Owners of Soviet and post-Soviet refrigeration equipment are often faced with the need to manually adjust the climate inside the chambers. Unlike modern models with electronic control, where all parameters are set by pressing buttons on the display, old refrigerators require mechanical intervention and understanding of the principles of operation of the thermostat. Incorrect settings can lead to food spoilage or excessive energy consumption.
The main difficulty is that the control mechanism in units such as ZIL, Biryusa or early models Indesitis often hidden behind decorative panels or made in the form of a rotary knob without digital scale. To effectively control the temperature regime, it is necessary to accurately determine the location of the thermostat and understand the logic of its operation. In this article, we will look at all the nuances of setting up so that your refrigerator works in optimal mode.
Understanding how it works thermostatwill help you avoid common mistakes. In older models, it is an electromechanical device that opens and closes the electrical circuit of the compressor depending on the temperature in the evaporator. The accuracy of such a system is lower than that of digital analogues, so the setting process requires patience and control using an external thermometer.
The principle of operation of a mechanical thermostat
The temperature control system is based on thermostat (thermostat). This device responds to changes in temperature inside the refrigerator compartment or on the surface of the evaporator. Structurally, it consists of a bellows (sealed corrugated container) filled with refrigerant and a contact group. When the temperature rises, the gas in the bellows expands, presses on the membrane and closes the contacts, starting the compressor.
When the chamber cools to the set value, the reverse process occurs: the gas pressure drops, the spring opens the contacts, and the engine stops. In older models, such as Saratov or Minsk, adjustment is carried out by changing the spring tension. This is done either by turning the knob on the panel, or by tightening the screw inside the device body. It is critically important to understand that a mechanical thermostat does not directly regulate the air temperature in the chamber, but the compressor shutdown temperature.
It is worth noting that In two-compartment models with one compressor, the thermostat is usually installed in the refrigerator compartment. The freezer compartment is cooled according to the residual principle, so when adjusting, you need to focus on the average temperature of the main compartment. If you set the thermostat too “cold,” the food in the freezer may freeze, and the compressor will work without interruption.
How does a capillary tube work?
The heat-sensitive element (capillary tube) can be installed inside the chamber (the end of the tube is visible) or built into the wall of the evaporator. In older models, there is often an option where the tube is simply pressed against the evaporator. When replacing or adjusting, it is important not to damage this tube, since freon leakage from the bellows will lead to the thermostat not working.
Where to find the regulator in older models
The location of the controls depends on the year of manufacture and the specific model of the refrigerator. In most older units, the regulator is located outside for user convenience. Usually this is a plastic pen with graduations from 1 to 5 or from "Min" to "Max". It may be located inside the refrigerator compartment on the side wall or on the ceiling, next to the lampshade.
However, in some cases, especially in refrigerators from the 70s and 80s, the regulator may be hidden. For example, in models ZIL-63 or KSh-57 access to the adjustment screw can only be achieved after removing the decorative trim or even dismantling the front panel. If you do not see an obvious knob with numbers, carefully inspect the interior: sometimes the regulator is hidden under the lampshade or behind the thermostat cover.
In two-compressor models (where each chamber has its own unit), the thermostats are located independently. The refrigerator compartment regulator is located inside it, and the freezer regulator is located inside the freezer. In systems such as Sviyaga or two-compressor Biryusa, each zone is configured independently, which simplifies the task of maintaining different temperature conditions.
Step-by-step instructions for setting the temperature
The adjustment process requires a sequence of actions, since the inertia of the system is large. After any change in the position of the handle or screw, you must wait time for the temperature to stabilize. First, prepare a household thermometer that can measure subzero temperatures and a glass of water to check whether the food has actually cooled.
If your refrigerator is equipped with a knob with divisions, set it to the middle position (usually number 3). If adjustment is made with a screw (a screwdriver is required), make no more than half a turn at a time. Write down your starting position so you can return to it if you fail. Then start the compressor and let the system run a full cycle.
After 6-8 hours, measure the temperature in the central part of the chamber, not at the walls. The normal range for food storage is +2...+5 °C. If the temperature is higher, it is necessary to increase the cooling (turn the knob to a higher number or tighten the screw clockwise). If food freezes slightly, lower the setting. Repeat the procedure until a stable result is achieved.
☑️ Algorithm for setting the thermostat
Table of correspondence between settings and temperatures
Since there are no degrees on the handles of old refrigerators, but only conventional units, you have to rely on approximate values. Below is a table that will help you navigate the approximate correspondence between the position of the regulator and the temperature inside the chamber for a working refrigerator.
| Handle position | Approximate temperature inside | Compressor operating mode | Recommendation |
|---|---|---|---|
| 1 (Min) | +7...+9 °C | Short cycles, a lot of downtime | Summer, storing vegetables |
| 3 (Avg.) | +3...+5 °C | Normal cycle (40/60) | Standard mode |
| 5 (Max) | 0...+2 °C | Long operation, little downtime | Winter, fast cooling |
| Above 5 | Lower 0 °C | Continuous operation | Risk of icing |
It is important to consider that these values are relevant for serviceable units with normal seals. If the door rubber has lost its elasticity and allows heat to pass through, the compressor will run longer even at minimum settings, trying to compensate for the heat gain. In this case, adjusting the thermostat will not solve the problem, but will only lead to its overload.
Seasonal adjustment and external factors
The ambient temperature directly affects the operation of the old refrigerator. In the summer, when the apartment is hot, the heat transfer of the condenser worsens and the compressor takes longer to cool. During this period, it is recommended to set the regulator to lower values (numbers 4-5) to compensate for the high heat gain.
In winter, the situation changes. If the refrigerator is in an unheated room or in the kitchen, where the temperature drops below +16 °C, the thermostat may simply not turn on. Older mechanical thermostats are often not designed to operate in cold climates: the gas in the bellows does not expand enough to close the contacts. In this case, the food may defrost, even if the handle is set to “Maximum”.
⚠️ Attention: Operating most old refrigerators at ambient temperatures below +10°C is prohibited by the instructions. The oil in the compressor thickens, lubrication deteriorates, which can lead to jamming of the mechanism. If use in the cold is necessary, installation of a special thermostat zone heater is required.
It is also worth considering the location of the refrigerator. If it is close to the stove, radiator or in direct sun, the sensor will read the increased temperature and keep the compressor on constantly. In such cases, adjusting the thermostat is useless - it is necessary to eliminate the heat source or rearrange the unit.
Diagnostics of thermostat malfunctions
Sometimes the adjustment does not produce results due to a breakdown of the thermostat itself. If the compressor does not turn on at all, even when the contacts are closed manually, or, conversely, it works non-stop and gets very cold, the device is likely to malfunction. In older models, the contacts could simply be burned or stuck.
You can check the functionality by temporarily removing the thermostat from the circuit (short-circuiting the wires directly). If the refrigerator starts working and starts freezing, the problem is in the regulator. If the compressor hums but does not start, or clicks, the problem may be in the start relay or the motor itself. It is also worth checking the capillary tube: if it is damaged or disconnected from the evaporator, the thermostat will not sense the real temperature.
Replacing the thermostat in old refrigerators is a procedure accessible to a home handyman. The main thing is to choose an analogue with similar characteristics (on/off temperature and capillary length). After installing a new device, you will definitely need to readjust it in the manner described above.
⚠️ Attention: Before any work on the electrical part of the refrigerator, be sure to disconnect it from the network! 220V voltage is dangerous to life. Check the contacts only with the device de-energized, using a multimeter in continuity mode.
What to do if the knob scrolls?
If the regulator knob scrolls 360 degrees without clicks or changes in resistance, most likely the rod inside the thermostat has broken. In this case, it is impossible to regulate the temperature by rotation - a complete replacement of the thermostat is required. Temporarily, you can try to carefully tighten the adjusting screw inside the case (if you have access), but this is a temporary solution.
Frequently asked questions (FAQ)
Why does the refrigerator freeze even at the minimum setting?
This may indicate sticking thermostat contacts or loss of bellows tightness (gas leak). It is also possible that the capillary tube is not properly secured and is not in contact with the evaporator, which is why the sensor does not “feel” the cold. Diagnostics and, probably, replacement of the thermostat are required.
Is it possible to replace a thermostat from one old refrigerator to another?
Yes, this is often possible if the geometric dimensions, capillary tube length and temperature range match. However, for accurate work, it is better to look for the original spare part number or a complete analogue, since different models may have different operation logics (for example, they are different for single-chamber and double-chamber refrigerators).
How often do you need to defrost an old refrigerator for the thermostat to work correctly?
Old models with manual defrosting require regular de-icing. The thick "coat" on the evaporator acts as a heat insulator, preventing the thermostat from reading the temperature correctly. Defrosting is recommended as ice builds up (usually once every 1-3 months), but at least twice a year for prevention.
Does the amount of food in the chamber affect the temperature setting?
Yes, a full chamber keeps the cold more stable and requires less intense compressor operation. An empty refrigerator will heat up faster when the door is opened, causing the thermostat to turn on the motor more often. When setting up for the first time after a long period of inactivity, it is better to load the chamber with food at least halfway.