The situation when the refrigerator stops turning off or, conversely, does not want to start, often puts the owner in trouble dead end In most cases, the culprit of such failures is the thermostat device responsible for maintaining the specified temperature inside the chambers. Understanding the principles of its operation and the ability to carry out initial diagnostics can save a significant amount on calling a technician or avoid damage to food due to sudden defrosting.
Before proceeding with complex manipulations with the multimeter, it is necessary to eliminate the more obvious causes of the malfunction. Users often confuse sensor failure with problems in the defrost system or freon leak. Thermoregulator is a mechanical or electronic switch that closes and opens the compressor power circuit depending on the temperature readings. If this mechanism is “stuck” or loses sensitivity, the cooling cycle is completely disrupted.
In this article we will look in detail at how to check the performance of the thermostat in various ways: from visual inspection to the use of measuring instruments. You will find out what symptoms indicate this particular unit, and receive a step-by-step algorithm of actions for safe diagnosis.
⚠️ Attention: Before starting any work on diagnosing or disassembling the refrigerator, be sure to disconnect the device from the electrical network. Working with live components is deadly.
Main signs of a thermostat malfunction
Diagnostics begins long before you pick up the tools. The behavior of your refrigerator can tell a lot about the condition thermostat. If the unit works non-stop, without turning off for days, this is the first alarm bell. The compressor is trying to increase the temperature, but the sensor does not give a command to stop, since it “does not feel” the cold. As a result, an ice coat may form on the back wall of the chamber, and the food may freeze.
The opposite situation, when the refrigerator is silent and does not turn on, also often indicates a problem with the thermostat contacts. In this case, the circuit simply does not close, and the motor-compressor does not receive power. Sometimes you can hear a characteristic click, but the startup does not occur. This may mean that the sensor mechanism is stuck in the open position. It is also worth paying attention to the temperature in the chamber: if it is noticeably higher than normal, but the compressor does not respond, the problem is most likely in the thermal sensor. A visual inspection can also give clues. If you get to the device itself, pay attention to its body. Cracks, traces of melting or oxidation of contacts indicate that the device has failed. In some models with mechanical control, the regulator knob may dangle or scroll without characteristic clicks, which indicates a breakdown of the internal mechanism. temperature sensor.
Visual inspection can also provide clues. If you get to the device itself, pay attention to its body. Cracks, traces of melting or oxidation of contacts indicate that the device has failed. In some models with mechanical control, the control knob may dangle or scroll without a characteristic click, which indicates a breakdown of the internal mechanism.
- ❄️ The refrigerator operates continuously without turning off, and is very cold.
- 🔇 The unit is completely silent, the compressor does not start, although it is on light bulb.
- 🌡️ The temperature in the chamber does not correspond to the set value on the regulator.
- 🔌 Traces of burning, rust or mechanical damage are visible on the thermostat body.
Where is the thermostat located in different models?
Location thermostat directly depends on the design of the refrigerator and the year of its manufacture. In older models such as Atlant or Biryusa single chamber, the sensor is often located inside the refrigerator compartment. It is easy to recognize by the plastic handle that controls the temperature and the long capillary tube that goes deep into the chamber. To get to the mechanism itself, sometimes it is enough to remove the plastic casing inside the chamber or dismantle the top panel.
In more modern two-chamber refrigerators, for example, Indesit or Stinol, the thermostat is often hidden under the top cover of the housing, above the refrigerator door. To access it, you will need to remove the protective panel, which can be secured with latches or screws. The capillary tube in such models passes through the door seal or the chamber wall, so when dismantling you need to act extremely carefully so as not to damage the thin-walled tube with the refrigerant inside.
In system refrigerators No Frost and models with electronic control, a mechanical thermostat may be absent altogether. Its function is performed by electronic temperature sensors (thermistors), which transmit data to the control module. Checking such elements requires other diagnostic methods, often associated with measuring resistance rather than testing contacts. The location of such sensors varies: they can be mounted in the evaporator, air ducts or the rear wall of the chamber.
⚠️ Attention: The capillary tube of the thermostat is filled with gas or liquid under pressure. It is strictly forbidden to bend it at an acute angle, pierce it or heat it with an open fire, as this will lead to depressurization and failure of the unit.
Features of location in refrigerators of different brands
In Bosch and Siemens refrigerators, the thermostat is often located in a special box behind a decorative trim inside the chamber. In LG and Samsung models with mechanical controls, the sensor may be located in the upper part of the case, which can be accessed after removing the lampshade or top cover. Always check the technical documentation of a specific model, since the layout can change even within the same series.
Testing methods without using a multimeter
If you do not have measuring instruments at hand, you can use traditional diagnostic methods that allow you to determine serviceability with a high degree of probability. thermostat. The simplest way is the elimination method. If the refrigerator does not turn on, try closing the contacts going from the network to the compressor, bypassing the thermostat. To do this, you need to remove the wires from the sensor terminals and connect them together (being careful!). If after this the compressor starts, then the problem is in the thermostat.
Another test option is relevant for a situation where the refrigerator does not turn off. Try removing the thermostat from the chamber (after turning off the refrigerator!) and placing it in a cold environment. For example, you can take the unit out into the cold (in winter) or put it in the freezer, having previously isolated the electrical contacts from moisture. If after 15-20 minutes of being in the cold when connecting to the tester or in the circuit there is no click (contact closure), then the mechanism is not working.
It is also worth paying attention to the length of the capillary tube. If it is too short or, on the contrary, has creases, the sensor will read the wrong temperature. However, this method is more suitable for checking the correct installation after repair. Visually assess the condition of the bellows (corrugated tube): there should be no dents or traces of corrosion that could compromise the tightness of the system.
☑️ Primary diagnostics of the thermostat
Diagnostics of the thermostat multimeter
The most accurate way to check is to use multimeter (tester) in resistance (Ohm) measurement mode or circuit continuity test. This method allows you to objectively assess the condition of contacts and eliminate false conclusions. First you need to dismantle the thermostat and disconnect all the wires from it. Then switch the multimeter to the testing mode and touch the probes to the contacts that come from the power cord and go to the compressor.
At room temperature, the contacts of a mechanical thermostat are usually closed (the device beeps or shows zero). If you turn the knob, at some point there should be a click and the circuit will open (the device will show one or infinity). If there is no click and the resistance does not change regardless of the position of the knob, the thermostat is faulty. For a deeper check, you can cool the sensitive element (capillary tube), for example, by applying a piece of ice to it or using a freezing spray.
The table below shows typical multimeter readings and their interpretation for mechanical thermostats:
| Contact state | Indications multimeter | Regulator action | Verdict |
|---|---|---|---|
| Closed | 0 Ohm (or close to 0) | Knob in the "Max" position | Normal |
| Open | 1 (infinity) | Knob in the "Min" or "0" position | Normal |
| Constantly closed | 0 Ohm | At any position of the knob | Faulty (stuck) |
| Permanently open | 1 |