A situation where the refrigerator stops freezing or, conversely, turns food into ice blocks, often indicates a failure in the temperature control system. The key element of this system is thermostat (thermostat), which is responsible for turning the compressor on and off depending on the specified parameters. If this unit fails, the refrigerator may work continuously or not start at all, which leads to food spoilage and increased energy consumption.
Before calling a technician or buying a new unit, it makes sense to conduct independent diagnostics. Checking the thermostat is a procedure that any DIYer can do with a basic set of tools, and it can eliminate or confirm one of the most common causes of failure. In this article, we will analyze in detail the symptoms of a malfunction, visual inspection methods and an accurate check of electrical contacts using a multimeter.
It is worth noting that in modern electronically controlled models, the function of a mechanical thermostat is performed by a temperature sensor, but the principle of diagnosing the circuit remains similar. However, our main goal is classic mechanical devices installed in most household refrigerators Indesit, Atlant i Beko. Understanding the principle of their operation will help you quickly make a repair decision.
Main signs of a malfunctioning thermostat
The first step in diagnosis is to analyze the behavior of your refrigerator. Mechanical thermostat is a device that opens the electrical circuit when a certain temperature is reached. When it breaks, the contacts can either remain permanently closed or open prematurely. In the first case, the compressor hums non-stop, trying to cool the chamber to an unattainable minimum.
In the second case, the refrigerator is silent, and it gradually becomes warm inside. Sometimes you may notice that the unit turns on, but the operating cycle is too short, not having time to reach the desired temperature. Also, a malfunction may be indicated by sudden freezing of the rear wall or, conversely, a complete absence of frost when the engine is running.
⚠️ Attention: If the compressor runs continuously for more than 12 hours, and the temperature in the chamber does not drop below +5°C, this may indicate not only a breakdown of the thermostat, but also a freon leak or a malfunction of the motor itself.
For a quick initial assessment of the situation, use the survey to determine how typical your situation is for a thermostat failure:
Preparation for diagnostics and safety measures
Any work with electrical appliances requires strict compliance with safety rules. Before you begin disassembling and checking, you must completely turn off the power to the refrigerator. Unplug the power cord from the outlet and provide access to the rear wall of the unit or the internal panel, depending on the model.
You will need a minimum set of tools: flat-head and Phillips screwdrivers for removing the casings, as well as a multimeter (tester) for testing the contacts. If you don't have a multimeter, you can use a simple light bulb with a socket and two wires connected to the mains, but this method is less safe and accurate.
It is important to understand where exactly the thermostat is located. In most single-compartment refrigerators, it is located inside the refrigerator compartment, often hidden behind a plastic panel or combined with the temperature control knob. In two-chamber models, the sensor can be located outside, on the top panel of the case.
Visual inspection and dismantling of the device
Access to the thermostat usually requires removing the protective casing. If the regulator is inside the camera, carefully remove the switch handle and unscrew the mounting screws. Be careful with plastic latches, as the cold makes the plastic brittle and breaks easily.
After removing the device, pay attention to the condition of the capillary tube. This is a thin copper or aluminum tube that transmits temperature from the evaporator to the thermostat sensing element. There should be no dents, creases or signs of corrosion.
Inspect the contacts for traces of carbon deposits or oxidation. If you see black spots or sparking, this is a sure sign that contact group it is burnt out and requires replacement of the entire assembly. Also check the integrity of the insulation of the wires going to the terminals.
| Element | Normal condition | Signs of malfunction |
|---|---|---|
| Capillary tube | Smooth, without deformation | Dents, creases, traces of oil |
| Contact | Clean, without soot | Black plaque, sparking, melting |
| Case | Intact, without cracks | Cracks, traces of overheating |
| Fasting | Tight | Backlash, sensor displacement |
Some thermostat models, for example, from the company TAM or K-59, may have specific fastenings. Make sure you understand the design correctly before making efforts to remove it.
Checking the thermostat with a multimeter (continuity)
The most reliable way to determine serviceability is to check the electrical resistance. Switch the multimeter to resistance (Ohm) or continuity measurement mode. If the thermostat is working properly and is at room temperature, its contacts should be closed.
Connect the multimeter probes to the thermostat contacts. If the device shows zero or a value close to zero, the circuit is intact. If the screen shows one or infinity, the contacts are open. For mechanical thermostats in a warm state, this is normal, but their operation is tested differently.
To check the reaction to cold, place the sensitive part of the thermostat (capillary tube with a can) in the freezer for 15-20 minutes or cover it with ice. After cooling, the contacts should open and the multimeter should show an open circuit. If this does not happen, it means mechanism jammed.
⚠️ Attention: Do not check the resistance by holding the probes with your hands in places of contact with the metal. The resistance of the human body can distort the readings of the device, especially at high measurement limits.
☑️ Checklist for checking with a multimeter
Alternative testing methods without instruments
If you don’t have a multimeter at hand, you can use the exclusion method. This method is less accurate, but often allows you to identify the problem. Disconnect the wires from the thermostat and connect them directly to each other (maintaining insulation!). If, after connecting to the network, the refrigerator started working and began to freeze, it means that the thermostat is faulty.
However, be extremely careful: with this connection, the compressor will work continuously. You will have to manually monitor the temperature in the chamber and turn off the refrigerator so that it does not defrost or freeze everything too much. This method is only suitable for short-term diagnostics.
Another sign is a characteristic click. If the thermostat is working properly, you should hear a clear click when turning the control knob from minimum to maximum and back. The absence of sound may indicate that the internal contacts are stuck or the mechanism is damaged.
Is it possible to temporarily leave the refrigerator without a thermostat?
Technically, it is possible by connecting the wires directly. But then the compressor will work constantly until you unplug the cord from the outlet. This is dangerous due to overheating of the motor and freezing of food. Use this method only for testing and not for permanent use.
Replacing the thermostat and adjusting the temperature
If the diagnostics confirm a malfunction, the thermostat must be replaced. Repairing this unit is usually impractical, since the tightness of the capillary system is broken when opened. Buy a similar model, paying attention to the markings and length of the capillary tube.
When installing a new device, make sure that the sensing element fits snugly against the evaporator or is in the correct position inside the chamber. Incorrect installation will result in incorrect temperature readings even if the device is in working order.
After replacement, adjustment may be required. Rotate the thermostat knob to achieve the desired operating mode. Typically, the optimal position is considered to be one in which the compressor runs for about 10-15 minutes and rests for 20-30 minutes with normal chamber loading.
Frequently asked questions (FAQ)
Is it possible to repair an old thermostat rather than changing it?
At home, repairing a mechanical thermostat is almost impossible and inappropriate. Violation of the tightness of the bellows or changes in the properties of the filler gas require factory equipment. It’s easier and more reliable to buy a new part.
Why does the refrigerator click but does not turn on?
The click can come from the start relay or the thermostat itself. If the clicks are frequent and the engine does not start, the thermostat contacts may be stuck or the compressor start relay may be faulty. Diagnostics of the circuit is required.
How often should you change the thermostat in the refrigerator?
The service life of the thermostat usually coincides with the service life of the refrigerator itself (10-15 years). However, due to voltage fluctuations and natural wear of contacts, it may fail earlier, on average after 5-7 years of active use.
Does defrosting affect the operation of the thermostat?
Regular defrosting prolongs the life of the entire system. If the evaporator is covered with a thick layer of ice, the thermostat may incorrectly read the temperature, since the ice isolates the sensitive element from the air in the chamber.