Sudden defrosting of food in the refrigerator or, conversely, the formation of an ice crust on the walls often indicates a failure in the system thermoregulation. The heart of this system is thermostat (or thermal relay), which is responsible for turning the compressor on and off depending on the temperature inside the chambers. If this unit fails, the refrigerator ceases to maintain the set mode, which can lead to food spoilage or overheating of the motor.
Replacing the thermostat is a procedure that many owners of household appliances try to perform on their own in order to save on calling a technician. However, this process requires care, a basic understanding of electrical appliances and compliance with safety precautions. In this article, we will look in detail at how to diagnose a breakdown, select the right part and replace it without the risk of damaging other components of the unit.
Before starting disassembly, you need to make sure that the problem lies in the thermostat, and not in a freon leak or a compressor malfunction. Thermal relay is a mechanical or electronic device that wears out over time, and its contacts may stick or, conversely, open prematurely. Understanding the operating principle of this element will help you avoid mistakes during repairs and extend the life of your refrigerator.
⚠️ Attention: Any work on repairing the refrigerator should be carried out only after completely disconnecting the device from the power supply. Failure to comply with this rule may result in electric shock.
Signs of a malfunctioning thermostat
Determine what thermostat out of order, this can be determined by a number of characteristic signs that appear in the operation of the refrigeration chamber. Most often, users notice that the refrigerator either stops turning on at all, or works continuously, not turning off even when ice has formed inside. In the first case, the relay contacts could oxidize and stop closing the circuit, in the second, they were “stuck” in a closed state.
Another symptom is incorrect operation of the temperature regime. Food in the refrigerator compartment can either freeze, turning into ice blocks, or, conversely, quickly deteriorate due to insufficient cooling. If you turn the temperature regulator, but the nature of the motor operation does not change, this is a sure sign that thermal relay does not respond to your actions.
- 🔊 The compressor hums, but does not start, or starts for a few seconds and immediately stalls.
- ❄️ Ice has formed inside the chamber, although the regulator is set to minimum cooling.
- 🌡️ The temperature in the chamber does not correspond to the set value, food spoils or freezes.
- 🔌 The refrigerator does not respond at all to being plugged in, although the indicators are burning.
It is important to consider that similar symptoms can be observed with other breakdowns, for example, with a refrigerant leak. Therefore, before replacing a part, it is recommended to carry out simple diagnostics to rule out other options. Sometimes it is enough to simply “knock” on the regulator or turn it sharply to temporarily restore contact, which will confirm the hypothesis that the thermostat is faulty.
Necessary tools and preparation
To successfully replace the thermal relay, you will need a minimum set of tools, which is usually found in the arsenal of any home craftsman. The main tool will be a screwdriver, but its type may vary depending on the model of your refrigerator. Phillips screwdrivers are most often used, but in some models Indesit or Atlant there may be screws with a slot for a flat-head screwdriver.
You will also need a multimeter to check the continuity of the circuit and the new thermostat before installation. This will avoid a situation where you install a new part and it turns out to be defective. It will not be superfluous to prepare a container for collecting water if during disassembly you have to defrost the evaporator, and a flashlight to better illuminate the interior of the chamber.
- 🔧 A set of screwdrivers (phillips and flat) for removing panels and attaching the relay.
- 🔌 A multimeter or tester for checking the electrical circuit.
- 🧤 Gloves to protect hands from sharp edges and contamination.
- 📷 Smartphone for photographing the wiring diagram before disconnecting.
The preparatory stage also includes completely defrosting the refrigerator. Even if you change the thermostat in the refrigerator compartment, moisture may condense on the cold elements, and water contact with electrical contacts is unacceptable. Leave the refrigerator turned off for at least 12 hours so that all the ice melts and the water runs out.
☑️ Preparation for repair
Where the thermostat is located and how to get to it
The location of the thermostat depends on the design of the refrigerator and its model. In most modern units, such as Bosch or Liebherr, the thermostat is located inside the refrigeration chamber. It may be hidden behind a plastic panel on the ceiling of the chamber or located next to the lighting lamp. In older models, for example, some series Zil or Minsk, the regulator is often brought out and located on the top of the case.
If the thermostat is built-in, you will need to remove the protective cover to access it. It is usually secured with latches that need to be carefully pressed out, or with screws hidden under decorative plugs. Be careful when removing plastic panels, as the cold makes the plastic brittle and can easily crack if handled carelessly.
In two-chamber refrigerators with a system No Frost thermal sensors can be located directly on the evaporator, hidden behind the back wall of the freezer. In this case, access to them is significantly difficult and requires partial disassembly of the internal space of the freezer, including removal of the fan and air dampers.
⚠️ Attention: The design of refrigerators from different manufacturers may vary significantly. The mounting details and location of the components may not coincide with the description in the general instructions, so rely on a visual inspection of your unit.
After removing the protective panel, you will see the thermostat itself - this is a small box with wires and a capillary tube suitable for it (if the thermostat is mechanical). The capillary tube is a thin copper conductor that extends deep into the chamber or into the evaporator. It is she who senses the temperature and transmits pressure to the membrane inside the relay.
Removing the old thermostat
The dismantling process begins with disconnecting the electrical wires. As already mentioned, it is best to photograph the connection diagram in advance. The wires can be fastened using screw terminals or placed onto the terminals directly onto the thermal relay contacts. If screws are used, they must be carefully unscrewed, being careful not to drop them into hard-to-reach areas of the case.
The next step is to remove the sensitive element. In mechanical thermostats, this is a capillary tube, which is fixed to the evaporator or chamber wall using special clamps or clips. It must be released very carefully so as not to damage the thin tube, since breaking its tightness will lead to failure of the new thermostat immediately after installation.
The thermostat housing itself is usually attached to the refrigerator body or to the internal panel using screws or latches. After unscrewing the fasteners, carefully remove the device. In some models, for example, in refrigerators Stinol or Indesit, the thermostat may be enclosed in an additional plastic box, which will also need to be removed.
| Refrigerator type | Thermostat location | Complexity access | Dismantling features |
|---|---|---|---|
| Single chamber | Inside the chamber, near the lamp shade | Low | Removing one panel, free access to the capillary |
| Two-chamber (crying) | In the refrigerator compartment, under the top panel | Medium | You need to carefully remove the capillary tube |
| No Frost | Behind the back wall of the freezer cameras | High | Requires complete defrosting and removal of the fan |
| Built-in | Depends on the model, often at the top | Medium | Limited space for work |
When dismantling, pay attention to the condition of the wire insulation. If the braiding of the wires leading to the thermostat is cracked or melted, they must be replaced or the insulation restored before connecting a new part. Using electrical tape in low temperature conditions may be ineffective; it is better to use a heat-shrinkable tube.
Installation and connection of a new thermostat
Installation of a new one thermal relay is done in the reverse order of dismantling. First of all, fix the sensing element (capillary tube) in the same place where the old one was located. Use standard fasteners and clamps. Incorrect position of the tube will lead to incorrect temperature readings, and the refrigerator will work intermittently.
Then install the thermostat housing in place and secure it with fasteners. Make sure the device fits snugly and does not wobble. After this, you can begin connecting the electrical wires. Strictly follow the photograph or diagram you took earlier. Mixed-up wires can cause a short circuit or improper operation of the compressor.
If you are installing a universal thermostat, which is often used as a replacement for original parts, pay attention to the markings of the contacts. They are usually designated by numbers or letters (L, 1, 2, 4). Universal relays often come with instructions with a table of contact correspondence for different refrigerator models.
What to do if the wires are not the right length?
If the wires of the new thermostat are shorter, you can carefully extend them using copper wire of the same cross-section. The twists must be carefully soldered and insulated with heat shrink. However, it is better to try to find a part with a suitable length of wires in order to avoid unnecessary connections.
After connecting all the wires, visually check the reliability of the connections again. Nothing should be loose or touch moving parts, if any, in the installation area. Only after making sure that the assembly is correct can you proceed to testing.
Checking operation and setting
After installation is complete, turn on refrigerator connected to the network. In the first minutes of operation, listen carefully: the compressor should start after a while (or immediately if the temperature in the chamber is high). If the motor hums but does not start, or starts and immediately stalls, immediately turn off the appliance - there may be an error in connecting the wires.
Let the refrigerator run for several hours so that it reaches the temperature. Check the operation of the thermostat by turning the adjustment knob. When turning towards maximum cold, the compressor should work longer; when turning towards minimum, it should turn off more often. A characteristic click at the moment the motor is turned off or on indicates the activation of the contacts thermal relay.
- ✅ The compressor starts and operates cyclically (turns on and off).
- ✅ The set temperature is reached in the refrigerator compartment (check thermometer).
- ✅ There are no extraneous sounds, except for the usual hum of the motor.
- ✅ Condensation appears on the back wall of the refrigerator compartment (in drip systems), which periodically drains.
If the refrigerator operates continuously for more than 12 hours and does not turn off, the thermostat may need additional setting. On some models, there is an adjustment screw under the regulator handle, the rotation of which allows you to change the response temperature range. However, it is not recommended to touch it without special equipment and experience.
⚠️ Attention: If, after replacing the thermostat, the refrigerator begins to freeze weaker or stronger than before, do not rush to blame the new part. Perhaps the capillary tube is installed in the wrong place or tight contact with the evaporator is not ensured.
Frequently asked questions (FAQ)
Is it possible to replace a mechanical thermostat with an electronic one?
Theoretically, this is possible, but it requires a deep modification of the refrigerator control system. Electronic sensors operate on a different principle and require an electronic control unit, which is not available in models with a mechanical relay. It is easier and more reliable to find an analogue of a mechanical thermostat.
Why does the new thermostat click, but the compressor does not start?
This may indicate a malfunction of the compressor itself, the starting relay or a protective device. It is also possible that the thermostat is not connected correctly and the circuit to the motor is not closed. It is necessary to test the circuit with a multimeter.
How can you tell if the thermostat is working before installing it?
To check a mechanical thermostat, lower its sensitive tube into cold water with ice. After a few minutes, you should hear a click and the multimeter will show a short circuit across the contacts. If there is no click and the circuit does not close, the part is faulty.
Do you need to charge freon after replacing the thermal relay?
No, replacing the thermal relay does not affect the refrigerant circuit if you did not damage the capillary tube or evaporator during dismantling. The system remains sealed and refilling with freon is not required.
Where to buy an original thermostat for an old refrigerator?
Original spare parts for older models are often discontinued. In such cases, universal analogs are used that are suitable in size and electrical parameters. When purchasing, it is important to know the length of the capillary tube and the type of contacts.