The situation when the refrigerator suddenly stops turning off or, conversely, does not want to start after defrosting, often confuses the owner. The first suspect in such cases is thermostat the device responsible for maintaining the specified temperature inside the chambers. Understanding the principle of its operation and the ability to carry out initial diagnostics can save you a significant amount of money on calling a technician or purchasing new equipment.
In this article we will look in detail at how to check the refrigerator thermostat, what tools are required for this and what nuances you should pay special attention to. You will learn to distinguish a sensor failure from a compressor or start relay failure, which is a critical skill for home appliance repair.
The operating principle and design of a temperature sensor
A temperature regulator, or thermostat, is an electromechanical or electronic device that opens and closes an electrical circuit depending on the temperature of the sensing element. In classic mechanical models, inside the case there is bellows tubefilled with freon or other refrigerant. When the temperature changes, the pressure inside the tube changes, affecting the membrane and switching contacts.
Electronic analogs work differently: they use thermistors, the resistance of which changes depending on heating or cooling. The signal is sent to control module, which already makes the decision to start the compressor. Despite the differences in design, they have the same goal - to prevent food from defrosting or, conversely, from deep freezing.
A malfunction of this unit leads to chaotic operation of the refrigeration unit. If the contacts are stuck in the closed position, the compressor will hum non-stop, trying to catch up with non-existent cold. If the circuit is open, the motor simply will not receive a start command, and the chamber will begin to heat up.
⚠️ Attention: Before starting any work on diagnosing the electrical components of the refrigerator, be sure to disconnect the device from the 220V network. Working with live current is deadly.
Understanding what exactly you are testing - a simple “contact” or complex electronics - determines the further repair strategy. Mechanical thermostats, such as TAM 133 or K 59can be tested with a multimeter, while electronic sensors often require checking the resistance in ohms.
External signs of a thermostat malfunction
Before you grab the tools, you should carefully analyze the behavior of your refrigerator. Symptoms may vary, but they always indicate a violation of the temperature cycle. Most often, owners notice that the unit works non-stop, ignoring the set settings.
In other cases, the opposite picture is observed: the refrigerator is silent, it’s warm inside, but the light is on. This may indicate that thermostat it is not sending a signal to start. It is also worth listening to the characteristic clicks - their absence or too frequent repetition may be an indicator of a problem.
- 🔊 The compressor works continuously, without turning off for hours, even if the food inside is clearly frozen.
- 🌡️ The temperature in the main chamber is higher than normal, although the regulator is turned to maximum cold.
- 💡 The light is on, the motor is silent, but after lightly tapping the regulator or turning the knob, a click is heard and it starts.
Sometimes the breakdown is disguised as other defects. For example, if a “coat” of ice has formed in the chamber, but the compressor turns off too early, it is possible that the thermostat capillary tube has lost its seal or has shifted. A visual inspection often helps to identify oxidation of contacts or mechanical damage to the wiring.
Preparation for diagnostics and necessary tools
For a high-quality test, you will need a minimum set of tools, which most home craftsmen will have. The main device will be multimeter (tester), capable of measuring resistance and checking the integrity of the circuit. Without it, diagnostics will be of a mere nature.
Also, do not forget to prepare screwdrivers for removing panels, pliers and, possibly, electrical tape for temporary insulation of wires. It is important to ensure good lighting of the work area, since wires and contacts are often located in hard-to-reach places.
☑️ Preparing to check the thermostat
Before removing the part, it is strongly recommended to take a photo of the wire connection diagram. Insulation colors may vary between models, and it is very easy to confuse them during assembly. Remember or write down which wire goes where so as not to create a short circuit in the future.
Removing the thermostat: step-by-step instructions
The process of removing the thermostat depends on the design of your refrigerator. In most models, such as Atlant or Stinol, the sensor is hidden behind a plastic plug inside the camera or in the lampshade. In some cases, especially in older Biryusa models, it may be located outside, on the back wall.
Carefully remove the temperature control knob by pulling it towards you. Underneath there is usually a mounting screw that needs to be unscrewed. After this, remove the decorative trim. Be careful with the capillary tube - it is a thin copper or aluminum tube that is very easily kinked and damaged.
⚠️ Attention: The capillary tube is filled with gas under pressure. If you bend it or damage it, the thermostat will fail completely, and it can no longer be repaired - only replacement.
Disconnect the wires from the contact group. Modern models use connectors that need to be carefully pulled, while older models use wires that can be pushed onto terminals. Inspect the contacts: if they are blackened or melted, this is a sure sign that thermostat worked with overload or sparked.
Nuances of dismantling in different brands
In Indesit and Ariston refrigerators, the thermostat often is mounted on a special bracket inside the camera. In LG and Samsung models with the No Frost system, the sensor can be combined with the control unit, which complicates diagnostics. Always look for markings on the body of the part before removing.
Methods of checking with a multimeter (testing)
The most reliable way to check the serviceability of a mechanical thermostat is to test the contacts with a tester. To do this, switch the multimeter to resistance measurement mode (Ohm) or continuity mode. First, connect the probes to each other to make sure that the device is working properly - a sound signal should be heard.
At room temperature, the thermostat contacts are usually open (if this is a model for a refrigerator) or closed (for a freezer). However, the exact status depends on the device type. To avoid guessing, use the “cold” method. Place the thermostat sensing tube in the freezer compartment of a regular refrigerator for 10-15 minutes or place it in a container of ice water.
After cooling, check the contacts again. If the device is working properly, when the temperature changes, the resistance should change from “infinity” to zero (or vice versa, depending on the type). If the multimeter shows “1” (open) in both cases, it means that the contacts do not close and the part is faulty.
For electronic thermostats (thermistors), the test is carried out by measuring the resistance at different temperatures. The values must correspond to the resistance table for the specific model. If the resistance does not change or shows a break, temperature sensor requires replacement.
| Contact condition | Multimeter readings | Diagnosis | Action |
|---|---|---|---|
| Closed (during cooling) | 0 - 10 Ohm | Normal | The device is working properly |
| Open (when cooling) | 1 (infinity) | Open circuit | Replacing the thermostat |
| Closed (permanently) | 0 Ohm (always) | Sticking | Replacing the thermostat |
| Floating values | Changing chaotic | Unstable contact | Replacement or cleaning |
Replacement and setting up a new regulator
If the diagnostics show a malfunction, the only option is to buy a new analogue. It is important to choose a thermostat with identical parameters: capillary tube length, temperature range and type of contacts. The marking is usually applied to the body (for example, TAM-133, K-59, RANCO).
Install the new part in the reverse order. Secure the capillary tube in the same place where the old one was, using standard clips. Incorrect position of the tube will lead to incorrect temperature readings and the refrigerator will not work properly.
- ❄️ Make sure that the tube fits tightly to the evaporator for accurate temperature reading.
- 🔌 Check the reliability of the connection of the wires in the terminal block.
- 🔧 After assembly, do not rush to turn on the equipment - let it stand for 2-3 hours to stabilize the refrigerant (if there was a leak in the system).
After the first turn on check the operation of the unit during the day. It should gain temperature and turn off. If the cycle repeats normally, the repair can be considered successful.
⚠️ Attention: The factory settings of the thermostats may differ. If after replacement the refrigerator does not work correctly (does not turn off for too long), adjustment with the screw on the case may be necessary, but it is better to entrust this to a specialist.
Frequently asked questions and answers (FAQ)
Is it possible to temporarily short-circuit the thermostat wires to make the refrigerator work?
Yes, this is possible for diagnostics. If, when you close the wires bypassing the thermostat (directly to the compressor), the refrigerator starts and freezes, then the problem is definitely in the sensor. However, leaving the equipment in this state. it is impossible: it will work without stopping, which will lead to freezing of the evaporator and failure of the compressor.
Why does the new thermostat click, but the compressor does not start?
The click indicates that the contacts are opening and closing, but if the motor is silent, the problem may not be in the thermostat. Check the start relay. compressor, the motor itself or the wiring. It is also possible that the new thermostat is faulty or does not match the specifications.
How to distinguish a thermostat failure from a freon leak?
If the thermostat is faulty, the compressor either works without stopping or does not turn on at all, but the unit itself is cold (if it is turned on directly). but there will be no cold, and the condenser (the grille at the back) will remain cold or warm only partially.
How much does it cost to replace the thermostat?
The cost of the part itself varies from 500 to 2000 rubles, depending on the model of the refrigerator. The work of a replacement specialist usually costs from 1500 rubles. Replacing it yourself allows you to save on the cost. services.
Does the length of the capillary tube affect the operation?
Yes, the length and method of winding the tube affect the response speed of the sensor. If you use a tube much shorter than the standard one, the refrigerator may turn off prematurely, without reaching the desired temperature.