Failure of the temperature control system - one of the most common reasons for calling service, but in many cases you can do the replacement yourself. Thermostat is a key element that controls the operation of the compressor, and its incorrect operation leads to either insufficient cooling or complete defrosting of food. Understanding the principle of operation of this unit and the sequence of actions when replacing it will allow you to save significant money on calling a technician.
Before proceeding with disassembly, you need to make sure that the problem lies precisely in the sensor, and not in a freon leak or a motor malfunction. Thermoregulator (often called a thermostat) is an electromechanical device that opens the electrical circuit when the set temperature inside the chamber is reached. If you observe that the compressor is running non-stop or, conversely, does not turn on at all when the start relay is working, there is a high probability that this particular component needs to be replaced.
Safety is the main priority when working with household appliances. Before starting any manipulations with electrical components, make sure that the device is completely disconnected from the network. The voltage of 220 volts is deadly for humans, so checking the absence of current on the contacts with a multimeter mandatory before touching the wires. Also prepare the workplace: it should be well lit, and all tools (screwdrivers, pliers, multimeter) should be in working order and at hand.
Diagnostics of a thermostat malfunction
The first step should always be a thorough diagnosis in order to exclude false conclusions. Users often confuse a broken thermostat with defrost system problems or a refrigerant leak. If the refrigerator is humming, but there is no cold, or it is silent, although it is warm in the chamber, these are direct indications for checking the control circuit. In some electronically controlled models, such as Electrolux or Bosch, a sensor malfunction may be displayed as an error code on the display, which greatly simplifies troubleshooting.
For mechanical thermostats, there is a simple “short circuit” test method. If you close the contacts that go to the thermostat and the compressor starts, it means that the motor itself is working, but the problem is in the control circuit. However, you should be careful: during such testing, the refrigerator will work continuously without turning off, which can lead to freezing of food or freezing of the evaporator if left in this state for a long time.
- 🔍 The compressor does not turn on, but the light inside the chamber is on - a sign of an open thermostat circuit.
- ❄️ The unit operates without breaks, a “fur coat” forms on the back wall - the thermostat contacts are “stuck” in the closed state.
- 🔌 There is no voltage on the contacts when dialing with a multimeter in a cold state - the device has failed.
It is important to understand that different models of refrigerators may have different response characteristics. For example, freezer compartments use devices with lower shutdown thresholds than refrigerator compartments. Using an analogue that is not suitable for its parameters can lead to incorrect operation of the entire system.
Preparation of tools and selection of a new thermostat
The success of the repair directly depends on the correctness of the selected spare part. Thermostats are not universal parts: they differ in the length of the capillary tube, operating temperature range, mounting method and contact arrangement. When purchasing a new part, be sure to write off the markings from the old device. The most common models from manufacturers Klixon, Tam, Orbel and Thermo.
In addition to the thermostat itself, you will need a standard home handyman kit. The main tool will be a Phillips and flathead screwdriver, since the mounting screws can be of different types. To check the integrity of circuits, a multimeter set to continuity mode is indispensable. You may also need needle-nose pliers for working in hard-to-reach places and electrical tape or heat shrink to insulate connections.
Pay attention to the length of the capillary tube of the new thermostat. If it is too long, it can be carefully laid in rings inside the housing, but in no case should the tube be bent or shortened, since there is a sensitive liquid or gas inside, the change in volume of which controls the contacts. Damage to the tube will make the device inoperable.
Removing the old thermostat
The process of removing the old device requires care, especially when working with plastic elements of the refrigerator interior. In modern models, the thermostat is often hidden behind a plastic panel inside the chamber or located in the upper part of the housing outside. In refrigerators Indesit i Ariston the regulator is usually located inside the refrigerator compartment under the lampshade.
Before removing the plastic cover, wait until the plastic has warmed to room temperature if you have just defrosted the refrigerator. Cold plastic becomes brittle and can easily crack under careless pressure. Remove the temperature control knob if it protrudes outward and unscrew the mounting screws.
⚠️ Attention: The capillary tube of the thermostat is very thin and sensitive to creases. When removing the old sensor, do not pull the wire sharply so as not to damage the evaporator or other internal elements of the refrigerator.
After gaining access to the mechanism itself, take a photo of the wiring diagram. The color coding of the wires may not comply with the standards, and relying on memory in this case is risky. Disconnect the terminals by gently pulling on them, not on the wires themselves. If the terminals are oxidized, it is better to clean them before installing a new device.
☑️ Removal procedure
Connection diagram and installation of a new device
Installation of a new thermostat is carried out in the reverse order of dismantling. The main rule is to strictly follow the color coding of the wires that you recorded earlier. In most cases, the brown or black wire is the phase coming from the mains, and other colors (yellow, green, red) lead to the compressor or lamp. An error in the connection can lead to a short circuit or malfunction of the unit
The capillary tube of the new thermostat must be secured in the same place where the old one was located. Usually it is attached with a special clip to the evaporator or inserted into the technological hole. The accuracy of temperature measurement depends on the position of the sensing element. If the tube dangles in the air of the chamber, the refrigerator will not work correctly, turning on and off frequently.
In models with an air damper (for example, some series LG or Samsung), the thermostat can control not only the compressor, but also the cold air supply damper. In this case, the number of contacts will be greater, and the connection diagram will become more complicated. Here it is especially important not to confuse the control circuits of the damper motor and the main compressor.
| Refrigerator type | Thermostat location | Installation features |
|---|---|---|
| Single chamber (Atlant, Biryusa) | Inside the chamber, under the ceiling | The tube is fixed to the evaporator |
| Two-chamber (Indesit, Ariston) | Inside the refrigeration chamber | Requires removal of the top panel |
| No Frost (Samsung, LG) | Often outside, at the top of the case | Access through the back cover or ceiling |
| Built-in models | Behind the door front panel | Difficult access, requires removing the door |
After physically attaching the device and connecting the wires, reassemble the case in the reverse order. Make sure all latches are in place and no wires are caught under moving parts or sharp plastic edges. Securely fasten the temperature control knob.
What to do if the new thermostat clicks but does not turn on the compressor?
If you hear a characteristic click when you turn the knob, but the compressor is silent, check the voltage at the thermostat input contacts. If there is current, but there is none at the output, the new part may be defective or the temperature range has been incorrectly selected. It is also worth checking the compressor starting relay, which could have burned out during a previous malfunction.
Setup and initial startup of the system
After assembly, the testing stage begins. Plug in the refrigerator and set the temperature regulator to the middle position. Normally, the compressor should start within a few minutes (or immediately if the chamber is warm). If startup occurs, this is a good sign, meaning that the electrical circuit is assembled correctly.
The first hours of operation of the unit require your attention. Listen to how the engine operates: there should be no extraneous knocking or humming that is different from the usual noise. Check the cooling: after 30-40 minutes, the inside of the chamber should become noticeably colder. In this case, a thin crust of ice may begin to form in the freezer.
Do not immediately load the refrigerator with food. Let it run idle for 2-3 hours to reach operating mode and stabilize the temperature background. Only after this can you gradually fill the chambers, making sure that the food does not block the ventilation holes (in No Frost models).
⚠️ Attention: If, after replacing the thermostat, the refrigerator operates in cycles: 1 minute running, 10 minutes standing still, and so on in a circle, this is a sign of incorrect installation of the capillary tube. It does not contact the evaporator properly, and the sensor “thinks” that the cold has already set in.
Common mistakes during self-repair
Independent repair is full of risks, and even experienced craftsmen sometimes make mistakes, not to mention beginners. One of the most common mistakes is neglecting to clean contacts. Oxidized terminals create additional resistance, which leads to heating and eventual melting of the plastic, which can cause a fire.
Another common mistake is incorrect placement of the capillary tube. It cannot be pulled like a string; it must lie freely, but fit tightly to the surface of the evaporator in the fastening area. Excessive tension can lead to a rupture of the tube and leakage of sensitive fluid, after which the thermostat will no longer respond to temperature changes.
- 🔌 Using wires of the wrong size to extend the circuit.
- 🧊 Attempting to replace the thermostat without defrosting the refrigerator (risk of damage to the wiring by ice).
- 🛠️ The use of force when removing plastic panels, leading to breakage of the latches.
It is also worth mentioning the erroneous diagnosis. Sometimes users change the thermostat, although the problem lies in a freon leak. In this case, the new thermostat will work properly, but the refrigerator will not cool, since there is nothing to remove heat to. Therefore, initial diagnosis is critically important.
Questions and answers (FAQ)
Can I use a thermostat from another manufacturer?
Yes, it is possible if the main parameters match: the length of the capillary tube, the temperature range of operation, the overall dimensions and the location of the contacts. However, it is better to look for a complete analogue by catalog number to avoid installation problems.
Why does the refrigerator not turn off after replacing the thermostat?
This may mean that the capillary tube is not immersed deep enough in the cooling zone or is poorly secured to the evaporator. It is also possible that the thermostat is installed with the wrong temperature range (for example, for the freezer instead of the refrigerator).
Is it necessary to defrost the refrigerator before replacing it?
Absolutely yes. Working with electrical wiring and plastic parts inside a wet and icy refrigerator is dangerous and ineffective. Ice can hide the fasteners, and moisture will cause a short circuit when you first turn it on.
How to check the thermostat with a multimeter?
You need to remove the wires from it and ring the contacts. At room temperature, the contacts should be closed (the multimeter beeps). If you put the sensor in the freezer for 10-15 minutes, the circuit should break (the sound will stop). If this does not happen, the part is faulty.