A sudden stop in the operation of the refrigerator compartment or, conversely, its excessive freezing often indicates a failure in the temperature control system. In most household models, this process is controlled by thermal relay, also known as a thermostat or temperature sensor. Understanding where exactly this unit is located is the first step towards self-diagnosis or qualified repair.
The location of the element directly depends on the design of the unit, year of manufacture and manufacturer. In older mechanical-type models, it can often be found outside or under a simple plastic cover, while in modern systems No Frost and electronic control boards, access to the sensor can be significantly limited. Precise localization of the thermal relay is possible only after removing the rear protective panel inside the camera or dismantling the lighting lamp, depending on the specific modification.
Before you begin disassembling, you must clearly understand the operating principle of the device. The thermal relay closes or opens the electrical circuit of the compressor depending on the temperature inside the chamber. If you notice that the refrigerator runs intermittently or does not turn on at all, the problem may lie in this component. The following text will help you navigate your search and avoid common diagnostic mistakes.
Operation principle and types of thermal relays
A thermal relay is an electromechanical or electronic switch that responds to changes in the temperature of the working environment. Classic models use a bellows tube filled with refrigerant that contracts or expands when cooled or heated. This physical effect is transmitted to the contacts, opening the compressor power circuit when the specified temperature is reached.
Modern refrigerators are increasingly equipped with electronic temperature sensors that do not have moving mechanical parts. Such devices, often called thermistors, change their electrical resistance depending on temperature. The signal from them is sent to the main control unit, which already makes the decision to start or stop the engine. You can distinguish them by their appearance: mechanical relays are usually larger and have an adjusting screw.
⚠️ Attention: An attempt to replace a mechanical thermal relay with an electronic sensor (or vice versa) without resoldering the circuit and changing the firmware of the control unit will lead to irreversible failure of the equipment. Use only original spare parts or their complete analogues.
It is important to understand the difference between the main thermostat and additional defrost sensors. The main regulator controls the overall temperature in the chamber, while defrost sensors monitor the condition of the evaporator. Their location also differs, and they should not be confused when diagnosing. To accurately determine the type of your device, it is best to refer to the technical documentation of the model.
Localization in models with mechanical control
In old-style refrigerators, such as classic Atlant, Biryusa or early models Indesit, the thermal relay is most often located inside the fridge compartment. This makes it easier to access since it does not require complete disassembly of the case. Usually the element is hidden behind a plastic cover or integrated into the temperature control unit.
The standard placement location is the upper part of the refrigerator compartment, often in the corner. The temperature regulator in the form of a rotary knob or a scale with numbers is an external manifestation of the internal mechanism of the thermostat. To get to the electrical component itself, you need to carefully remove this handle and unscrew the mounting screws underneath.
- 🔍 Remove the plastic regulator handle by pulling it towards you (sometimes you need to pry it off with a thin screwdriver).
- 🔍 Unscrew the screws hidden under the decorative panel or directly under handle.
- 🔍 Carefully move the plastic case to see the bellows tube and contact group.
- 🔍 Check the tight fit of the tube to the evaporator - it should be secured with a clip.
In some cases, the thermal relay can be moved outside the chamber, for example, in engine compartment or on the rear wall of the housing. This is typical for industrial models or specific series of household appliances. If inside the chamber under the adjustment knob you found only wires going to the light bulb, then the sensor itself is located in a different place, probably next to the evaporator.
Location in No Frost systems and electronic boards
Refrigerators operating using technology No Frosthave a more complex sensor system. Here the thermostat (or thermistor) is often located not in the main chamber, but in the air circulation area or directly on the evaporator, hidden behind the rear panel of the freezer compartment. Access to it is difficult and requires partial disassembly.
In models with electronic control (LG, Samsung, Bosch), temperature sensors are small plastic elements on wires. They can be built into the air ducts or mounted on plastic holders inside the chamber. To replace them, it is often necessary to remove the back wall of the refrigerator or freezer, which means defrosting the unit.
Key areas for searching for sensors in modern systems:
- ❄️ Behind the rear plastic panel in the freezer (evaporator area).
- ❄️ In the top parts of the refrigerator compartment, next to the cold air supply channel.
- ❄️ In the niche for the lighting lamp (in some models the defrost sensor is hidden there).
- ❄️ Under the bottom of the chamber, if we are talking about the air temperature sensor below.
When working with electronic systems, it is important to be careful. Plastic that has been exposed to low temperatures for a long time becomes brittle. Sudden movements when removing panels can lead to breakage of fasteners or damage to the sensors themselves. Before starting work, it is recommended to let the refrigerator stand unfrozen for several hours.
Symptoms of a thermal relay malfunction
Understanding where the thermal relay is located is useless without the ability to diagnose its failure. The malfunction of this unit is manifested by characteristic symptoms that are difficult to confuse with other problems. If the refrigerator hums but does not cool, or, conversely, turns food into ice blocks, this element is the first to be suspected.
One of the most obvious signs is the absence of a characteristic click when changing the position of the temperature regulator. In a working mechanical relay, when turning the knob from minimum to maximum, a clear sound of contacts opening or closing should be heard. If there is no click, and the tester shows an open or short circuit, the part requires replacement.
Other symptoms include:
- 🔥 The compressor runs continuously without turning off, the temperature in the chamber drops below normal.
- 🔥 The refrigerator does not turn on at all, although the light is on and there is voltage in the network.
- 🔥 Frequent switching on and off of the motor (clocking) that does not correspond to the settings.
- 🔥 Freezing of “fur coat” or ice on the back wall during normal operation.
It is worth noting that similar symptoms can occur if there is a freon leak or a malfunction of the start relay compressor. Therefore, visual inspection and checking the integrity of the bellows tube (for mechanical damage) are mandatory diagnostic steps before purchasing a new part.
Instructions for accessing and replacing the component
The process of replacing a thermal relay requires basic skills in working with power tools and observing safety precautions. The first and most important rule is to completely disconnect the refrigerator from the electrical network. Any manipulations with live wiring are unacceptable and life-threatening.
After disconnection, it is necessary to provide access to the node. Depending on the model, remove the inner panel, lamp shade, or back cover. If the thermostat is mechanical, carefully disconnect the bellows tube from the evaporator, remembering or photographing the location of its attachment. Then disconnect the wires, having previously marked them with a marker so as not to be confused during assembly.
☑️ Checklist before replacing the thermal relay
Installing the new element is done in the reverse order. It is important to ensure tight contact of the bellows tube with the surface of the evaporator, if the model requires it. For electronic sensors, the main thing is to carefully insert the connector until there is a characteristic click and lay the wires correctly so that they do not fall into the fan rotation zone.
After assembly, do not rush to load products. Turn on the refrigerator idle and check its operation for several hours. Check if it pauses and reaches the required temperature. If the cycle works, the repair can be considered successful.
Table of common installation locations by brand
Different manufacturers use their own standards for the layout of components. Below is a summary table that will help you navigate the search for thermostats for the most popular brands of refrigerators. Remember that within one brand there may be different series with different designs.
| Brand | Type of control | Typical location | Access features |
|---|---|---|---|
| Atlant | Mechanical | Inside the camera, top left | Removing the handle and screws under the cover |
| Indesit | Mechanical/Electronic | Lamp shade or inside the camera | Requires dismantling of the ceiling lamp |
| Samsung | Electronic | Behind the rear panel (No Frost) | Full defrosting and removing the panel |
| Bosch | Electronic | Air duct or evaporator | Difficult access, requires a Torx tool |
| LG | Electronic | In the fan niche | Access through the freezer compartment |
⚠️ Attention: Design features of models may vary depending on the year of manufacture. The locations indicated in the table are the most probable, but not 100% guaranteed for all modifications.
Precautions and expert advice
Working with refrigeration equipment involves risks associated not only with electricity, but also with the fragility of materials. Plastic elements lose their elasticity at low temperatures. If you are carrying out repairs in winter in an unheated room, allow the parts to warm up to room temperature before manipulation.
When replacing a mechanical thermal relay, ensure the integrity of the bellows tube. Damage to it will cause sensitive gas to leak and the new relay will immediately fail. Do not bend the tube at an acute angle or apply excessive force to it. The bending radius should be smooth.
Another important aspect is tightness. If you removed the panel covering the evaporator, make sure that the rubber seal around the perimeter lies flat and does not have any creases. Violation of the tightness will lead to moisture getting inside the system, ice formation and, as a result, fan breakdown or channel clogging.
If after replacing the thermal relay the problem does not disappear, it may not be the sensor. The malfunction may be hidden in the control module, start relay or the compressor itself. In such cases, self-repair may become more expensive than a professional one, so it is worth considering calling a specialist for in-depth diagnostics.
Frequently asked questions (FAQ)
Is it possible to repair the thermal relay yourself or just replace it?
In 95% of cases, the thermal relay must only be replaced. This is a sealed unit, and violation of its integrity during repairs leads to the loss of the sensitive element. Attempts to adjust the screws on the body of a mechanical relay are possible, but are temporary and require calibration equipment.
Why does the refrigerator not turn off after replacing the thermal relay?
There may be several reasons: the analogue is incorrectly selected (the temperature range is not suitable), the bellows tube does not fit tightly to the evaporator, or the problem is not in the thermal relay at all (freon leak, compressor malfunction). It is also worth checking whether the contacts on the relay itself are stuck.
How to check a thermal relay with a multimeter?
You need to remove the relay, disconnect the wires and put the multimeter in dial mode. At room temperature the contacts should ring (if it is a normally closed contact). When the sensor is placed in the cold (for example, in a freezer for 10-15 minutes), the circuit should open and the sound disappear.
Where is the thermostat located in a two-chamber refrigerator with one compressor?
Usually the main thermostat controls the temperature in the refrigerator compartment, and a defrost sensor or a second thermostat may be located in the freezer (in older models). In systems No Frost with one compressor, control often comes from one electronic unit that collects data from several sensors.
How much does it cost to replace a thermal relay, taking into account the work?
The cost consists of the price of the spare part (from 500 to 2000 rubles depending on the model) and the work of the technician. At service centers, travel and diagnostics may be paid separately. Self-replacement saves the budget, but requires tools and time.