is often not enough to break through a dense oil-paraffin plug. In addition, ordinary air contains moisture, which, if it enters the system, will freeze and create a new, even more complex blockage. Nitrogen is used because it is dry and inert.
Why can’t you just blow out the system with your mouth?
A person is not able to create a pressure above 0.5-0.8 atmospheres, while cleaning a capillary requires a minimum of 10-15 atmospheres. In addition, the exhaled air is saturated with water vapor. The entry of even a microscopic amount of moisture into the freon circuit will lead to the formation of an ice plug in the capillary at operating temperature, and the refrigerator will stop freezing immediately after switching on.
How to understand that it is the capillary that is clogged and not the filter?
When the filter-drier is clogged, the filter housing is usually cold or covered with frost, as throttling occurs inside it. When the capillary tube is clogged, the filter remains warm (since there is high pressure in front of it), and the section of the tube after the plug becomes cold. An accurate diagnosis can only be made by measuring the temperature along the length of the circuit or opening the system.
Do I need to flush the system if I change the compressor?
If the old compressor burned out, releasing combustion products and acid into the system, flushing is required. If the compressor is changed for other reasons (mechanical knock, wedge), and the oil in the system is clean, it is enough to replace the filter drier and perform a vacuum. Flushing is only necessary if there is visible dirt or suspected moisture.