Owners of Soviet equipment are often faced with the need to fine-tune operating modes, since automation in models of the last century required manual intervention. Old refrigerators Biryusa, produced in the 80s and 90s, are reliable, but their thermostats can lose settings over time or work incorrectly due to wear and tear. Understanding the principle of operation of the mechanical regulator will allow you to return the unit to the optimal cooling mode without calling a technician.
Before turning the knobs and checking the degrees, it is important to understand that in such models there is no electronic display showing the exact number. Thermostat here it works on the principle of closure and opening contacts when a certain temperature inside the chamber is reached. Your task is to experimentally find the position of the handle in which the food will not freeze at the back wall, and the door will remain cool.
In this article we will analyze the design of the mechanical control unit, consider typical malfunctions and give a step-by-step algorithm for achieving the ideal cold balance. You will learn how to distinguish a breakdown of the thermostat from a freon leak and when it is really time to replace the part.
Design of a mechanical thermostat in Biryusa models
The main element of climate control in old refrigerators Biryusa is a mechanical thermostat, often labeled as TAM-112, TAM-125 or similar indexes. Inside the housing is a bellows tube filled with freon gas, which reacts to changes in temperature in the evaporator. When heated, the gas expands, the pressure in the tube increases, and the membrane closes the electrical circuit, starting the compressor.
The regulator handle, located inside the refrigeration chamber or on the body, mechanically acts on the spring, changing the compression force. By turning the knob, you change the tension of the spring, which requires more or less expansion of the throttle to turn on the motor. This is exactly how it is set temperature rangein which your unit will operate.
It is important to note that in two-chamber models only the temperature in the refrigerator compartment is regulated, and the freezer compartment is cooled due to a pressure difference or a separate circuit. Therefore, the adjustment of the handle primarily affects the upper chamber, where ready-made dishes and drinks are stored.
⚠️ Attention: The thermal balloon (sensitive tube) in older models is often attached to the evaporator with a clamp. If it moves away or moves, the refrigerator will not work correctly, regardless of the position of the regulator knob.
The design of the thermostat implies the presence of a differential - the temperature difference between turning on and off the compressor. In old Biryusha this spread can be from 2 to 4 degrees Celsius, which is the norm for the mechanics of that time. You should not expect accuracy down to a tenth of a degree, as in modern inverter systems.
Deciphering the scale and operating modes
On the handle of the mechanical regulator there are usually numbers from 1 to 5, 6 or 7, or the designations “Min” and “Max”. Many users mistakenly believe that the number indicates degrees Celsius, but this is only a conventional scale of cooling power. The higher the number, the more compressed the spring inside the thermostat is, and the longer the compressor will work, lowering the temperature.
The position of the knob at the “1” or “Min” mark means that the compressor will turn on rarely and work for a short time. This is a mode for storing vegetables or when the refrigerator is almost empty. Setting it to “Max” or “7” forces the unit to work almost non-stop, which can lead to freezing products and the formation of an ice coat.
The optimal position for everyday use is considered to be the middle of the scale - usually numbers 3 or 4. This mode ensures a balance between the safety of products and energy consumption. If you load the chamber with a large amount of warm food, you can temporarily strengthen the mode, but then be sure to return the handle to its original position.
It is worth considering that the scale is not linear. Going from 1 to 2 can change the temperature by 2 degrees, and from 5 to 6 - only by half a degree, since the resources of the compressor and heat exchanger are not unlimited. In very hot summers, it makes sense to shift the regulator by 1 notch towards increased cold, compensating for the heating of the case from the environment.
Step-by-step instructions for adjusting the temperature
For correct settings, you will need a household thermometer, preferably with a probe that can be placed on a shelf. The calibration process takes time as the refrigerator needs to stabilize after each setting change. Do not try to turn the knob every 10 minutes - this will disrupt the compressor cycle.
First defrost the unit completely if there is ice on the walls. The ice crust acts as a heat insulator, and the thermostat will “think” that the chamber is warm, causing the motor to work in vain. After defrosting, load the chamber with food at least halfway, since the empty volume is cooled differently than the filled one.
☑️ Algorithm for setting the temperature
Put the thermometer on the middle shelf, away from the back wall and doors. Close the door and leave the refrigerator to operate as normal for 5-6 hours. During this time, the temperature will be established and you will be able to take readings. The ideal temperature for the refrigerator compartment is considered to be from +2 to +5 degrees Celsius.
If the thermometer shows above +5 degrees, turn the knob one notch towards an increasing number. If the temperature is below +2 or the food at the back wall is frozen, reduce the power by turning the knob towards a lower value. After each adjustment, wait for stabilization again for several hours.
⚠️ Attention: Never try to adjust the temperature by removing the thermostat outward or by touching its internal elements with a screwdriver. All settings are made only by turning the external knob.
The influence of the environment and load on work
Old refrigerators Biryusa are very sensitive to room temperature. If the kitchen is located on the sunny side or there is a stove nearby, heat exchange is disrupted. In such conditions, even the maximum setting of the regulator may not produce the required cold, since the condenser does not have time to release heat to the environment.
The loading density of the chambers also plays a critical role. A jam-packed refrigerator allows cold air to pass through worse, creating “heat pockets.” On the contrary, an almost empty unit loses cold instantly when the door is opened, and the compressor is forced to turn on more often. Try to keep the chamber filled at least 60-70%.
Seasonality is another factor. In winter, when the apartment is cool, the refrigerator may not turn on at all for a long time if the handle is set to minimum. In summer, with high humidity and air temperature, the same mode “1” can lead to food spoilage. Adjustment is a dynamic process that depends on the time of year.
Check the rubber seals on the doors. If they are dry and do not fit tightly, warm air will constantly be sucked in. In this case, no adjustment of the thermostat will help - the compressor will thresh without stopping, trying to compensate for the heat influx, and the temperature will still be high.
Typical faults and diagnostic methods
If adjusting the knob does not produce results, the thermostat itself may be faulty or a refrigerant leak has occurred. A characteristic sign of a breakdown of the thermostat is a situation when the compressor either does not turn on at all, or works continuously, without turning off even with strong cooling.
To check, you can carry out a simple test: with the refrigerator running, slowly turn the control knob from minimum to maximum. If you hear a characteristic click and the compressor reacts (turns on or off), then the electrical part is intact. Lack of response may indicate stuck contacts or an open circuit.
Freon leakage manifests itself differently: the refrigerator is humming, the compressor is hot, but there is no cold or it is very weak, and there is no uniform layer of frost on the evaporator (the back wall inside). In such cases, setting the temperature is useless - repair and refilling the system is required.
| Symptom | Probable cause | Action |
|---|---|---|
| The compressor does not turn on | Faulty thermostat | Part replacement |
| Continuous operation without shutdown | Freon leak or relay sticking | Master diagnostics |
| Foods freeze on minimum | Thermostat calibration failure | Adjustment or replacement |
| Temperature floats randomly | Poor contact or oxidation | Cleaning contacts |
Another common problem with old ones Biryus is the loss of tightness of the thermostat bellows. The gas evaporates and the membrane stops responding to temperature. In this case, only installing a new compatible thermostat will help, since these units usually cannot be repaired.
Care for the cooling system for stable operation
In order for the temperature settings to be maintained for a long time, it is necessary to monitor the cleanliness of the condenser (the grille at the back of the refrigerator). Dust and animal hair clog the cells, impairing heat transfer. Regular cleaning with a vacuum cleaner or a soft brush will extend the life of the compressor and make the thermostat more predictable.
Do not place the refrigerator close to the wall. For normal air circulation around the body, a gap of at least 5-10 centimeters is required. If the radiators heat themselves due to lack of ventilation, the cooling efficiency will drop, and the regulator will have to be turned to maximum, which leads to overload.
How to extend the life of an old thermostat?
Avoid abruptly switching the knob immediately from minimum to maximum. Move the position smoothly, giving the mechanism time to react. Also, do not allow moisture to get inside the regulator body when washing the refrigerator.
Monitor the condition of the drainage hole in the refrigerator compartment. If it is clogged, water will accumulate at the bottom, increasing the overall humidity and disrupting heat exchange. Cleaning the hole with a brush or a cotton swab is a simple procedure that improves the climate inside the chamber.
Why the Biryusa refrigerator does not maintain the temperature even at maximum?
Most likely, there is a refrigerant leak or the compressor has lost performance. It is also possible that the thermostat is completely out of order and does not give a signal to turn on, or the seal of the chamber is broken.
Is it possible to replace a mechanical thermostat with an electronic one?
Theoretically it is possible, but this requires a deep rework of the control system, changing the connection diagram and installing new sensors. For older models, it is more economically feasible to buy a new mechanical thermostat of the same series.
How often do you need to defrost an old refrigerator?
Models with manual defrosting require cleaning from ice when its layer reaches 3-5 mm. This usually happens once every 3-6 months, depending on the humidity in the room and the frequency of opening the door.
What does a crackling sound mean when you turn the control knob?
A slight crackling or clicking sound is normal, this is how the contacts close or open. If the sound is loud, like a crunch, the plastic mechanism for transmitting rotation to the shaft may have broken inside.