System failure Automatic shutdown of the compressor is one of the most common reasons why the refrigerator stops maintaining the set temperature. Most often, the culprit is the thermostat K59, which over time loses its calibration properties or fails due to power surges. Understanding the principle of operation of this unit and the ability to replace it will allow you to save a significant amount on calling a technician and return the equipment to working order in one evening.
Thermostat K59 (often labeled as Danfoss or Ranco) is an electromechanical device that responds to changes in temperature in the evaporator. When the air inside the chamber heats up to a certain threshold, the contacts close, starting the motor-compressor. When the desired cold is reached, the bellows contracts, opening the circuit. If your refrigerator starts working without interruptions or, conversely, does not turn on at all, and the food is melting, then most likely the problem lies in this element.
In this article we will analyze in detail the diagnostic process, dismantling the old sensor and installing a new regulator. We will pay special attention to the nuances of connecting wires, since this is where mistakes are most often made, leading to repeated repairs. The correct sequence of actions and compliance with safety measures guarantee the successful restoration of the functionality of your refrigerator.
Diagnostics of a malfunction of the K59 thermostat
Before disassembling the refrigerator, you need to make sure that the problem lies in the thermostat, and not in the compressor or start relay. The primary sign of a malfunction thermostat is the absence of a characteristic click when turning the temperature control knob. If you turn the knob from minimum to maximum, and there is no sound of contacts opening or closing, this is a good signal for further checking.
For accurate diagnostics, you will need a multimeter switched to continuity mode. After removing the handle and dismantling the thermostat from the housing, you need to disconnect the wires from it and check the contacts. In normal condition (at room temperature), the contacts should be closed and the device will emit a sound signal. If the device shows a break, it means that the internal mechanics K59 is broken.
⚠️ Attention: Before starting any diagnostic and repair work, be sure to disconnect the refrigerator from the electrical network! Working with live electrical wiring is deadly.
Sometimes a thermostat may be electrically correct, but not respond correctly to temperature due to a bellows leak or miscalibration. In this case, the refrigerator may turn off too early, not freezing food, or run continuously, creating a crust of ice. Replacing the element in such cases is the only reasonable solution, since repairing internal components thermostat in domestic conditions is impossible.
Necessary tools and preparation for work
To successfully replace the thermostat K59 you No complex industrial equipment is required, but a basic set of tools should be at hand. It is important to prepare a work area with good lighting, since inside the refrigerator compartment and behind the back wall it is often dark, and the wires have a similar color.
You will need the following tools:
- 🔧 Screwdrivers of different types (phillips and flat) for removing panels and terminals.
- 🔪 Sharp sharpened knife or side cutters for stripping wire insulation.
- 🧤 Pliers for reliable clamping of contacts and manipulation with the sensor tube.
- 🧵 Insulating tape or heat-shrink tubes for insulating joints.
- 🧼 Clean rags for wiping internal surfaces from condensation and dust.
Particular attention should be paid to the new thermostat. The model K59 has several modifications that differ in the length of the capillary tube and temperature range. For example, single compartment refrigerators and freezers have different versions. Make sure that the markings on the body of the new device match the requirements of your refrigerator model, otherwise the temperature regime will be disrupted.
It is also recommended to photograph the wiring diagram in advance before disconnecting them. Wire colors may vary depending on the refrigerator manufacturer, and visual memory is your best guide here. If you plan to solder connections, prepare a soldering iron and solder, although in most cases high-quality twisting and insulation is sufficient.
Removing the old thermostat
The process of removing the old thermostat begins with clearing access to it. In most refrigerators where K59is used, the regulator is located inside the refrigerator compartment, often hidden by a plastic cover or located next to the light lamp. Carefully remove the adjustment knob by pulling it towards you and unscrew the mounting screws holding the thermostat housing.
After removing the housing, you will see a bellows tube that enters the evaporator or is pressed against it with a special plate. Capillary tube very thin and sensitive to damage, so you need to act with extreme caution. If the tube is secured with a screw, unscrew it. If it is simply inserted into the hole, carefully pull the thermostat towards you, trying not to jerk the tube sharply.
☑️ Preparation for dismantling
When the housing is removed, move on to the electrical part. The thermostat K59 usually has three or four contacts. The wires can be secured to the terminals with screws or simply pushed onto the pins. In the first case, loosen the screws with a screwdriver, in the second, carefully tighten the terminals with pliers, holding the wire itself so as not to damage it.
After disconnecting all the wires, the old thermostat can be considered dismantled. However, if you plan to install a new sensor with a different length of capillary tube, you may need to carefully remove the remains of the old tube from the process channel in the refrigerator wall. Do this smoothly, without jerking, so as not to damage the internal channel or evaporator.
Connection diagram and installation of a new sensor
Installation of a new thermostat K59 is done in the reverse order of dismantling, but taking into account several important nuances. The most critical point is the correct connection of the wires to the contact group. On the body of the new thermostat, the contacts are numbered (usually 3, 4, 6), and their purpose may differ from the old regulator, even if they look the same.
The standard connection diagram for most refrigerators with a thermostat K59 looks like this:
| Contact on K59 | Purpose | Wire color (approximate) | Where to connect |
|---|---|---|---|
| 3 | Network input (Phase) | Red / Brown | From power cord / relay |
| 4 | Output to compressor | Black / Green | Motor start relay |
| 6 | Output to lamp/fan | White / Yellow | Camera lighting lamp |
It is important to understand that the colors of the wires in the table are given as indicative. In different models of refrigerators (Indesit, Ariston, Stinol, Beko), the color marking may vary. The only reliable way to determine the correct connection is to check the circuit with a multimeter: when turning the knob to the "maximum" position, the pair of contacts going to the compressor should ring.
After connecting the electrical part, it is necessary to correctly place the capillary tube. It should be inserted into the same hole as the old one, and pressed with the same plate. Model tube length K59 often is about 0.75 meters, and its excess is carefully rolled into a ring with a diameter of at least 4-5 cm inside the thermostat housing or behind the rear panel, so as not to damage the fragile metal.
⚠️ Attention: The capillary tube is filled with freon under pressure. Never bend the tube at an acute angle or allow it to be struck. Damage to the tube will lead to the release of gas and complete inoperability of the thermostat.
Setting and calibrating the temperature mode
After installing a new thermostat and assembling the refrigerator, you should not expect an instant perfect result. The system needs time to stabilize. It is recommended to carry out the initial adjustment with empty chambers so that the heat capacity of the products does not distort the readings.
Set the adjustment knob to the middle position (usually this is the number 3 or 4 out of 7 possible). Plug in the refrigerator and let it run for 5-6 hours. During this period, do not open the doors frequently so as not to disturb the temperature balance. The compressor should turn on and off cyclically.
If after the first cycle of operation you notice that the refrigerator turns off too early (food does not freeze) or works without stopping (a “fur coat” forms in the chamber), mechanical adjustment is required. On the thermostat body K59 there is often an adjusting screw, which can be accessed through a special hole or after removing an additional cover.
Rotating the screw clockwise usually increases the shutdown temperature (the refrigerator will turn off at a higher temperature, that is, work less). Rotating counterclockwise lowers the shutdown temperature (the unit will freeze more strongly). Adjustments should be made in small steps (1/4 turn), waiting for a full cycle of work after each change.
Frequent connection errors and their consequences
Even experienced craftsmen sometimes make mistakes that can lead to repeated equipment failure. One of the most common problems is the incorrect connection of the wires to pins 3, 4 and 6. If the wires going to the compressor and the lamp are mixed up, the lamp may remain on constantly, even when the door is closed, which will lead to overheating of the chamber and continuous operation of the motor.
Another common mistake is poor contact in the connection of the wires. If you use twisting, it should be as tight as possible and preferably soldered. Poor contact causes sparking, heating and eventual melting of the insulation, which can cause a short circuit. The use of high-quality electrical tape or heat shrink is critical here.
What will happen if you do not press the capillary tube?
If the capillary tube of the K59 thermostat is not pressed tightly to the evaporator or inserted into the channel all the way, the thermostat will “see” the temperature of the air in the chamber, and not the temperature of the evaporator. This will lead to large delays in the reaction: the refrigerator will turn off too late, causing heavy ice accumulation, or turn on too rarely.
It is also worth mentioning the error associated with ignoring tightness. After installing the new thermostat, make sure all seals and gaskets are in place. If warm, humid air from the room gets into the hole from which the tube came out, condensation and ice will inevitably form in this place, which can damage the wiring or the evaporator itself.
⚠️ Attention: Specifications and location of elements may vary depending on the specific refrigerator model and year of manufacture. Always check the manufacturer's technical documentation, if available, especially when working with modern models that have complex electronics.
Questions and answers (FAQ)
Is it possible to install a K59 thermostat instead of a K50 or TAM?
In most cases, replacement is possible, but requires careful study parameters. Thermoregulators K59 and K50 have different temperature ranges and capillary tube lengths. K59 is often used in single-chamber refrigerators, and K50 in double-chamber refrigerators. Installing the wrong model will lead to incorrect operation: either the refrigerator will not turn off or will not be able to reach the desired temperature.
Why does the new thermostat click, but the refrigerator does not turn on?
If you hear a click, this means that the mechanics thermostat works. The problem most likely lies in incorrect connection of the wires to the contacts, a malfunction of the compressor itself, the start relay, or an open circuit in the power supply. It is necessary to re-check the connection diagram with a multimeter, ringing the circuit from the socket to the entrance to the compressor.
How to determine that the capillary tube is not inserted deep enough?
The main symptom is incorrect temperature conditions. If the tube does not reach the sensing element area or is not pressed well, the thermostat responds late. It is difficult to check this visually without disassembling, but if the refrigerator continues to operate jerkily or does not keep cold, it is worth checking the tightness of the tube to the evaporator.
Does it need to defrost the refrigerator before replacing the thermostat?
Yes, complete defrosting is required. Firstly, it is safe for electricians. Secondly, ice can hide fasteners or interfere with access to the capillary tube. Thirdly, moisture formed when ice melts during operation can get onto the electrical contacts of the new thermostat, causing corrosion or a short circuit.