Thermostat malfunction is one of the most common reasons why a household refrigerator stops maintaining the set temperature. If the compressor runs without stopping or, conversely, does not start at all, and it is warm inside the chamber or everything is frozen to the point of ice, there is a high probability of failure of this particular unit. Replacing a part yourself is quite possible for a person with basic skills in working with a tool, but requires strict adherence to safety precautions and an understanding of the electrical circuit.
Before proceeding with the dismantling of the old device, it is necessary to clearly understand that a thermostat is not just a switch, but a complex mechanical device that responds to changes in the temperature of the refrigerant or air. Incorrect connection or ignoring installation nuances can lead to a short circuit or failure of the compressor. In this article we will analyze all stages of the process, from diagnostics to the final launch of the system.
It is important to note that the design of thermostats may differ depending on the manufacturer of the refrigerator, be it Indesit, Atlant or Bosch. However, the general principle of operation and sequence of actions remain similar. The main thing is not to rush and carefully mark the wires before disconnecting them to avoid confusion during assembly.
Principle of operation and design of the thermostat
The thermostat is a sealed system filled with a temperature-sensitive gas (freon), which is located in a capillary tube and bellows. When the temperature inside the refrigeration chamber changes, the gas expands or contracts, affecting the bellows membrane. This mechanical movement closes or opens electrical contacts, starting or stopping the compressor.
Located inside the housing lever mechanism and contact group. It is the contacts that transmit voltage to the motor starting relay. Modern models may have additional features such as automatic defrost or evaporator temperature control. Understanding this mechanism helps diagnose the problem: if gas has escaped through a microcrack, the thermostat will stop responding to climate changes in the chamber.
⚠️ Attention: The capillary tube of the thermostat is very thin and sensitive to creases. When installing a new regulator, avoid sharp bends in the tube, as this may disrupt gas circulation and lead to false temperature readings.
There are two main types of thermostats: with an external capillary tube (for single-chamber refrigerators and freezers) and with a built-in sensing element (for double-chamber models). In the first case, the tube is attached to the evaporator, in the second, the sensor is immersed directly in the air flow inside the chamber. An error in choosing the type of device will lead to incorrect operation of the entire system.
Why do thermostats fail?
The main reason is the natural wear of the contact group. Over time, carbon deposits form on the contacts, they begin to spark and stick. It is also possible for the bellows to depressurize, which makes the device completely inoperable.
Diagnostics of the malfunction before replacement
Before buying a new part and disassembling the unit, you need to make sure that the problem lies in the thermostat. Symptoms may be similar to a breakdown of the start relay or the compressor itself. Primary diagnostics are carried out by visual inspection and checking the system's response to changing settings.
If the refrigerator hums, but there is no cold, or, conversely, freezes food to the point of stone, try turning the control knob. The absence of a characteristic click when turning from the extreme position to the opposite often indicates a mechanical breakdown inside the housing. However, for accurate diagnosis, the use of a multimeter is required.
- 🔍 Continuity check: Test the thermostat contacts with a multimeter in ohmmeter mode. At room temperature, the circuit should be closed (resistance close to zero).
- ❄️ Cold test: Place the sensing element in the freezer for 15 minutes. After cooling, the contacts should open (infinity resistance), which indicates serviceability.
- 🔌 Visual inspection: Check the integrity of the capillary tube and the absence of traces of oxidation or burning on the connection terminals.
Sometimes the cause of failure is not the device itself, but an oxidized contact or a wire break at the connection point. Carefully inspect the wiring going to the thermostat. If there is no visual damage, and continuity shows an open circuit at normal temperature, the part must be replaced.
Necessary tools and preparation for work
To successfully replace the thermostat, you will need a minimum set of tools, which is usually in the arsenal of a home craftsman. The main requirement is safety and accuracy, since the work is carried out with electricity and plastic elements that are easily damaged.
Be sure to turn off the power to the refrigerator before starting any work. Unplug the plug and gain access to the back wall or interior of the chamber where the assembly is located. Do not attempt to carry out live repairs, even if it seems to you that you are isolated from live parts.
☑️ Tools for replacement
Prepare the workplace: it should be well lit. You may also need a hair dryer to carefully remove plastic plugs if they are stuck, or WD-40 to treat soured screws. Take a photo of the connection diagram of the old thermostat in advance, this will become your main cheat sheet.
Step-by-step instructions: dismantling the old thermostat
The process of removing the device depends on the model of the refrigerator. In most cases, the thermostat is hidden under a plastic panel inside the chamber or behind a casing on the back wall. Proceed sequentially, fixing each stage so that no questions arise during assembly.
First remove the temperature control knob. It may be a tight fit, so use a flat head screwdriver and pry it out carefully to avoid breaking the plastic. Then remove the mounting screws holding the thermostat housing in place. In some models Stinol or Indesit access is through the lampshade.
After gaining access to the electrical part, carefully inspect the color markings of the wires. Before disconnecting, be sure to mark each wire and corresponding terminal with a marker. This is a critical point, as wire colors may differ from standard designs in different batches.
⚠️ Caution: Never pull on wires to disconnect them. Handle only the connector or terminal itself. A sudden force can break the wire inside the insulation, creating a hidden problem that will be difficult to find later.
Carefully remove the capillary tube from its seat. It can be secured with a bracket or simply inserted into the hole. If the tube is stuck to the evaporator, do not use force - it is better to slightly warm the connection with a hairdryer or treat it with a defrost.
Connection diagram and installation of a new regulator
Installation of a new thermostat is carried out in the reverse order of dismantling. The most difficult thing here is to connect the wires to the terminals correctly. Standard markings usually include the following colors, but always check the instructions for the specific model.
| Contact on the thermostat | Wire color (standard) | Function | Purpose |
|---|---|---|---|
| 3 | Red / Orange | Phase (L) | Power supply |
| 4 | Black / Brown | Compressor | Start motor |
| 6 | Yellow / Green | Grounding | Housing safety |
It is important to understand that the connection diagram for the refrigerator thermostat Atlant may differ from the diagram Liebherr. For example, some models have a contact for a light bulb or fan. If you are installing a universal thermostat, carefully study the diagram supplied with it.
After connecting the wires, make sure that they are securely fixed and do not dangle. Vibration from a running compressor can loosen a poor connection, leading to sparking and heating. Lay the capillary tube along the same path where the old one lay, avoiding sharp metal edges.
Secure the thermostat housing with screws and install the decorative panel. Make sure that the control knob rotates freely and does not touch the walls of the niche. Only after complete assembly can you begin testing.
Checking performance and setting
After turning on the refrigerator, listen to the operation of the compressor. It should start in a few seconds or minutes (depending on protection). If the motor hums but does not start, immediately turn off the power - the phases may be reversed or the relay is stuck.
Let the refrigerator run idle for several hours. Check the temperature in the chamber using an external thermometer. The adjustment is made experimentally: if the temperature is too high, turn the knob to a higher value, if it is too low, reduce it.
- 🌡️ Cycling: The compressor should be turned off periodically. If it runs continuously for more than an hour, the thermostat may not sense the cold.
- 🧊 Frost: Even distribution of frost on the back wall indicates normal operation of the system.
- 🔊 Sounds: Thermostat clicks should be heard when it reaches set temperature.
⚠️ Attention: Technical characteristics of refrigerators may vary depending on the year of manufacture and modification. Always check the parameters of the new thermostat (temperature range, capillary length) with the original part before installation.
Frequently asked questions (FAQ)
Is it possible to install a thermostat with a different marking?
Yes, if the overall dimensions and capillary length are the same tubes and temperature range. However, it is better to look for a complete analogue by catalog number to avoid problems with seats and settings.
Why does the refrigerator not turn off after replacement?
Perhaps the wires are connected incorrectly, the capillary tube does not fit tightly to the evaporator, or the new thermostat has a different temperature range. It is also worth checking the tightness of the refrigerator system.
Is it necessary to defrost the refrigerator before replacing?
Yes, this is a mandatory requirement. Water that gets on the electrical contacts or inside the new thermostat can cause short circuits or corrosion. Let the unit dry completely.
How to determine that it is the thermostat that is broken and not the relay?
Short the wires going to the thermostat, bypassing it. If the compressor starts and runs, the thermostat is faulty. If the motor hums but stops, the problem is in the start relay or compressor.