Has the refrigerator stopped coping with its tasks, are food starting to deteriorate or, conversely, turning into an icy monolith? In most cases, the cause of such problems is failure or incorrect calibration thermostat. Model K 59, manufactured by Danfoss (formerly Danfoss/Secop), is one of the most common mechanical temperature controllers installed in two-chamber refrigerators of various brands, including Indesit, Ariston, Beko and Stinol.
Understanding the operating principle of this device will help you not only carry out competent diagnostics, but and perform the adjustment yourself, avoiding calling a technician. Mechanical thermostat reacts to changes in temperature in the evaporator, opening and closing the electrical circuit of the compressor. If this process is disrupted, the entire cooling cycle is disrupted.
In this article we will analyze in detail the device of the K 59 thermostat, describe the sequence of actions for its precise adjustment and replacement. You will learn how to distinguish a sensor malfunction from problems with the refrigerant and what tools you will need for the job. Precise adjustment will extend the life of the compressor and ensure proper storage of products.
Design and principle of operation of the thermostat K 59
Thermoregulator K 59 is an electromechanical device that controls the operation of the compressor based on the readings of the temperature sensor. The main structural element is a bellows tube filled with a temperature-sensitive gas (freon). When the temperature in the fridge compartment changes, the gas pressure inside the tube changes, which leads to mechanical movement of the membrane and opening of the contacts.
Model K 59 has three terminals for connecting electrical wires, which distinguishes it from single-position analogues. One contact is responsible for the voltage input, the second for supplying power to the compressor, and the third for the operation indicator lamp or fan (depending on the refrigerator circuit). Understanding this circuit is critical for connection. diagnosis and connection.
Technical characteristics K 59
Operating temperature range is from -24°C to +3.5°C (on/off). The length of the capillary tube can vary from 0.5 to 2.5 meters depending on the modification (L-length). The contact force is designed to work with compressors up to 1/2 hp.
It is important to note that the adjusting screws are sealed and filled with paint at the factory. This is done in order to prevent unskilled intervention. However, during repairs it is often necessary to reset the factory settings or adapt the operation of the thermostat to specific operating conditions.
Required tools and safety measures
Before starting any work on the electrical equipment of the refrigerator, you must strictly follow the electrical safety rules. The very first action is to completely disconnect the appliance from the electrical network. Even a brief touch of exposed live wires can lead to serious injury.
- 🔧 Multimeter —necessary to check the continuity of the circuit and resistance of the thermostat contacts.
- 🪛 Set of screwdrivers —you will need Phillips and flat-head screwdrivers of different sizes to remove panels and casings.
- 🌡️ Thermometer —a household or professional device for monitoring the actual temperature inside the chamber.
- 🧤 Gloves —to protect hands from sharp metal edges and possible contact with the refrigerant if handled carelessly.
If you plan to not only replace, namely adjust the old thermostat, you may also need a small slotted screwdriver or a special wrench to turn the adjusting screws under the seal. Be prepared for the paint on the screws to crumble.
Diagnostics: when adjustment or replacement is needed
Before tightening the screws or buying a new part, you need to make sure that the problem lies in the thermostat. Symptoms of a malfunction may be similar to a freon leak or a compressor failure. If the refrigerator is “silent” and does not turn on at all, or, conversely, works non-stop, turning the chamber into a freezer, suspect first of all you should check the thermostat. To check, remove the thermostat and immerse its sensitive tube in a container with water at room temperature (about +20°C). The contacts must be closed (ring when dialed). Then place the tube in ice water (about 0°C...-5°C). If the contacts open and stop ringing, the device is working properly. If the circuit does not break in the cold or does not close in the heat, deep adjustment is required. thermostat.
To check, remove the thermostat and immerse its sensitive tube in a container of water at room temperature (about +20°C). The contacts must be closed (ring when dialed). Then place the tube in ice water (about 0°C...-5°C). If the contacts open and stop ringing, the device is working properly. If the circuit does not break in the cold or does not close in the heat, it is required replacement or deep adjustment.
⚠️ Attention: If the capillary tube of the thermostat has signs of corrosion, dents or damage to the insulation, it is useless to adjust such a device. The gas could escape, and the thermostat only needs to be replaced.
A common mistake is trying to adjust the thermostat with a faulty door seal. If warm air constantly enters the chamber, the compressor will work in increased mode, and no adjustment of the sensor will correct the situation. Always check the tightness of the door before tampering with the electrical system.
Step-by-step instructions for adjusting the thermostat K 59
The adjustment process requires accuracy and precision. On the body of the K 59 thermostat there are usually two adjusting screws hidden under a plastic case or seal. One screw is responsible for the temperature range (shifts the entire operating schedule), and the second is for the temperature difference (differential) between turning on and off.
☑️ Adjustment procedure
The first screw (often marked or located closer to the center) allows you to shift the temperature threshold. Clockwise rotation usually increases the temperature in the chamber (the compressor turns on less often), counterclockwise - decreases it. The second screw regulates the temperature difference. Reducing the differential causes the compressor to turn on more often, but work for less time.
The setup process is as follows:
1. Make half a turn of the adjusting screw.
2. Assemble the refrigerator and let it run for 30-40 minutes.
3. Measure the temperature in the chamber.
4. Repeat the procedure until the optimal result is achieved (+2...+5°C in the main chamber).
Do not try to set the ideal values the first time. The mechanics are inert, and the system takes time to stabilize. If you unscrew the screws too much, the contacts may stop closing at all, and the refrigerator will not start.
Parameter table other errors
When working with thermostats, it is important to understand the difference between the factory settings and actual operating conditions. Below is a table that helps interpret the behavior of the refrigerator depending on the position of the adjustments.
| Symptom | Probable cause | Action |
|---|---|---|
| The refrigerator does not turn on | Temperature threshold is too low | Rotate the range screw clockwise |
| Continuous operation without stopping | Temperature threshold is too high | Rotate the range screw against clockwise |
| Frequent on/off | Differential too small | Increase the temperature difference with the second screw |
| Food freezes at the back wall | Incorrect position thermostat | Check the fit of the tube to the evaporator |
One of common errors is incorrect installation of the sensing tube. It should fit tightly to the surface of the evaporator in a special seat. If the tube dangles in the air or is pressed on the wrong side, the temperature readings will be incorrect and adjusting the screws will not work.
Also, do not ignore the condition of the electrical contacts. Carbon deposits or oxidation on the terminals can create additional resistance, which leads to heating and false protection trips. Cleaning the contacts with fine sandpaper often solves the problem of the “floating” behavior of the refrigerator.
Replacing the thermostat: when adjustment does not help
There are situations when mechanical adjustment is no longer effective. If the bellows has lost its tightness or the membrane has become deformed over time, the device must be replaced. Fortunately, the thermostat K 59 is universal, and finding it in spare parts stores is not difficult.
When choosing an analogue, pay attention to the length of the capillary tube. It must be equal to or greater than the original length. If the new tube is longer, its excess can be carefully rolled into a ring and secured inside the housing without kinking or damaging it. Shortening the tube is strictly prohibited.
⚠️ Attention: When installing a new thermostat, make sure that the sensitive tube does not touch the moving parts of the fan (if there is one) and is not pinched by structural elements. This can lead to depressurization after a short time.
The replacement process takes about 30-40 minutes for an experienced user. The main thing is to connect the wires to the terminals correctly. An error in the connection can lead to a short circuit or operation of the compressor bypassing the thermostat, which is dangerous for the motor.
FAQ: Frequently asked questions
Is it possible to temporarily short-circuit the thermostat to make the refrigerator work?
Yes, by connecting the input wire to the wire going to compressor, you will start the motor directly. However, in this mode the refrigerator will run indefinitely until you unplug it. This is only permissible for short-term testing of the compressor or defrosting, but not for continuous operation, since the food will freeze and the motor may burn out from overheating.
Why, after replacing the K 59 thermostat, did the refrigerator start to turn on frequently?
Most likely, the new thermostat has a different differential (temperature difference) or was incorrectly adjusted with the adjusting screws. The cause may also be an insufficient amount of freon in the system or contamination of the condenser. Try tightening the differential screw a little, increasing the temperature range.
Where is the second adjusting screw on the K 59 thermostat?
Usually there are two holes on the K 59 body. One is often covered with a plastic cap or filled with paint. The second can be hidden under a layer of factory seal. Be careful when opening them: if the case is damaged, the device will lose its seal. Often the second screw regulates the hysteresis (temperature difference).
Is the K 59 thermostat suitable instead of the K 50 or T 110?
Thermostats of the K series (Danfoss) are often interchangeable with analogues of other series (for example, TAM or T) if the temperature ranges and mounting dimensions are the same. However, K 59 is designed for two-chamber refrigerators. Installing a sensor that is not suitable for the range will lead to either constant frost or a non-working refrigerator.