A sudden stop of the compressor or, conversely, its continuous operation often indicates a failure of one of the key elements of the temperature control system. Thermostat (or thermostat) is a mechanical or electronic device that closes and opens an electrical circuit depending on the temperature inside the chambers. It is he who “tells” the motor when to start the cooling cycle and when to rest.
If you notice that the food in the main chamber has begun to thaw, and in the freezer, on the contrary, excessive ice has formed, or the unit has completely stopped responding to turns of the adjustment knob, the problem most likely lies in the sensor. Replacing this part is one of the most accessible procedures in self-repair household appliances, which does not require deep knowledge of electronics, but requires care and adherence to safety precautions.
In this article we will analyze in detail the algorithm for diagnostics and replacement thermostat. You will learn how to correctly remove the old element, what to look for when choosing an analogue and how to avoid common mistakes that can lead to repeated breakdown or damage to other components of the refrigerator.
Symptoms of malfunction and initial diagnosis
Before disassembling the refrigerator, you need to make sure that the problem is real in the thermostat, and not in a freon leak or compressor malfunction. The most striking symptom is when the motor-compressor either does not turn on at all (the chamber is warm, there is no light, there is silence), or it works non-stop, freezing everything to the point of stone. In normal operation mode on and off cycle should alternate with a certain frequency.
For an initial check, you can use a simple “closing” method. To do this, you need to get to the thermostat, remove the wires from its contacts and connect them directly to each other (after disconnecting the refrigerator from the network!). If, after plugging into the socket, the compressor starts working, it means that the circuit is working properly, and the culprit of the silence is the temperature sensor temperature sensor.
⚠️ Attention: Before any manipulations with electrical wires, be sure to disconnect the refrigerator from the power supply. Working under 220V voltage is deadly to life.
Another sign is an incorrect reaction to turning the knob. If you turn the regulator from minimum to maximum, but there is no characteristic click (in mechanical models), or there is a click, but the compressor does not respond, this confirms the need for replacement. It is also worth checking the condition of the capillary tube: there should be no cracks or signs of oxidation.
Necessary tools and preparation for work
For successful repairs, you do not need complex professional tools, but having a basic set is mandatory. The main time will be taken not by the replacement itself, but by dismantling the panels and gaining access to the assembly, which is often hidden in hard-to-reach places of the case or inside the camera.
You will need the following tools:
- 🔧 Screwdrivers: Phillips and flat (different sizes for different screws).
- 🔧 Pliers or pliers (for gripping terminals).
- 🔧 Multimeter (tester) for continuity testing.
- 🔧 Knife or scalpel (for careful removal of insulation, if necessary).
- 🔧 Electrical tape or heat shrink for insulating connections.
Also prepare a container for defrosting in advance if the process requires complete defrosting of the unit. Although replacing the thermostat often does not require a complete defrost, having some rags and a basin is never a bad idea. It is important to ensure good lighting of the work area, since the depths of the niches of the refrigerator are usually dark.
Removing the old thermostat
The location of the thermostat depends on the model of the refrigerator. In older models (for example, Atlant, Biryusa, old Indesit) it is often located inside the refrigerator compartment, in a plastic box along with or next to the light bulb. In modern models with the system No Frost the thermostat can be moved outside the chambers, into a special compartment on the back wall or in the upper part of the case.
The dismantling process begins with the removal of decorative panels. If the regulator is inside: carefully pry up the plastic handle of the regulator, unscrew the screws securing the lamp shade or the thermostat housing itself. Be careful with plastic latches - they become brittle in the cold and easily break if handled carelessly.
If the thermostat is located outside (in the “head” of the refrigerator or behind the back panel):
- Remove the top cover of the refrigerator (usually held on by two screws at the back and latches at the front).
- Find a plastic box into which the capillary tube goes.
- Unscrew the fastening screw that secures the thermostat housing.
- Carefully pull out the housing, trying not to damage the capillary tube, which may be glued to the evaporator inside the chamber.
⚠️ Attention: The capillary tube of the thermostat is very thin and sensitive to mechanical damage. Under no circumstances bend it at an acute angle or pull it with force. Damage to the tube will lead to leakage of sensitive gas, and the new thermostat will have to be thrown away.
☑️ Dismantling procedure
Comparison of characteristics and selection of an analogue
Thermostats are not universal devices. Each model is designed for a specific temperature range and has a specific capillary tube length. Installing an unsuitable sensor will result in the refrigerator either not turning off or not being able to reach the desired temperature.
When looking for a replacement, pay attention to the markings. There is always a code on the case (for example, K-50, K-59, TAM-133). The numbers at the end often indicate the length of the capillary tube in centimeters. If you install a thermostat with a 0.6 m tube instead of 2.5 m, it simply will not reach the desired zone in the evaporator.
Below is a table of popular analogues for various brands:
| Original (Marking) | Suitable analogues | Capillary tube length | Application |
|---|---|---|---|
| Danfoss K-50 | TAM-133, Ranco K50 | 0.75 m - 2.5 m | Single-chamber refrigerators |
| Danfoss K-59 | TAM-145, Ranco K59 | 0.75 m - 3.0 m | Two-chamber (upper cold) |
| Thermo 112.201 | K-57, K-58 | 0.7 m - 1.3 m | Chest freezers |
| Ortiz 6330 | K-52, K-56 | 1.0 m - 2.0 m | Refrigerators with No. Frost |
It is also important to consider the presence of a third contact (often marked with a red dot or number 3). It is responsible for the hazard warning light or indication. If this contact is not used in your model, you can use a thermostat without it, but if it is, it is better to choose a complete analogue so as not to interfere with the functionality of the indication.
Installation of a new thermostat and connection
Installation of a new element is carried out in the reverse order of dismantling. The most difficult thing here is to position the capillary tube correctly. It should be fixed in the same place and with the same tightness to the evaporator as the old one. Often, special clamps or aluminum plates are used for fixation.
Connecting wires requires care. Use a photo you took earlier. If there are three wires, and the new thermostat also has three contacts, just move them by color. If there are more contacts (for example, 4), and the old one had 3, the extra one (usually for an emergency signal) can be left free by insulating its end.
Action algorithm:
- 🔌 Insert the capillary tube into the mounting hole until it stops, but without fanaticism.
- 🔌 Secure the thermostat housing with a screw.
- 🔌 Place the terminals on the contacts, ensuring a tight fit (if the terminals are oxidized, clean them).
- 🔌 Make sure the wires do not touch moving parts or hot elements (if there are any nearby).
Installation nuances in No Frost refrigerators
In No Frost systems, the thermostat often controls the temperature of the evaporator, rather than the air in the chamber. It is important to ensure that the sensitive bulb is pressed tightly to the surface of the evaporator through heat-conducting paste or a special gasket. Poor contact will lead to sensor “lies” and incorrect defrost cycles.
Checking performance after replacement
After assembling all the panels and connecting the refrigerator to the network, do not expect an instant result. The compressor may take time to start, especially if a protection relay has been used. In the first 15-20 minutes, listen to the unit: the hum of the engine and the characteristic gurgling of freon should appear.
After 30-40 minutes, check the temperature in the chambers. If you installed a new thermostat, you may need to make some minor adjustments. Rotate the knob to different positions, listening for clicks. The motor should turn off when the set temperature is reached and turn on when it rises.
Pay attention to the duration of the cycles. If your refrigerator runs for too long without a break, the thermostat may be set too low or the capillary tube may not be deep enough into the cold zone. In this case, re-disassemble and adjust the position of the tube.
Frequently asked questions (FAQ)
Can an old thermostat be repaired? and not change it?
In 99% of cases, repair is impossible. The thermostat is a sealed system filled with freon gas. If the gas has evaporated or the membrane has lost elasticity, it is impossible to restore factory settings at home. It’s easier and cheaper to buy a new one.
Why does the new thermostat click, but the compressor does not start?
This may indicate a problem not with the thermostat, but with the compressor start relay or the motor itself. Also check whether the terminals are tightly seated on the contacts of the new sensor - a bad contact does not allow current to pass through.
What is the difference between a thermostat with a red dot and a regular one?
The red dot (or number 3) indicates a contact for an alarm or defrost indicator. If this wire was not used in your circuit, you can install a thermostat without such markings. If there was a wire, you need a similar one.
How to understand that the capillary tube is too long?
If the tube is much longer than the original, it can be carefully rolled into a ring (at least 3-4 cm in diameter) and placed in the free space behind the back wall or in a niche. The main thing is not to break it.