Malfunction of the temperature control system often leads to food spoilage or the formation of an ice coat, and in most cases the culprit is the thermostat. Understanding how this unit works allows you not only to replace it, but also to carry out accurate diagnostics without calling a technician. Thermostat is a mechanical or electronic device that opens the electrical circuit when the specified cold parameters are reached.
Before proceeding with dismantling, it is necessary to completely turn off the power to the household appliance, since you will be working with live parts. Disassembling the refrigerator thermostat requires care, since the internal structure is sensitive to shocks and sudden movements. In this article, we will go into detail about the process of removing, checking and replacing the control.
It is important to note that the design of the regulator may vary depending on the manufacturer and type of compressor. Atlant, Indesit or Stinol often use similar mechanical models, while modern inverter systems may have electronic sensors. Your task is to determine the type of device before starting work.
The operating principle and design of the thermostat
A mechanical thermostat is a sealed system filled with gas or liquid that responds to changes in temperature. The main element is a bellows tube (capillary), which expands or contracts, acting on the contact group. It is this mechanism that ensures that the compressor's power supply circuit is broken.
Inside the housing there are electrical contacts that close under the action of the spring and pressure in the bellows. Stem the regulator transmits force from the control handle to the internal spring, changing the resistance force required to open the contacts. This allows the user to set the desired temperature.
Electronic thermostats work differently: they use thermistors, the resistance of which changes depending on heating or cooling. Such devices do not have moving mechanical parts in the sensing element, but require checking the control board. It is critically important to understand that mechanical thermostats are not dismountable in terms of repairing the internal hermetic damper - if the tightness of the bellows is broken, the assembly must only be completely replaced.
- 🔧 The bellows tube is the sensing element, reacting to cold.
- ⚡ Contact group - a mechanism for opening and closing the 220V circuit.
- 🎚️ Adjusting screw - allows you to calibrate the temperature range.
- 🧊 Insulating sleeve - protects contacts from condensation and moisture.
⚠️ Attention: The internal sealed capsule of the mechanical thermostat is filled with refrigerant under pressure. Under no circumstances should you try to drill into the body or damage the integrity of the bellows, as this may result in the release of a chemical substance and permanent failure of the part.
Required tools for dismantling
To successfully carry out the work, you will need a basic DIY kit. The main attention should be paid to tools for working with electrical equipment, since safety comes first. Multimeter will become your main assistant for checking the integrity of contacts.
Dismantling often requires access to hard-to-reach places, so a set of screwdrivers of different sizes and slot types is required. In some models of refrigerators, the fastenings may be hidden under decorative plugs, to remove which you will need a thin tip or knife.
☑️ Repair tools
Do not forget to prepare a container for defrosting if you need to bend it during disassembly evaporator You may also need electrical tape to mark the wires so as not to mix up the contacts during assembly. Passateno or other pliers will help to carefully pull out the latches.
Location of the thermostat in different models
The location of the temperature sensor directly depends on the design of the refrigerator compartment. In older models and devices with a weeping evaporator, the thermostat is often located inside the chamber. In modern systems No Frost access to it may be limited by plastic panels.
If the regulator handle is located on the outer panel of the door or the upper part of the body, then the mechanism itself is usually hidden behind a plastic cover. In two-chamber refrigerators with one compressor, the thermostat most often serves the fridge compartment, and the freezer operates on the residual principle or has its own separate sensor.
To find the installation location, carefully inspect the interior space. The capillary tube can be inserted into a special sleeve on the rear wall or secured with a clip to the evaporator. In some cases, for example, brand Beko or LG, it may be hidden behind a decorative strip on the ceiling of the chamber.
Step-by-step instructions for disassembling the unit
The process of removing the thermostat begins with removing the adjustment knob. It is usually simply removed by hand, but if it is tight, you can carefully pry it off with a flat screwdriver wrapped in fabric so as not to damage the plastic. After removing the handle, access to the fastening elements opens.
Next, you need to dismantle the protective casing or plastic cover, which is held on by latches or screws. Be careful: the plastic on older refrigerators becomes brittle and can crack if given a sudden tug. If the screws are hidden, look for plugs near the handle.
After removing the housing, you will see the thermostat itself, mounted on a metal plate. Disconnect the capillary tube from the evaporator, remembering or photographing the route of its installation. Then unscrew the mounting screws of the thermostat housing itself.
- 📸 Take a photo of the wire connection diagram before disconnecting.
- 🧤 Use gloves to avoid leaving greasy marks on the contacts.
- 🔌 Disconnect the wire chips by holding the connector body, not by themselves wires.
- 🧊 Carefully pull out the sensing tube so as not to damage the evaporator.
⚠️ Attention: When removing the capillary tube from the evaporator sleeve, do not use excessive force. The tube is very thin and can easily be cut or deformed, which will make the new thermostat inoperable.
Diagnostics and checking contacts
After removing the device, you need to check its functionality. To do this, use a multimeter switched to continuity or resistance measurement mode. There should be no traces of soot or oxidation on the contacts, which may interfere with the passage of current.
Checking is carried out by shorting the probes to the contact terminals. In normal condition (at room temperature), the contacts of the mechanical thermostat should be closed. If the device shows a break, it means that the contacts are burnt or the mechanism is jammed.
For a complete diagnosis, you can place the sensitive tube in a container with cold water (about 0°C) or apply ice to it. After a few minutes the contacts should open and the multimeter will show infinite resistance. If this does not happen, the thermostat is faulty.
| Condition | Environment temperature | Multimeter readings | Action |
|---|---|---|---|
| Normal | +20°C | 0 Ohm (Sound) | Contacts closed |
| Normal | 0°C (Ice) | ∞ (No sound) | Contacts open |
| Fault | +20°C | ∞ (No sound) | Replace thermostat |
| Fault | 0°C (Ice) | 0 Ohm (Sound) | Replace the thermostat |
Is it possible to restore burnt contacts?
In theory, the contacts can be cleaned with a file or fine sandpaper. However, this measure is temporary: sparking during switching will continue, and after a short time the contacts will burn out or weld again. In addition, when disassembling the sealed housing, the calibration of the springs is disrupted, and the thermostat will not work correctly.
Replacement and features of installing a new regulator
Installation of a new thermostat is carried out in the reverse order. The main requirement is exact compliance with the markings. Even if the dimensions are the same, the characteristics (on/off temperature, capillary length) may differ. Marking usually applied to the metal body.
When installing the capillary tube, make sure that it fits tightly to the evaporator or is correctly inserted into the sleeve. Poor contact of the tube with the cooled surface will lead to incorrect operation of the refrigerator: it will either not freeze or work without stopping.
After assembling all the plastic elements and connecting the wires, turn on the refrigerator. For the first few operating cycles, control the temperature manually, as additional adjustment may be required using the screw located on the thermostat housing.
Frequently asked questions (FAQ)
Is it possible to install thermostat from another manufacturer?
This is only possible if the mounting dimensions, capillary tube length and, most importantly, temperature characteristics match. However, it is better to look for an original spare part or a complete analogue recommended by the refrigerator manufacturer in order to avoid problems with the cycling of the compressor.
Why does the refrigerator not turn off after replacing the thermostat?
Most likely, the capillary tube is not immersed deep enough in the evaporator sleeve or is not pressed well against it. Also, the cause may be incorrect setting of the adjusting screw or installation of a thermostat with an inappropriate temperature range.
How to determine that the problem is in the thermostat and not in the compressor?
If when you turn the control knob you do not hear a characteristic click, and the compressor is silent, and the light inside the chamber is on, there is a high probability of a thermostat malfunction. If there is a click, but the compressor does not start (even if the start relay is working), the problem may be in the engine itself.
Is it necessary to defrost the refrigerator before replacing it?
Yes, complete defrosting is required. Ice can interfere with access to the fasteners, and moisture inside the camera is dangerous when working with electrical contacts. In addition, thawed ice will allow you to carefully remove the capillary tube from the icy sleeve.