Reduced cooling efficiency or complete absence of cold in chamber often indicates a refrigerant leak. Owners old Soviet refrigerators and technicians of the 90s regularly face this problem, since the life of seals and tubes is not endless. Many try to solve the problem on their own, but the process requires not only tools, but also a deep understanding of the physics of the processes.
Before taking active action, you need to make sure that the problem lies precisely in a lack of gas, and not in a malfunction of the compressor or thermostat. System tightness is the first thing that is violated over time. If you notice oily stains on the tubes or a characteristic whistle during operation, the likelihood of a leak is high. However, without a pressure gauge station and a vacuum pump, it is impossible to accurately diagnose the condition of the circuit.
Self-filling is a complex technical process associated with risks to health and equipment. Freon is under pressure, and upon contact with an open flame it forms toxic compounds. In this article we will analyze the theoretical part and the sequence of actions so that you understand the scope of work, but remember: professional repair often saves more resources than handicraft experiments.
Diagnostics of leaks and preparation of equipment
The first stage is always finding a place depressurization. A visual inspection may not yield results if the microcrack is hidden by thermal insulation or is located in the foamed part of the housing. Use a soapy solution to check connections, but be careful with electrical components. If bubbles do not appear and there is no cold, the gas has probably escaped through an inconspicuous hole.
To carry out the work, you will need a specialized set of tools, which everyone rarely has lying around in the garage. Without vacuum pump and pressure station it is pointless to start work, since air and moisture will remain in the system, which will lead to blockage of the capillary tube. You also need a cylinder with the appropriate type of freon indicated on the unit nameplate.
⚠️ Attention: Never mix different types of refrigerants. Refilling R134a into a system designed for R12, without changing the oil and flushing the circuit, is guaranteed to cause the compressor to fail within a few hours.
Preparation of the workplace also plays a critical role. Ensure the room is well ventilated, as freon is heavier than air and can displace oxygen in the lower part of the room. Prepare tools for soldering if you need to replace the filter drier or repair pipes.
Necessary tools and materials
The quality of work directly depends on the equipment used. Cheap Chinese pressure gauges often lie, which leads to the wrong amount of gas filled. To work with old equipment it is better to use proven mechanical stations, since the electronics can malfunction due to interference.
You will need an accurate scale to weigh the cylinder, since refilling by weight is the most accurate method for household refrigerators. The pressure in the system is a variable value and depends on the ambient temperature, so you cannot rely only on the pressure gauge needle. You will also need a torch with solder and flux to seal the system after the intervention.
The list of required tools includes:
- 🛠️ Pressure gauge station with a set of hoses (blue for low pressure, red for high).
- 💨 Vacuum pump to remove air and moisture from the circuit.
- ⚖️ Electronic scales with an accuracy of 1 gram.
- 🔥 Gas burner and solder for copper pipes.
- 🧪 Cylinder with R12 or R134a freon (depending on the model).
Pay special attention to the filter drier. In case of any depressurization of the system, it absorbs moisture from the air and ceases to perform its function. Replacing the filter Required for any opening of the circuit, otherwise the moisture will freeze in the capillary tube and block circulation.
The process of vacuuming the system
After eliminating visible leaks and replacing the filter-drier, it is necessary to remove all air from the system. The oxygen remaining inside reacts with the compressor oil, forming acid, which corrodes the electric motor windings from the inside. Therefore, the stage vacuuming cannot be skipped or shortened in time.
Connect the hose from the vacuum pump to the service fitting or soldered tube. Turn on the pump and watch the needle on the low pressure gauge. It should go into the minus zone (usually up to -1 Bar or 30 inHg). The operating time of the pump depends on the volume of the system, but for old refrigerators it is at least 30-40 minutes.
It is important to control the process so that oil from the pump does not enter the refrigerator circuit. There are special traps or valves for this. If you are using a simple pump without protection, monitor the oil level in its inspection window.
☑️ Evacuation checklist
After achieving the required vacuum, close the valve at the station and only then turn off the pump. This will prevent oil from flowing back. Leave the system under vacuum for 15-20 minutes to monitor. If the pressure gauge needle begins to creep up, it means that the seal has been broken and a microcrack remains somewhere.
Refrigerant charging technology
Freon charging is the most critical stage. The amount of gas is strictly regulated by the manufacturer and indicated on the factory tag (usually from 60 to 140 grams for single-chamber models). Before starting work, the freon cylinder must be weighed and the readings recorded.
Open the valve on the cylinder and let gas into the system. Refueling is carried out with the compressor turned off until the pressure in the system and the cylinder are equalized. After this, you can briefly turn on the compressor for better gas distribution, but watch the pressure on the pressure gauge.
The process is controlled by scales:
- Subtract the weight of the required filling from the initial weight of the cylinder.
- Follow the scale readings during the gas supply process.
- As soon as the weight has decreased by the required value, close the valve.
Some masters use the charging method by current or temperature, but for old refrigerators with a fixed choke (capillary tube), the weighing method is the only correct one. The pressure in such systems may “float” and will not be informative without experience.
Why can’t you refill “by eye”?
Recharging with freon leads to liquid refrigerant entering the compressor, causing water hammer and destruction of the valves. Under-refueling leads to engine overheating and insufficient cooling.
Pressure control indicators
Although we have already said that pressure is not the main parameter, knowing its values is necessary for an initial assessment. The table below is for reference values at an ambient temperature of +25°C. Remember that for different types of freon the numbers will be different.
Measurements are taken at the suction pipe of the compressor. If the values differ greatly from the table, this may indicate a compression problem or a clogged system.
| Refrigerant type | Suction pressure (Bar) | Discharge pressure (Bar) | Temperature boiling |
|---|---|---|---|
| R12 (Freon-12) | 0.08 - 0.12 | 8.5 - 10.0 | -29.8°C |
| R134a | 0.05 - 0.08 | 9.0 - 11.0 | -26.1°C |
| R600a (Isobutane) | 0.04 - 0.06 | 5.0 - 7.0 | -11.5°C |
| R22 (Rarely in everyday life) | 0.40 - 0.50 | 14.0 - 16.0 | -40.8°C |
Please note that freon R600a, which is often found in later models, is explosive. Working with it in residential areas without a spark-proof tool is strictly prohibited. For older refrigerators, R12 and R134a are more common.
Sealing the system and final check
After successful filling, it is necessary to seal the system. To do this, bend the service tube with pliers a few centimeters from the compressor housing and seal it with a torch. This must be done quickly to minimize the release of gas.
Be sure to check the soldering area with soapy water for bubbles. Even a microscopic leak will ruin all your work in a few months. After the solder has cooled, wipe the flux off the tube, as it can cause corrosion.
⚠️ Attention: Do not use aluminum solder to join copper tubes without special activating fluxes. The quality of such a connection in the vibration environment of the refrigerator will be low.
Turn on the refrigerator and let it work for several hours. Check the uniform cooling of the evaporator and the temperature in the chamber. If all parameters are normal, the repair can be considered complete.
Common mistakes when doing DIY repairs
One of the most common mistakes is ignoring the replacement of the filter drier. Saving on this part leads to the formation of an ice plug in the capillary tube, which requires re-opening the system.
Another mistake is refilling “by eye” or by the operating time of the compressor. In older refrigerators with a modified evaporator geometry or after defrosting, the volume of the system may differ slightly, but the reference should be strictly on the scale. They also often forget to evacuate the system for a sufficient time, leaving moisture inside.
Some craftsmen try to use automotive freons with added oils or dyes. This cannot be done, since the chemical composition may not meet the requirements refrigerator compressor, which will lead to its rapid wear.
Is it possible to fill a refrigerator with freon from a lighter can?
No, it is not possible. Lighters use purified butane or a propane-butane mixture, which have different thermodynamic properties and can be explosive in concentrations with air if leaked. In addition, they do not contain the necessary additives for compressor lubrication.
How much does it cost to fill a refrigerator with freon in a workshop?
The price depends on the region and type of refrigerant, but usually consists of the cost of travel, labor and materials. Independent purchase of equipment (pump, station, cylinder) will pay off only after 3-4 refills.
Why does the refrigerator freeze only at the top after refilling?
This is a sign of a clogged capillary tube or the presence of an air lock. Most likely, during refueling, moisture or air got into the system and froze in a narrow place in the throttle. Repeated purging and vacuuming are required.