Have you noticed how the refrigerator suddenly becomes silent or, conversely, begins to hum without interruption? Often this is not caused by a compressor breakdown or a freon leak, but by a malfunction of one small but critical control element. Thermostat - this is the component that is responsible for maintaining the temperature balance inside the chambers. Without it, your refrigerator would turn into an uncontrollable freezer or, conversely, into a useless cabinet.
Understanding this how a thermostat worksallows the owner of the equipment not to panic at the first signs of instability, but to correctly diagnose the problem. In this article we will analyze the design of mechanical and electronic sensors, symptoms of their failure and ways to independently check the serviceability of the device.
Many people confuse a thermostat with a thermostat, considering them to be different devices, but in the context of household refrigeration equipment, these are essentially the same functional link. Temperature control occurs precisely due to the opening and closing of contacts inside this node. Let's figure out what exactly happens inside the case and why this process is so important for the safety of products.
The principle of operation and purpose of the thermostat
The main task of the thermostat is to automatically turn the compressor on and off depending on the temperature inside the refrigerator or freezer. It acts as an electrical switch that responds to thermal expansion or contraction of the sensing element. When the temperature reaches the threshold you set (for example, +4°C), the circuit opens and the compressor stops.
Inside the device is capillary tubefilled with gas or liquid (often freon). This element reacts to the slightest changes in thermal conditions. If the chamber gets warmer, the substance in the tube expands, creating pressure on the membrane, which closes the contacts and starts the motor. When cooling, the process proceeds in the reverse order.
⚠️ Attention: In older models of refrigerators, such as Atlant or Stinol, the capillary tube can be quite long and fragile. Any mechanical damage or crease will lead to a complete loss of tightness and failure of the sensor.
Modern models often use electronic temperature sensors, where semiconductor elements work instead of gas and membrane. However, the principle remains the same: receiving a temperature signal and transmitting a command to compressor. The only difference is precision and the absence of moving mechanical parts, which increases the reliability of the system.
Types of thermostats: mechanics versus electronics
In the household appliances market, you can find two main types of temperature control devices. Mechanical thermostats are still widely used in budget and mid-budget models. They are reliable, easy to diagnose and generally cheaper to replace. Their operation completely depends on the physical properties of the gas in the capillary.
- 🔹 Mechanical: they have an adjustment knob, a clicking mechanism, and require physical installation in the evaporator or chamber.
- 🔹 Electronic: they are a board with a thermistor that transmits data to the main refrigerator control controller.
- 🔹 Hybrid: a mechanical handle on the panel, but control is carried out through an electronic board (found in modern LG and Samsung).
Electronic thermal sensors more accurate and allow you to set the temperature in increments of 0.5 degrees. They do not have moving contacts that can burn out, but their diagnostics require a multimeter and knowledge of resistances at different temperatures. The mechanics are often checked by simply “ringing” the contacts or by the exclusion method.
The choice of the type of thermostat depends on the year of manufacture and class of the refrigerator. The model is from the early 2000s, most likely it has a classic mechanics with a bellows tube. In devices with a system No Frost of recent years, electronics integrated into the overall control system are more common.
Main symptoms of a malfunctioning temperature sensor
How to understand what thermostat out of order? Symptoms may vary, but most often it comes down to an incorrect compressor operating cycle. If the refrigerator stops turning off and works around the clock, trying to catch up with the temperature, this is the first alarm signal. In this mode, the motor overheats and food in the refrigerator compartment may freeze.
The opposite situation is that the compressor does not turn on at all, and the chamber becomes warm. This may mean that the contacts inside the thermostat have oxidized and do not close, or the capillary tube has broken. In this case, the refrigerator “thinks” that the temperature is normal and does not start the cooling cycle.
⚠️ Attention: If the refrigerator turns on at 10-15. seconds and immediately turns off, the problem may not be in the thermostat, but in the starting relay or the compressor itself. Do not rush to change the sensor without a comprehensive check.
The third sign is too frequent switching on and off (short cycle). This indicates that differential the temperature is broken, or the sensitive element has lost its seal. ice on the evaporator if the thermostat does not allow the system to enter defrost mode (for models with a drip system).
☑️ Diagnosis of the problem
Where is the thermostat and how to get to it
The location of the thermostat depends on refrigerator designs. In models with one compressor and a drip defrost system, the sensor is usually located inside the refrigeration chamber. Most often, it is built into the lighting lamp or located next to it. The adjustment knob is located outside, and the body and capillary tube are hidden behind a plastic panel.
In two-chamber refrigerators with a system No Frost the mechanical thermostat is often hidden. behind the decorative panel on the ceiling of the refrigerator compartment or in the niche for the lamp. You can get to it by carefully prying up the plastic casing with a screwdriver. It is important not to damage the plastic latches, which become fragile over time.
If you have an electronic refrigerator, the sensor may be located anywhere in the chamber where temperature control is required: in the evaporator, in the air duct, or even in the door. Access to it often requires partial disassembly. internal lining. In freezers, thermostats (especially mechanical ones) are less common, since separate electronic controllers are more often used.
Difficulties of access in different models
In Indesit and Ariston refrigerators, the thermostat is often closed with a plastic cover, which is secured with screws under decorative plugs. In Bosch models, it may be necessary to remove the entire lampshade. lighting. Be prepared for the fact that you will have to unscrew several levels of fasteners.
When dismantling, be sure to unplug the refrigerator! Even if you are only changing the handle, the risk of a short circuit or electric shock when working with internal components cannot be ruled out. This will also protect the electronics from power surges.
Instructions for checking the thermostat. multimeter
For accurate diagnostics, you will need a multimeter. Before starting the test, remove the thermostat and remove the contacts from the wires, having previously photographed the connection diagram. This will help to avoid errors during assembly. Switch the multimeter to the resistance (Ohm) or continuity measurement mode.
Connect the probes to the thermostat contacts. At room temperature, the contacts of a mechanical thermostat (type TAM, K-59, K-57) should be closed, and the device should show zero or emit a sound signal. If there is no resistance (infinity), then the contacts are open. Try immersing the sensitive tube in cold water with ice - the contacts should open.
| Thermostat type | Behavior at room temperature | Behavior in the cold | Diagnosis |
|---|---|---|---|
| Mechanical (normal) | Closed (0 Ohm) | Open (∞) | Good |
| Mechanical (break) | Open (∞) | Open (∞) | Faulty |
| Electronic | Changing | Changes | Need test R |
| Any (short circuit) | Short (0 Ohm) | Short (0 Ohm) | Sticking |
For electronic temperature sensors, testing with a multimeter involves measuring the resistance. The value should change smoothly as the temperature changes. Sudden jumps or breaks indicate a breakdown. Compare the data obtained with the resistance table for a specific refrigerator model.
Replacing the thermostat: step-by-step algorithm
Replacement thermostat is a procedure available to the home handyman, but requires care. The main rule: the new sensor must be a complete analogue of the old one or have compatible parameters (capillary length, temperature range, mounting dimensions). There are practically no universal solutions here.
First, dismantle the old unit by carefully pulling the capillary tube out of the seat. Do not use excessive force to avoid damaging the evaporator. The new sensor is installed in the reverse order. Pay special attention to sealing the hole through which the tube exits into the chamber so that warm air does not get inside.
⚠️ Attention: The ends of the capillary tube of a new thermostat are often sealed or capped to protect against moisture. Do not cut them off ahead of time and do not damage the tube during installation. Gas leakage from the tube makes the thermostat useless.
After installation, assemble the housing, connect the wires according to the diagram made earlier and turn on the refrigerator. During the first few cycles of operation, monitor the behavior of the equipment. You may need additional adjustment a screw on the thermostat body (if there is one) or a knob on the control panel.
Nuances of capillary installation
The tube cannot be bent at an acute angle (bending radius is not less than 30 mm). It also cannot be stretched or compressed. The length of the free part must correspond to the factory one, otherwise the sensor will show the wrong temperature.
Frequently asked questions and answers (FAQ)
Is it possible to temporarily remove the thermostat so that the refrigerator works constantly?
Technically, you can close the contacts directly, but this is strictly not recommended. The compressor will work without stopping, which will lead to its overheating, freezing of food and huge energy consumption. This solution is only for emergency defrosting or compressor testing.
Why does the refrigerator not turn off after replacing the thermostat?
You may have installed a sensor with other temperature parameters (for example, for the freezer instead of the refrigerator). The reason may also be due to incorrect installation of the capillary tube - it should fit tightly to the evaporator. Check the adjusting screw.
How to distinguish a thermostat failure from a freon leak?
When there is a freon leak, the compressor runs constantly, but there is no cold at all, and the condenser (grid at the back) remains cold. If the thermostat breaks down, the compressor is either silent or works, but overcools the chamber, and the condenser will be hot.
How much does it cost to replace a thermostat?
The cost of the mechanical thermostat itself usually varies from 500 to 1500 rubles, depending on the model. Electronic sensors may cost more. The work of the replacement technician is usually assessed separately and depends on the complexity of access to the unit.
Is it necessary to defrost the refrigerator before replacement?
Yes, this is a mandatory requirement for safety and convenience. Working with electrical appliances in damp conditions is dangerous, and ice can damage plastic parts during disassembly. Allow the equipment to completely thaw and dry before starting work.