The situation when the refrigerator stops turning off or, conversely, refuses to start the compressor, most often indicates a failure of the thermostat. In most household models, especially manufactured Atlant, Indesit or Stinol, this type of relay is installed. Thermoregulator K59 is a key element of the temperature control system, opening and closing the compressor power circuit.
An inexperienced technician may find it difficult to replace this part due to the presence of many wires and the specific design of the capillary tube. However, the replacement process is quite possible to perform at home if you have a basic set of tools and an understanding of the operating principle of electrical circuits. It is important not only to physically install the new part, but also to connect the contacts correctly to avoid a short circuit.
Before proceeding with the dismantling of the old device, it is necessary to completely turn off the power to the refrigerator. This safety requirement is mandatory, since the work will be carried out with live electrical components. The K59 thermostat has three main contacts, and an error in connecting them can lead to burning out of the compressor or start relay. It is also worth preparing a multimeter in advance to check the integrity of the circuit and the functionality of the new part before final assembly.
The principle of operation and design of the K59 thermostat
The thermostat is an electromechanical device that responds to changes in temperature inside the evaporator. Inside the housing there is a bellows (sealed chamber) filled with refrigerant, which expands or contracts depending on external conditions. Capillary tube, emerging from the housing, is introduced into the cooling zone, transmitting temperature fluctuations to the sensitive element.
Unlike electronic sensors, K59 works mechanically. When the temperature reaches a set value, the pressure in the bellows changes and a click occurs - the contacts open or close. The model K59-L1102 or K59-L1275 may have different on and off parameters, as well as different lengths of the capillary tube, which is important to consider when selecting an analogue.
The main task of the relay is to maintain the temperature in the chamber, cyclically starting and stopping the motor. If the contacts stick, the refrigerator works without stopping, which leads to freezing of food. If the contacts do not close, the compressor is silent and the food begins to deteriorate. Understanding this cycle helps diagnose the problem faster.
Required tools and safety precautions
Successfully replacing the thermostat does not require complex professional equipment, but accuracy plays a crucial role here. You will need a standard DIY kit: screwdrivers (Phillips and flathead), pliers and, preferably, side cutters for trimming excess insulation. Also critical multimeter or at least a simple continuity test with a light bulb to check the electrical circuit.
☑️ Preparation for repair
Safety is not just words, but concrete actions. Working with electricity requires avoiding the risk of electric shock, so the power cord should be unplugged from the outlet well before disassembly begins. In addition, the capillary tube of the thermostat is very thin and fragile: it can easily be damaged by careless movement, which will make the new part unusable.
When working with plastic elements of the refrigerator interior, you should be careful, since in the cold the plastic becomes brittle (brittle). Sudden movements may cause chips or cracks on the inner walls of the camera. It is better to work slowly, giving the plastic time to adapt to room temperature if the refrigerator has just defrosted.
⚠️ Attention: The capillary tube should not be bent at an acute angle or twisted. The bending radius must be at least 5-6 mm, otherwise the tube will burst, the refrigerant will escape, and the thermostat will stop responding to temperature.
Removing the old thermostat
The process of removing the old relay begins with finding its location. In most refrigerators with a top freezer, the K59 thermostat is located inside the refrigerator compartment, often hidden behind a plastic panel or directly on the evaporator housing. In some models, the adjustment knob is moved outside, and access to the terminals is through a hole in the ceiling of the chamber.
First you need to remove the temperature control knob. Usually it is simply pulled onto the rod and removed with a slight effort. Under the handle you will see a nut or screw that secures the thermostat housing. After unscrewing the fasteners, the housing can be carefully removed. If the thermostat is built into the control panel, partial disassembly of the plastic box will be required.
The most crucial moment is disconnecting the wires. Before biting off or unsoldering wires, be sure to take a photo of the connection diagram or sketch which wire went to which terminal. Wire colors may vary from refrigerator to refrigerator, so you can't rely on color alone. Usually the terminals are numbered: 3, 4, 6. The ground wire (yellow-green) is often attached with a separate screw to the thermostat body or metal frame.
What to do if the wires are mixed up?
If you forgot take a photo of the circuit, use a multimeter in testing mode. Find a pair of contacts that ring at room temperature (this is working pair 3-4). The third contact (6) is usually a contact for an indicator or emergency mode; it closes during strong cooling or manually with a button.
After turning off the electrics, you need to remove the capillary tube from the evaporator. It can be glued or simply inserted into the hole. Be careful not to damage the aluminum evaporator tubes, which are also very susceptible to mechanical damage. If the tube is glued, you can carefully pry it off with a knife, but without fanaticism.
Connection diagram and contact marking
Correct connection of the thermostat K59 is the key to a successful repair. The device body always has terminal markings, which are standardized for most manufacturers. Understanding the purpose of each contact will help you avoid mistakes. The main terminals are designated by numbers 3, 4 and 6.
Contact 3 and contact 4 is the main working pair. It is through them that the current passes to the compressor. Under normal conditions (at room temperature), these contacts should be closed. If you test these two terminals with a multimeter and hear a squeak, the circuit is intact. The contact 6 is used to connect an operation indicator (light bulb) or, in some circuits, for the fast freezing mode.
The following is a table describing the typical pinout for thermostats of the K59 series:
| Terminal number | Purpose | State at room temperature | Wire color (typical) |
|---|---|---|---|
| 3 | Power input (from mains) | Closed with 4 | Red / Brown |
| 4 | Output to compressor | Closed with 3 | Black / Orange |
| 6 | Indicator / Freeze | Open | Yellow / Green |
When connecting a new thermostat, follow the diagram that was on the old device. If you are using a universal analogue, check its passport data. Sometimes the numbering on universal models may differ, so checking with the instructions for a specific article is mandatory. Do not forget to securely fasten the ground wire if it was present in the design.
Installation of a new thermostat and calibration
After checking the new thermostat for functionality (continuity of contacts 3-4 should show the circuit), you can begin installation. Insert the capillary tube into the evaporator hole at the same depth to which the old one was immersed. The optimal immersion depth is usually from 6 to 10 cm, but it is better to focus on bending marks on the old tube.
Fix the thermostat housing in its original place. Make sure that the wires are not pinched by the refrigerator body or door. Place the capillary tube around the perimeter of the evaporator or in a specially designated groove, avoiding sharp bends. If the original tube is too long, it can be carefully twisted into a ring with a diameter of at least 4-5 cm and secured next to the thermostat housing.
After assembling the electrical part and installing the plastic panels, the refrigerator can be turned on. However, you shouldn't download products right away. First, you need to let the unit idle to get into operation. The first cycles may be longer than usual as the system needs to stabilize.
Typical errors and fault diagnosis
Even with correct installation, nuances may arise. Often, beginners forget about the grounding contact, which can lead to the appearance of potential on the refrigerator body (“electric shock”). Another common mistake is poor contact in the terminal block. If the wires are simply twisted and poorly insulated, over time they will oxidize and the contact will be lost.
It happens that a new thermostat is installed, but the refrigerator does not turn off. This may mean that the capillary tube is not immersed deep enough in the cooling zone or is not in good contact with the evaporator. In some cases, additional fixation of the tube with thermal paste or aluminum tape is required to improve heat transfer, although this is rarely done in household K59 models.
⚠️ Attention: If, after replacing the thermostat, the compressor hums but does not start, immediately turn off the device. Probably, the problem is not in the thermostat, but in the starting relay or the compressor itself, or you have mixed up the contacts, and the phase does not reach the motor.
It is also worth checking whether the capillary tube does not touch moving parts (if we are talking about defrosting) or vibration units. Constant vibration can cause the thin tube to break. If you hear unusual sounds or see that the tube is rubbing against metal, secure it with plastic clamps.
Frequently asked questions (FAQ)
Is it possible to install a K59 thermostat from another manufacturer, for example, TAM?
Technically, it is possible if the mounting dimensions and length match capillary tube. However, thermostats TAM and K59 may have different temperature response ranges. K59 is usually designed for single-chamber refrigerators or double-chamber refrigerators, while TAM is often used for freezers. Setting the wrong range will result in an incorrect temperature in the chamber.
Why does the refrigerator turn on too often after replacing the thermostat?
This may be due to incorrect installation of the capillary tube. If it is not cooled enough, the thermostat will “think” that the chamber is warm and will often turn on the compressor. It is also possible that you purchased a thermostat with a narrower differential range (the difference between turning on and off) than it originally had.
Do you need to defrost the refrigerator before replacing K59?
Yes, complete defrosting is required. First of all, it's safe. Secondly, in the defrosted state, the plastic becomes more elastic, and the risk of breaking the panel fastenings or damaging the evaporator when manipulating the tube is significantly reduced. Working with an ice-covered evaporator is extremely difficult and risky.
What to do if the new regulator handle does not fit the size of the rod?
Rods from different manufacturers may differ in diameter and shape (D-shaped, round, with a slot). If the handle from the old thermostat does not fit on the new one, you can try to carefully bore the hole in the handle or use an adapter if it is included. As a last resort, adjustment can be made with a flat screwdriver through the hole, although this is less convenient.
How to check whether the new thermostat is working before installation?
Use a multimeter in resistance measurement mode (Ohm). At room temperature, the probes on pins 3 and 4 should show “0” or a value close to zero (the circuit is closed). If you put the sensitive element (capillary) in the freezer or press it against ice, after a while a click should be heard and the resistance should become infinite (the circuit will open). This indicates the serviceability of the mechanics.