A sudden breakdown of the cooling system in the refrigerator often becomes an unpleasant surprise that disrupts the usual way of life. When food stops freezing and the main chamber becomes too warm, the first thing that comes to mind is calling a specialist, but many problems can be fixed on your own. One of the most common causes of such problems is the failure or incorrect operation of the thermostat, especially the popular series K-59.
Thermostat K-59 is a mechanical device that controls turning the compressor on and off based on temperature sensor readings. This sensor is mounted on the evaporator of the refrigeration chamber, and it is its incorrect readings that often lead to the fact that the refrigerator either does not turn off at all or operates in too short cycles. Understanding the operating principle of this unit will allow you not only to save on the services of a service center, but also to extend the life of the equipment.
In this article we will analyze in detail the process of diagnostics, dismantling and, most importantly, correct adjustment of the thermostat. We will look at typical mistakes that beginners make and give practical advice on setting temperature conditions.
The operating principle and design of the thermostat
The series thermostat K-59 refers to a mechanical type of device, where the main working element is a bellows tube filled with a temperature-sensitive gas (usually freon). When the temperature in the refrigeration chamber evaporator changes, the gas expands or contracts, affecting the bellows membrane. This mechanical movement is transmitted to a group of contacts, closing or opening the electrical circuit of the compressor.
The design of the device is quite simple, but requires precise adjustment for correct operation. Inside the case there is a spring mechanism that can be adjusted using screws. Setting the K-59 is produced by changing the spring tension, which affects the contact threshold. Typically, there are two adjusting screws on the thermostat rod: one is responsible for the temperature range, and the second is for the differential value (the difference between the on and off temperatures).
Technical features of the K-59 series
Unlike electronic sensors, mechanical thermostats of the K-59 series do not require external power and are controlled solely by the physical properties of the gas in the bellows. Their reliability has been tested for decades, but over time, the springs can lose elasticity and the contacts can burn, which requires intervention.
It is important to understand that the thermostat does not directly measure the air temperature in the chamber; it reacts to the temperature of the evaporator tube to which its capillary tube is attached. That is why fastening accuracy and thermal conductivity of the contact point play a decisive role in the final temperature inside the refrigerator. If the contact is broken, the readings will be incorrect and the products may deteriorate.
Fault symptoms and diagnostics
Before you start making adjustments, you need to make sure that the problem lies in the thermostat and not in other components of the refrigerator. There are a number of characteristic signs indicating a malfunction of the thermostat K-59. Ignoring these symptoms can lead to more serious breakdowns, for example, failure of the compressor due to non-stop operation.
- ❄️ The refrigerator has stopped turning off and is working around the clock, while a “fur coat” forms in the freezer, and in the main chamber the temperature can be either normal or excessive low.
- 🌡️ The compressor turns on very rarely or does not turn on at all, the temperature in the chambers rises, the food begins to deteriorate, although the light is on.
- ⚡ When you turn the temperature adjustment knob, a characteristic click is heard, but the compressor does not respond, or, conversely, there is no click at all.
- 💧 There is no or, conversely, an excessive amount of ice on the back wall of the refrigerator compartment, which indicates incorrect operating cycles.
For an accurate diagnosis, experts recommend conducting a simple test. If the refrigerator does not turn off, try forcibly unplugging it for 15-20 minutes and then turning it on again. If, after turning on, it worked for the standard time (20-40 minutes) and turned off, the contacts may have stuck, which was eliminated after cooling. However, if the situation repeats, intervention is required.
It is also worth checking the integrity of the capillary tube. If it is kinked or damaged, gas could escape and the thermostat will physically not be able to work. Visual inspection often allows you to identify obvious defects without the use of complex equipment. Checking the contacts a multimeter will also give an unambiguous answer: in a cold state (if the sensor is removed from the chamber), the contacts should be closed, and when heated, they should open.
Preparation for adjustment and dismantling
Adjusting the thermostat K-59 is impossible without first dismantling it, since the adjusting screws are usually hidden under a seal or are located in a hard-to-reach place inside the housing. The removal process requires care so as not to damage fragile plastic elements and wire insulation.
☑️ Preparation for dismantling the thermostat
First you need to get to the installation site thermostat. In most refrigerator models where it is used K-59, it is located inside the refrigerator compartment in a plastic case or behind the control panel. Remove the temperature control knob, unscrew the mounting screws and carefully remove the device body. Be careful with the capillary tube - it is very thin and breaks easily.
After removing the housing, disconnect the wires from the thermostat terminals. Before doing this, be sure to make sure that the refrigerator is unplugged. Remember or write down which wire is connected where, as the diagram may vary depending on the manufacturer of the refrigerator. Usually the wires are marked with colors or numbers, but double-checking will not be superfluous.
⚠️ Attention: The capillary tube of the thermostat is filled with refrigerant under pressure. Never bite or bend it sharply to avoid causing a gas leak, which can be dangerous if inhaled in a confined space.
When the thermostat is removed, inspect it for external damage. If the housing is cracked or burn marks are visible on the contacts, adjustment may not help and a complete replacement of the assembly will be required. However, if the device looks intact on the outside, you can try to adjust it.
K-59 thermostat adjustment technology
The process of adjusting the thermostat K-59 consists in changing the tension of the internal spring. There are usually two screws located on the device stem that extends from the housing. One screw (often larger or deeper) is responsible for the contact opening temperature, that is, at what temperature the compressor will turn off. The second screw adjusts the differential - the temperature difference between turning on and off.
To make the adjustment you will need a small screwdriver. Turning the screw clockwise will generally increase spring tension, which will result in lower shutdown temperatures (the refrigerator will be colder). Counterclockwise rotation weakens the spring, increasing the shutdown temperature.
It is important to make adjustments in small steps, turning the screw no more than half a turn or even less. After each manipulation, it is necessary to assemble the refrigerator, turn it on and let it run for several hours to stabilize the temperature. Only after this can measurements and conclusions be made.
| Action | Rotation direction | Result | Risk |
|---|---|---|---|
| Increased cooling | Clockwise | The compressor turns off at a lower temperature | Freezing food, non-stop operation |
| Reducing cooling | Counterclockwise | The compressor turns off at a higher temperature temperature | Insufficient cooling, spoilage of food |
| Increasing the differential | Adjusting the 2nd screw | More rare but longer operating cycles | Larger temperature fluctuations |
| Reducing the differential | Adjusting the 2nd screw | Frequent switching on and off | Wear of the compressor |
You should not try to adjust the thermostat “by eye” without temperature control. The ideal option is to use an external thermometer placed in a glass of water in the central part of the refrigerator compartment. This will allow you to obtain objective data about the real temperature inside.
Setting the temperature and monitoring indicators
After the mechanical adjustment of the screws, the control stage begins. Correct temperature in the refrigerator should be in the range from +2 to +6 degrees Celsius in the main chamber. In the freezer, the temperature should drop to -18 degrees or lower. The thermostat K-59 first of all controls the temperature of the evaporator, therefore it indirectly affects the overall climate.
To check, place a regular household thermometer in a container of water and place it on the middle shelf of the refrigerator chambers, away from the walls. Leave the refrigerator operating normally for at least 4-6 hours. Then take your readings. If the temperature does not correspond to the desired one, the screw adjustment procedure will have to be repeated.
⚠️ Attention: Do not adjust the thermostat if the refrigerator has just been defrosted or a large batch of warm food has been loaded into it. Allow the equipment to return to operating mode for 24 hours before making changes.
Pay attention to the duration of the operating cycles. A normal mode is considered when the compressor works about 30-40% of the time (for example, it works for 15 minutes, rests for 30 minutes). If, after adjustment, the refrigerator starts to turn on too often (every 2-3 minutes), this indicates that the differential is too small, which is harmful for the engine.
Typical mistakes and precautions
When independently adjusting the thermostat K-59 home craftsmen often make mistakes that can lead to aggravation of the situation. The most common of these is over-tightening the adjustment screw in the hope of “making it colder.” This often leads to the fact that the refrigerator stops turning off altogether, which is fraught with freezing of the evaporator and overheating of the compressor.
Another mistake is ignoring the condition of the door seal. If the door does not close tightly, no thermostat will be able to maintain a normal temperature, and the compressor will wear out. Before adjustment, make sure that sealing rubber is intact and fits tightly around the entire perimeter.
- 🔧 Attempting to adjust without disconnecting the device from the network - there is a risk of electric shock.
- 🌡️ Evaluation temperature by touch or by condensation instead of using a thermometer.
- 🔩 Rotating the adjusting screws too sharply, which can lead to thread breakage or breakage of the mechanism.
- 🧊 Forgetfulness in returning the capillary tube to its place - it must fit tightly to the evaporator.
It is also worth remembering that the resource of a mechanical thermostat is limited. If your refrigerator is more than 10-15 years old, adjustments can only give a temporary effect. In this case, it is more rational to replace the unit with a new one, similar K-59 or its modern imported analogue.
Is it possible to use a thermostat from another model?
In some cases it is possible to install analogues (for example, TAM-133), but they may have different capillary tube length and response characteristics. This will require additional complex setup and does not always guarantee stable operation. It is better to use the original or a complete analogue.
How often should you change the thermostat in the refrigerator?
The average service life of a mechanical thermostat is 7-10 years. However, with intensive use or power surges, it may fail earlier. If you notice that the adjustment stops producing results, or the contacts burn out, it’s time for a replacement.
Why does the refrigerator not turn off after replacing the thermostat?
Perhaps the new thermostat has different factory settings or a defect. Also, the reason may be incorrect installation of the capillary tube (poor contact with the evaporator) or a lack of freon in the system, due to which the evaporator does not cool to the required temperature.
Is it possible to repair the K-59 thermostat yourself?
Full repair (replacing the bellows, membrane) at home impossible and impractical. Repair usually means only external adjustment of screws or cleaning of contacts, if access is available. In most cases, it is easier to replace a faulty unit.
What to do if the adjusting screw spins endlessly?
If the screw does not have a stop and spins freely, the thread may be broken or the mechanism inside is destroyed. In this case, adjustment is impossible, and the thermostat must be replaced with a new one.