Sudden stoppage of operation refrigerator or, conversely, its endless operation with the constant formation of a fur coat - these are signs that cannot be ignored. Often the root of the problem lies in a small but critical control element - thermostat (thermostat). It is this device that is responsible for maintaining the set temperature inside the chambers, opening and closing the electrical circuit of the compressor at the right moment.
If you notice that food has begun to deteriorate faster than usual or a thick layer of ice has formed on the walls, and the compressor is humming without interruption, then it is probably time to check capillary tube and sensor contacts. Repairing this unit can be done by a home craftsman with a minimum set of tools and basic knowledge of electrics. However, before starting any work, it is necessary to completely de-energize the unit by removing the plug from the socket.
In this article we will analyze in detail the algorithm for diagnosing and replacing a failed control element. You will learn how to choose the right analogue, what to pay attention to when dismantling an old device and how to avoid common mistakes that can lead to compressor failure. A competent approach will extend the life of your refrigerator and save on calling a technician.
Symptoms of a malfunctioning thermostat
Understanding what exactly is broken is half the success in repairs. A thermostat is a mechanical or electronic device that wears out over time. Most often, the contacts stick or the bellows, which contain freon gas, lose their tightness. When the gas evaporates through microcracks, the device stops “feeling” the temperature and does not give a signal to turn the motor on or off.
The malfunction can be determined by a number of characteristic signs that appear in the operation of refrigeration equipment. If the compressor does not start at all, but the light inside is on, this may indicate an open circuit in the thermostat itself. In the opposite situation, when the motor runs without stopping and does not turn off even at night, we can say that the contacts are “stuck” in the closed state.
⚠️ Attention: If the refrigerator runs without interruption, this creates a colossal load on the compressor, which can lead to its thermal burnout. Do not delay diagnostics!
There is another important nuance that is often overlooked. In refrigerators with No Frost a faulty sensor may prevent the defrost system from starting, which is why the evaporator becomes overgrown with ice and stops passing cold air. As a result, the chamber is warm, although the compressor may be running. It is also worth checking whether the sensor tube itself has moved from the evaporator wall.
The following are the main symptoms that should alert the owner:
- ❄️ The compressor works continuously without going into rest mode, and the temperature in the chamber drops below normal.
- 🔌 Motor-compressor does not turn on at all, although there is voltage in the network and the light lamp is on.
- 💧 In the refrigerator compartment there is a constant “crying” wall or, conversely, a complete absence of condensation and dryness of the products.
- 🔊 Frequent clicking of the relay when trying to start, which indicates unstable operation of the control circuit.
Diagnostics before starting work
Before disassembling the housing and buying new spare parts, you need to make sure that the problem lies in the thermostat, and not in the start relay or the compressor itself. The simplest and most reliable way to check is the elimination method. To do this, you will need to close the contacts on the thermostat directly, allowing current to bypass the sensor. If after this procedure the compressor starts and works, then the thermostat is to blame.
To carry out diagnostics, you will need a multimeter (tester) in dial mode. First you need to get to the device itself. In most models, it is located inside the refrigerator compartment under a plastic cover or in the control unit on top. After removing the protective cover, you will see the wires going to the thermostat terminals.
The test process is as follows: remove the wires from the terminals and connect them together (being careful, since this is done only for testing, and not for long-term operation). If the compressor starts working when it closes, the diagnosis is confirmed. You can also “ring” the sensor itself with a multimeter. At room temperature the contacts should be closed (resistance close to zero). If you put the sensor in the freezer for 10-15 minutes, the circuit should break (the resistance is infinite).
Nuances of checking electronic thermostats
In modern models with electronic control (where there is a display), mechanical testing may not give an accurate result, since there is a thermistor there. Its resistance changes smoothly depending on temperature. To check such sensors, you need to know the exact resistance values at different temperatures, which can be found in the service manual of a specific model.
One of them can go to the operation indicator light or to the fan. When calling, it is important not to confuse contact groups. Typically, the wiring diagram is marked on the body of the device itself or is indicated in the technical documentation.
Tools and preparation for repair
Replacing a thermostat is a procedure that does not require complex industrial equipment, but accuracy plays a decisive role here. You won't need huge wrenches, but a set of small screwdrivers and pliers will be indispensable. The main thing is to prepare a workplace with good lighting in order to see the markings of the wires and the condition of the fasteners.
Before starting work, make sure that you have everything you need at hand. Not having the right screwdriver can cause the screw slots to break off, making assembly much more difficult. It is also worth preparing a container for defrosting if during the process you will have to keep the refrigerator turned off for a long time, although the replacement process itself is usually quick.
☑️ Tools for replacing the thermostat
Pay special attention to safety. Even though we are working with a de-energized appliance, residual effects may remain in the circuits, and sharp edges of metal shelves or housing may injure your hands. Wear gloves if convenient, and use a dielectric mat if the floor is concrete.
List of necessary tools and materials:
- 🔧 Set of screwdrivers (Philipps Ph1, Ph2 and flat).
- 🔌 Multimeter for checking circuit integrity.
- ✂️ Pliers or side cutters for cutting and fixing wires.
- 🧤 Dielectric gloves (optional, for safety).
- 🧼 Dry rags for wiping contacts from dust and moisture.
Step-by-step instructions for replacing the thermostat
The replacement process may vary slightly depending on the refrigerator model (Indesit, Atlant, Bosch or LG), but the general principle remains united. First you need to gain access to the sensor mounting location. In classic models, the thermostat is often hidden under the lampshade or behind a decorative panel on the ceiling of the chamber.
Carefully remove the plastic plugs and unscrew the mounting screws. Do not use excessive force, as the plastic on older refrigerators can be brittle and breakable. After removing the panel, you will see the thermostat block itself with a long one coming out of it capillary tube. This tube is secured to the evaporator with special brackets or clips.
Next follow the algorithm:
1. Disconnect the wires from the terminals of the old thermostat, having first remembered or photographed their order.
2. Release the capillary tube. Usually it is held on by latches or screws that press it to the surface of the evaporator.
3. Carefully pull the tube out of its seat. Be careful not to damage the thin copper tube as it is filled with gas under pressure.
4. Install the new thermostat, securing the tube in the same places where the old one was. The length of the free part of the tube must correspond to the original.
5. Connect the wires according to the diagram and fix the device body.
⚠️ Attention: The capillary tube is very sensitive to kinks and shocks. If you bend it or damage the shell, gas will escape and the new thermostat will immediately become faulty. Do not use adhesive tape or electrical tape to secure it - only standard clips.
After installation, reassemble the case in the reverse order. Make sure that all the latches are in place and that the wires are not pinched by the case walls. Only after complete assembly can you plug in the refrigerator.
Compatibility table and selection of analogues
One of the main difficulties during repairs is finding a suitable spare part. Thermostats from different manufacturers may have a similar appearance, but differ in the length of the capillary tube, operating temperature range and contact arrangement. Using an unsuitable analogue may result in the refrigerator freezing too weakly or, conversely, freezing everything in ice.
When purchasing, pay attention to the labeling. For example, thermostats TAM are often analogues K series, but may have different tube lengths. Refrigerators with No Frost and drip systems require different types of sensors. Also important is the on and off temperature, which is programmed into the factory settings of the spring.
Below is a table for the approximate selection of analogues (data may vary depending on the specific modification):
| Original (Marking) | Possible analogue | Tube length (mm) | Application |
|---|---|---|---|
| K-50 / K-52 | TAM-112 / TAM-133 | 0.6 - 2.5 m | Single-chamber, double-chamber |
| K-56 / K-57 | TAM-125 | 0.6 - 2.5 m | Refrigerators with No Frost |
| K-59 | TAM-133 | 1.3 - 2.5 m | Two-chamber (main chamber) |
| 145002 (Indesit) | TAM-133 (with modification) | Depends on models | Specific models Indesit/Ariston |
If you do not find an exact match in stores, you can use universal thermostats with adjustable tube length, but their installation requires more qualifications. In such cases, it is better to consult with a sales consultant in a specialized spare parts store, naming the exact model of your refrigerator.
Setup and first launch
After the replacement is made and the refrigerator is assembled, the testing stage begins. Do not immediately load food into the chambers. Let the equipment run idle for at least 2-3 hours. During this time, the refrigerator should reach the desired temperature and turn off. This will be a signal that the thermostat is working correctly and opens the circuit.
Pay attention to the temperature control knob. During the first launch, try turning it to different positions. You should hear a characteristic click when the temperature reaches the trigger threshold. If there is no click, but the compressor continues to hum or is silent, the thermostat may be defective or incorrectly installed.
⚠️ Attention: If, after replacing the thermostat, the refrigerator turns on and immediately turns off (the cycle lasts several seconds), there may be a short circuit in the circuit or a faulty start relay, which could have been damaged by power surges before repair.
In models with electronic control, after replacing the sensor, errors may need to be reset. This is done by pressing certain buttons on the control panel for a long time or temporarily turning off the power (for 15-20 minutes). Look for information about error codes and reset methods in the instructions for your model.
What to do if the temperature does not hold?
If after replacing the thermostat the temperature in the chamber does not stabilize, check the tightness of the capillary tube to the evaporator. Poor contact leads to a delayed sensor response. Also, the cause may be a freon leak from the cooling system, which no longer applies to thermostat repair.
Frequently asked questions (FAQ)
Is it possible to temporarily operate a refrigerator without a thermostat?
Theoretically, it is possible if you close the contacts directly, but this is dangerous. The compressor will run continuously, which will lead to freezing of food, overloading the motor and high energy consumption. This solution is only valid for a few hours while you wait for the courier with the spare part.
Why does the new thermostat click but does not turn on the compressor?
Most likely, the problem is not in the thermostat, but in the compressor start relay or in the engine itself. The thermostat only gives a signal, and the relay executes it. It is also worth checking the integrity of the wires going from the thermostat to the motor.
What is the difference between a thermostat for a refrigerator and a freezer?
They have different operating temperature ranges. The thermostat for the freezer is set to lower values (for example, from -18°C to -24°C), and for the refrigerator to positive values (from 0°C to +10°C). Installing an unsuitable sensor will lead to incorrect operation.
How to determine that the capillary tube is empty (faulty)?
If, when the tube is cooled (for example, in a freezer), you do not hear a click of the contacts opening and the multimeter shows a constant circuit (or a constant break, depending on the type), then the gas has evaporated and the bellows is not responds to temperature.
Is it necessary to evacuate (pump out) the system when replacing the thermostat?
No. The thermostat is located in the electrical control circuit and its capillary tube is sealed separately from the refrigerant circuit. When replacing it, the tightness of the refrigerator cooling system is not compromised, and calling a technician with a vacuum pump is not required.