The situation when the refrigerator stops cooling and the compressor is silent often confuses the owner. The first step is to determine whether this is to blame thermostat or whether the problem lies deeper, in the motor itself or the starting relay. Closing the contacts of the temperature sensor is a classic diagnostic method that allows you to force the engine to start and eliminate a malfunction of the control circuit.
Before taking active steps, it is worth noting that this method is a temporary measure or a testing method. If, after closing the contacts compressor it starts and starts to freeze, it means that the motor itself is working, and the thermostat requires replacement. Ignoring this step can lead to the purchase of unnecessary spare parts when the problem is solved by replacing an inexpensive sensor.
In this article we will analyze in detail the process of searching for contacts, safety precautions and the algorithm of actions. You will learn how to properly prepare the tool, which wires to connect and what absolutely should not be done so as not to permanently damage the equipment. Remember that working with electricity requires care and compliance with all safety precautions.
⚠️ Attention: All work on diagnostics and repair of refrigeration equipment should be carried out only with the power supply completely disconnected from the network. Leaving the device plugged in during disassembly may result in electric shock.
The principle of operation and the role of the thermostat in the system
The thermostat, or thermostat, is a mechanical or electronic device that controls the temperature inside the chambers. Its main task is to open the electrical circuit that supplies voltage to compressorwhen a predetermined low temperature is reached, and close it when heated. Without this element, the refrigerator would operate continuously, which would lead to freezing of food and rapid wear of the motor.
Inside the body of the device there is a sensitive one capillary tubefilled with gas or liquid. When the temperature changes, the volume of the working fluid changes, which leads to mechanical movement of the membrane. This movement opens or closes the contact group. If this mechanism is stuck in the "open" position, the circuit does not close and the motor does not receive a signal to start.
Closing the contacts manually simulates a situation when the chamber has become too warm and urgent cooling is required. This allows voltage to be applied directly to the start relay and the motor. If the system is working, except for the sensor itself, the refrigerator should work at full capacity.
- 🔹 The thermostat is the main “brain” that decides when to turn on the cooling.
- 🔹 The capillary tube reacts to the slightest changes in heat in the evaporator.
- 🔹 Contact group may oxidize or burn over time, losing conductivity.
Required tools and safety measures
To carry out high-quality diagnostics, you will need a minimum set of tools. The main tool will be multimeter (tester), which will allow you not only to close contacts, but also to check the presence of voltage or circuit integrity in the continuity mode. You will also need a screwdriver to remove the panels and insulating tape.
Safety is priority number one. Make sure the floor under your feet is dry and your hands are not wet. If you are using a metal tool to make contacts, hold it only by the insulated handle. Accidentally touching other live circuit components may result in a short circuit or electric shock.
Before starting work, be sure to unplug the power cord from the outlet. Even if you plan to check the operation of the compressor by turning it on, initial access to the contacts and their preparation are carried out only with the device de-energized. This is the golden rule of any repairman.
Searching for contacts and accessing the thermostat
The location of the thermostat depends on the model and year of manufacture of your refrigerator. In most older models, such as Atlant or Biryusa, it is located inside the refrigerator compartment, often hidden by a plastic cover next to the light bulb or temperature controller. In modern systems, access can be through the top of the case or through the rear panel.
After removing the protective cover, you will see the thermostat unit itself with the wires suitable for it. Usually there are two, three or four. To start the compressor, we are interested in precisely those contacts through which the phase goes to the engine. In simple circuits, these are the two main wires that come from the power plug and go to the compressor.
Sometimes the color coding of the wires may not match the standards due to previous repairs or manufacturer characteristics. Therefore, you cannot rely only on the color of the insulation. It is necessary to visually track the path of the wires: one goes from the network (or time relay), the other to the compressor start relay.
| Type of contacts | Wire color (standard) | Function |
|---|---|---|
| Input phase | Brown / Red | Supply voltage from the mains |
| Output to compressor | Black / Green | Transfer current to motor |
| Grounding | Yellow-green | Protection against current breakdown (do not short-circuit!) |
Closing technology for checking the compressor
The closing process itself is extremely simple, but requires care. Once you have identified the two wires (or terminals) you need, they need to be connected to each other. To do this, you can use a piece of insulated wire with stripped ends or a metal jumper. The connection must be tight and reliable.
When the contacts are closed, you can turn on the refrigerator. If the thermostat was faulty and the other components are working properly, you should hear a characteristic click of the starting relay and a starting hum. The compressor will start working continuously, ignoring the temperature in the chamber, since we artificially created the “always on” condition. motor. The compressor will start working continuously, ignoring the temperature in the chamber, since we have artificially created an “always on” condition.
If after closing the contacts there is silence, relay clicks or buzzing without starting, the problem is most likely not in the thermostat. In this case, the diagnosis shifts towards checking the start relay, capacitor or windings of the compressor itself. It is also worth checking the integrity of the wires going from the thermostat to the motor.
- 🔹 Connect the two main wires going to the thermostat, bypassing its contacts.
- 🔹 Plug in the device and listen to the sounds of the engine.
- 🔹 When starting the compressor make sure that it operates smoothly and without vibration.
⚠️ Attention: Do not leave the refrigerator with the thermostat closed unattended for a long time. Since the temperature sensor is now removed from the circuit, the compressor will run continuously. This can lead to deep freezing of food, rupture of the evaporator or overheating of the motor. Use this mode only for short-term diagnostics!
Analysis of results and troubleshooting
If the compressor starts, it means that the power circuit is intact, and the thermostat has really failed. In this case, the only correct solution would be replacement to replace the device with a new one. Repairing the internal mechanical parts of the thermostat at home is impossible and impractical due to loss of tightness and calibration accuracy.
If the motor hums but does not start, or the circuit breaker immediately knocks out, the problem may be a jammed compressor or a faulty start relay. Closing the thermostat helped us understand that voltage was reaching the engine, but there was nothing to start it. Here you will need to replace the start-up protection relay.
Sometimes a situation occurs when, when the contacts are closed, it sparks at the connection point. This indicates poor contact in the circuit or oxidation of the wires. It is necessary to clean the contacts, check the reliability of the connections and only then try again. Oxidation may be the reason that current does not pass even if the thermostat is working.
Replacing the thermostat and final adjustment
After successful diagnosis, it is necessary to install a new thermostat. When purchasing, pay attention to your refrigerator model and length capillary tube. If the tube is too short, it will not reach the desired zone in the evaporator, and the temperature regime will be disrupted. If it is too long, it will have to be carefully laid, avoiding creases.
Installation is carried out in the reverse order of removal. It is important to correctly install the sensitive tube in its original place on the evaporator and secure it with a standard pressure plate. The accuracy of maintaining the temperature in the chamber depends on the quality of the fit of the tube to the surface of the evaporator.
After assembling and connecting the refrigerator to the network, let it work for several hours without loading food. Check if the compressor switches off when the desired temperature is reached. If the on-off cycle is observed, it means that the repair was successful and the system is functioning correctly.
In some cases, it may be necessary to adjust the thermostat rod. There is often a screw on the device body that allows you to adjust the temperature range. However, the factory settings are usually optimal, and you should only interfere with them if you have a special thermometer and an understanding of the processes.
Is it possible to operate a refrigerator with a constantly closed thermostat?
Theoretically, it is possible if you install an external timer or manually turn the device on and off. However, this is extremely inconvenient and dangerous. Without automatic shutdown, the compressor will wear out, and an “ice” will form in the chamber, which will spoil the food and can damage the door seals due to the door being skewed by ice.
Why doesn’t the new thermostat click?
Some modern thermostats are quieter than their old counterparts, and the click may be barely audible. In addition, if the temperature in the chamber has not yet dropped to the shutdown threshold, there will be no click. It is better to check the functionality by cyclically turning the compressor on and off.
What to do if the thermostat wires are reversed?
In most household AC thermostats, polarity does not matter, since the phase wire is broken. However, if the circuit has grounding or specific control circuits (in complex models), reversed wires can lead to a short circuit to the frame. Always check the color marking and diagram of the specific model.