The situation when in the refrigerator the light suddenly stops turning on, and the food begins to become covered with an ice crust or, conversely, quickly deteriorates, often indicating a breakdown thermostat. This small but critical element is responsible for maintaining the set temperature inside the chambers by closing and opening the electrical circuit of the compressor. If you notice that the motor hums continuously without stopping or turns on extremely rarely, ignoring the position of the control knob, most likely it is time to replace the sensor.
Self-installing the thermostat is a task quite feasible for a person with basic skills in working with tools, but it requires care and compliance with safety precautions. Improper installation can lead to food spoilage or even compressor failure, so it is important to clearly understand the operating principle of the device. In this article we will look at how to correctly diagnose a malfunction, select an analogue and perform a replacement without calling a technician.
Before proceeding with disassembly, it is necessary to de-energize the unit. Working with electrical components requires a complete absence of mains voltage. Refrigerator should be left unplugged for a while to allow the refrigerant to stabilize and for you to work safely with the wiring. Preparing the workplace and having the necessary tools are the key to successful repairs.
Diagnostics and signs of thermostat malfunction
Understanding the symptoms allows you to avoid unnecessary disassembly. Thermostat is a mechanical or electronic switch that responds to changes temperature. When it breaks, the circuit either opens forever (the compressor is silent) or closes tightly (the unit works without interruption). In the first case, you will see defrosted food, in the second - a “coat” of ice on the walls and back wall.
There is a simple method of initial checking that does not require a multimeter. If the refrigerator does not turn on, you can try to close the contacts of the wire coming from the thermostat directly. If the engine starts after this manipulation, then the problem is in the sensor. However, this method requires caution and an understanding of electrical circuits.
⚠️ Warning: If your refrigerator makes strange sounds (clicking, humming) before attempting to start, but does not turn on itself, the problem may be with the start relay or the compressor itself, rather than with the thermostat. Do not change the sensor blindly if you are not sure of the diagnosis.
For more accurate diagnostics, use a multimeter in dial mode. At room temperature, the contacts of a working mechanical thermostat should ring. If you place the sensing tube in the freezer (or otherwise cool it), the circuit should open with a characteristic click. Lack of reaction indicates the need for replacement.
Choosing the appropriate thermostat model
The spare parts market offers many options, and it is important not to make a mistake with the choice. There are practically no universal solutions here, since temperature range and the length of the capillary tube can vary significantly between different models. Using an unsuitable sensor will lead to incorrect operation of the equipment.
First of all, you need to focus on the markings on the body of the old device. Even if the original thermostat has been discontinued, using its code (for example, TAM-133 or K-59) it is easy to find a modern analogue from manufacturers like Danfoss, Ortal or Thermoreg. It is important to pay attention to the number of contacts and their location.
Pay special attention to the length of the capillary tube. It can vary from 0.5 to 3 meters. If you buy a thermostat with a tube that is too short, you may not have enough length to fit properly in the evaporator, which will skew the temperature reading. A tube that is too long can be carefully twisted, but not bent.
| Marking | Refrigerator type | Tube length | Features |
|---|---|---|---|
| TAM-133 | Single chamber | 0.73 m | Standard for old models |
| K-59 | Two-chamber | 2.5 m | Popular analogue for Indesit/Ariston |
| TAM-145 | Freezer | 1.3 m | For low temperatures (-18°C and below) |
| K-50 | Single chamber | 0.75 m | Analogue TAM-133, often interchangeable |
When purchasing, pay attention to the presence of a grounding contact. If your model was designed to have one, the new thermostat should also have a ground terminal. This ensures safe operation and protection from stray currents.
Necessary tools and preparation for work
To successfully replace the thermostat, you do not need complex industrial equipment, but a set of tools should be at hand. The main emphasis is on accuracy, since the plastic elements of the case and the fragile capillary tube are easily damaged if handled carelessly.
You will need the following tools:
- 🔧 Screwdrivers (Phillips and flathead) for removing panels and terminals.
- 🔍 Multimeter for checking circuits and diagnostics.
- 🧤 Gloves to protect hands from sharp edges and dirt.
- 📸 Smartphone for fixing the wiring diagram.
Before starting work, be sure to defrost the refrigerator if there is ice in it. Water may get on the electrical contacts, causing a short circuit. Also clear the space around the unit to allow easy access to the rear wall and internal panels.
It is important to prepare a container to collect water and rags. Even if you do not defrost completely, condensation may appear when you dismantle the internal elements. The cleanliness of the workplace is the key to ensuring that small screws do not get lost and water does not flood the wiring.
☑️ Preparation for replacement
Removing the old thermostat
The process of removing the old sensor depends on the design of your refrigerator. In most models, the thermostat is located inside the refrigerator compartment, under the lamp shade or behind a decorative panel. In some cases, access is through the rear wall from the outside.
First remove the temperature control knob. It can fit tightly, sometimes requiring a little rocking. Then remove the screws securing the thermostat housing. Be careful: the plastic often hides latches that can easily be broken with a sharp tug. The plastic on old refrigerators becomes brittle.
After gaining access to the electrical part, take a photo of the wire connections. This critical momentsince the color marking of the wires may not comply with the standards, and you cannot rely on colors alone. Carefully disconnect the terminals by pulling the metal tip, not the wire itself.
⚠️ Attention: The thermostat capillary tube is very thin and is easily pinched. Don't pull hard on it. If the tube is glued to the evaporator, carefully cut the adhesive or release the fasteners, being careful not to damage the aluminum tubes of the evaporator.
Remove the sensing tube from the hole in the chamber. It can pass through seals or special bushings. Remember or write down the path it follows so that when installing a new element, repeat the trajectory exactly. Incorrect position of the tube will result in incorrect temperature readings.
What to do if the tube breaks inside?
If the capillary tube breaks off at the base inside the refrigerator body, do not try to remove the remainder by force. Carefully push the new thermostat with the new tube down the same channel, using the old one as a guide if possible, or release carefully.
Installation of a new thermostat and connection
Installation of a new element begins with the preparation of the capillary tube. If its length exceeds the required one, the excess must be carefully twisted into a spiral with a diameter of at least 40 mm. It is strictly forbidden to bend the tube at an acute angle or flatten it, since there is gas or liquid inside, and breaking the seal will damage the thermostat instantly.
Pass the tube into the camera hole along the same path as the old one. Place the sensitive element in its standard place on the evaporator or in a special pocket. The fixation must be reliable: use standard clamping strips or special heat-resistant glue/adhesive tape, if provided for by the design. Poor contact with the surface of the evaporator will lead to the sensor “lying.”
Connect the wires according to the photograph taken earlier. If you forgot to take a photo, look for markings on the terminals: usually these are numbers or letters (L, 1, 2, 4). The ground wire (yellow-green) is connected to the housing or a special terminal. Make sure that the contacts fit tightly and do not loosen.
Fix the thermostat housing to the seat with screws. Install the adjustment knob. Check that nothing is preventing the panels and lamp shade from closing. Assembly is carried out in reverse order. Don't forget to check if the wires are pinched by the door or plastic elements.
Setting up and checking operation
After installing a new thermostat, you should not immediately load food. Turn on the empty refrigerator and let it run in test mode. The initial adjustment of the knob is usually made to the middle position (often this is number 3 or 4 on the scale).
During the first few hours of operation, listen to the unit. The compressor should turn on, cool the chamber to the set temperature and turn off. Work cycles should be uniform. If the motor runs without stopping for more than 2-3 hours and does not turn off, perhaps the thermostat does not sense the cold or its settings are off.
The temperature is checked using an external thermometer placed in a glass of water in the center of the chamber. After 6-8 hours of operation, the temperature in the main chamber should drop to +2...+5°C, and in the freezer - to -18°C and below. If the indicators are very different, additional adjustment may be required.
- 🌡️ If the refrigerator freezes poorly and does not turn off for a long time, the tube may not be in good contact with the evaporator.
- ❄️ If the chamber freezes and the food is covered with ice, check whether the tube is set too deep or knocked down caliber.
- 🔌 If the compressor does not start at all, double-check the electrical contacts and the presence of voltage at the input.
Some models of mechanical thermostats have an adjusting screw under the seal or inside the case, which allows you to shift the temperature range. However, you shouldn’t go there without special equipment and knowledge. It is better to rely on the factory settings of a high-quality analogue.
⚠️ Attention: Refrigerator manufacturers can change the design and location of components in different modifications of the same series. If you see that the internal structure of your unit differs from the description, check the official technical documentation or diagram for a specific model.
Is it possible to use a universal thermostat?
There are universal models with adjustable tube length and temperature range. They are convenient to have, but require fine tuning. For a beginner, it is better to find an original analogue or a high-quality substitute for a specific model.
Frequent questions and answers (FAQ)
Is it possible to replace a mechanical thermostat with an electronic one?
Theoretically it is possible, but this requires a deep rework of the refrigerator control system. Electronic sensors operate on a different principle and require an appropriate controller. A simple one-to-one replacement will not work here; it is better to install a similar mechanical or electronic control unit, if it is provided by the factory.
Why does the new thermostat click, but does not turn on the compressor?
A click means that the mechanism has worked, but the circuit does not close. Possible reasons: the contacts inside the new thermostat have oxidized (defective), the wires are connected incorrectly, or the problem lies deeper - in the start relay or compressor windings. It is necessary to test the circuit with a multimeter.
How often should the thermostat be changed?
The service life of the thermostat is usually 5-10 years or more. It does not require scheduled replacement, only when it fails. Frequent breakdowns can be caused by power surges or mechanical damage when cleaning the refrigerator.
Is it dangerous to change the thermostat yourself?
The main danger is electric shock if safety rules are not followed (working under voltage) and the risk of damaging the cooling system (piercing the evaporator with a screwdriver or squeezing the tube). If you are confident in your abilities and careful, the risk is minimal.