Many users are faced with a situation where the refrigerator stops maintaining the set temperature or makes loud clicks when trying to start. At this point, a natural question arises about why there is a relay in the refrigerator and what role it plays in a complex cooling system. Start-protective relay It is one of the key components that ensures safe and efficient operation of the compressor, without which the operation of the entire unit is impossible.
This compact electromechanical device is responsible for engine starting and overload protection, making it a critical element in the electrical circuit. If you hear a characteristic knock or notice that the engine hums but does not start, most likely the problem lies in this unit. Understanding the principle of its operation will help you quickly diagnose a breakdown and make a decision to repair or replace the part.
In this article we will analyze in detail the structure of the mechanism, consider the reasons for its failure and learn how to identify faults without the involvement of expensive specialists. Relay is not just a switch, but a smart protection element that extends the life of your refrigerator by preventing combustion motor windings during voltage surges or jamming of the piston group.
The main purpose of the start-up relay
The main task of this component is to ensure the correct start of the asynchronous compressor motor. When the refrigerator is turned on, the motor rotor is stationary, and to spin it up requires a significant starting current, several times higher than the operating current. It is starting relay that briefly connects the starting winding, creating the necessary torque, and then automatically turns it off when the engine reaches rated speed.
The second, no less important function is protection. If for some reason the engine cannot start or the mechanical part becomes jammed, the current in the circuit increases sharply. In this case, thermal protection, built into the same housing or located nearby, comes into play. It opens the electrical circuit, preventing overheating of the windings and possible fire of the insulation.
Thus, answering the question why there is a relay in the refrigerator, we can say with confidence: this is a guarantor of the safety and stability of the compressor. Without this device, starting the engine would be impossible, and any overload would lead to expensive repairs or a complete replacement of the heart of the refrigeration chamber.
Modern models often use more complex electronic circuits, but the principle remains the same: control of the starting current and protection from emergency situations. Mechanical relay in classic refrigerators it works on the principle of changing the current strength, which makes it a simple but reliable solution for household appliances.
Operation principle and internal structure
To understand exactly how this mechanism works, it is necessary to consider its internal design. A classic relay consists of an inductor, a moving core, contacts and a bimetallic strip. When you turn on the refrigerator, current passes through the coil, creating a magnetic field that draws in the core and closes the contacts of the starting winding.
As soon as the motor rotor begins to rotate and picks up speed, the current in the circuit drops to its normal operating value. The strength of the magnetic field weakens, the core, under the influence of its own weight or spring, falls down, opening the contacts of the starting winding. The engine continues to operate on the main winding. This process takes a fraction of a second and is repeated every time the compressor is turned on.
The protective part of the device is represented by a bimetallic plate that reacts to heat. If the current exceeds permissible limits or the temperature of the compressor housing becomes critical, the plate bends and opens the power circuit. After cooling, it returns to its original position, trying to start the engine again. If the fault is not corrected, the cycle repeats, which we hear as periodic clicks.
⚠️ Attention: Frequent clicking of the relay may indicate a serious problem with the compressor. If, after cooling down and trying to start again, the engine does not start, do not leave the refrigerator plugged in for a long time to avoid permanent failure of the motor.
It is important to note that there are different types of devices, for example, induction and posistor relays. Posistor models, which are often found in modern technology, use a solid-state element that changes its resistance when heated, which eliminates moving parts and increases reliability.
Types of relays: mechanical and posistor
In the household appliances market There are two main types of starting devices, and knowing their differences is important when selecting spare parts. Mechanical relays operating on the electromagnetic principle are classics of the genre. They were installed in Soviet refrigerators and many models of the last century. Their operation is accompanied by a characteristic click, and the service life depends on the quality of the contacts and the condition of the springs.
Posistor (solid-state) relays have no moving parts. Inside them there is a ceramic element - a posistor, which, when voltage is applied, heats up and sharply increases its resistance, actually breaking the starting winding circuit. Such devices are considered more reliable, since there is nothing to wear out mechanically, but they are sensitive to voltage changes in the network.
The choice of relay type depends on the model of your compressor. You cannot simply replace a mechanical relay with a posistor relay without changing the connection diagram, since they have different principles of operation. Below is a table to help compare the main characteristics:
| Characteristics | Mechanical relay | Posistor relay |
|---|---|---|
| Operation principle | Electromagnetic (movement core) | Thermal (change in resistance) |
| Presence of moving parts | Yes (contacts, springs) | No (monolithic block) |
| Sound when operation | Loud click | Quiet or absent |
| Position sensitivity | High (orientation is important) | Low (works in any position) |
| Service life | Limited by contact wear | High (at stable voltage) |
When replacing a part, be sure to pay attention to the markings. Rated current and the type of compressor must match the original. Using an unsuitable relay may result in the engine either not starting or burning out due to untimely disconnection of the starting winding.
⚠️ Attention: Relay specifications may vary between different compressor manufacturers (Danfoss, Atlant, LG). Before purchasing a new part, check the model number on the body of the old relay with the manufacturer's catalog or store consultant.
Typical signs of a relay malfunction
Diagnosing faults in the start-up protection device does not always require sophisticated equipment. Often the symptoms are obvious, and an attentive user can notice them on their own. The first and most common sign is a characteristic sound: the refrigerator hums for a few seconds, then a loud click is heard, and there is silence. After some time, the cycle repeats.
Another alarm signal is the lack of cold when the fan is running (in No Frost systems) or simply warm air in the chambers. The compressor may not turn on at all, or it may turn on for a very short time, after which the protection is triggered. In some cases, a faulty relay can cause sparking inside the housing, which can be noticed if you listen to the operation of the unit in silence.
It is also worth paying attention to the external condition of the part. If during a visual inspection (after removing the casing) you see melted plastic, blackened contacts or smell a burning smell, then the relay has failed. It is strictly prohibited to operate equipment with such a malfunction, as it is a fire hazard.
Sometimes the problem may lie not in the relay itself, but in the motor windings. If the relay is working properly, but the compressor does not start, the starting winding may be broken or the piston may be jammed. In this case, replacing the relay will not help, and more serious repairs or replacement of the compressor will be required.
Is it possible to temporarily remove the relay?
Theoretically, some technicians practice directly starting the compressor without a relay to check its performance. However, it is strictly not recommended to do this at home without special skills. Directly applying voltage to the starting winding without automatic shutdown will lead to its burnout in a matter of seconds. This method is used only for diagnostics in service centers.
How to test a relay with a multimeter
If you decide to carry out diagnostics yourself, you will need a regular digital multimeter. Before starting any work, be sure to disconnect the refrigerator from the power supply! Remove the rear cover at the bottom of the unit to gain access to the compressor. Carefully remove the relay from the compressor contacts, having previously photographed or memorized the connection diagram.
The primary check consists of visual inspection and “shaking”. If something dangles and rattles inside a mechanical relay, it means that the core or contact group has fallen apart - such a device must be replaced. To check the electrical integrity, switch the multimeter to the continuity mode (or resistance measurement).
Here are the main testing steps:
- 🔍 Checking contacts: Terminate the contacts that should be closed in a quiet state. If the device shows infinity (open), then the circuit is broken.
- 🔥 Checking the thermal protection: The resistance of the bimetallic plate should be close to zero. If it shows a break, the protection has burned out.
- ⚡ Checking the coil: Measure the resistance of the inductor. It should be small, but not zero. The absence of resistance indicates a turn short or open circuit.
- 🔄 Orientation: When checking a mechanical relay, it is important to hold it in the correct orientation (upward arrow), since the core works under the influence of gravity.
For posistor relays, the test is simpler: the resistance between the contacts is measured. At room temperature it should be low (tens of ohms). If the resistance is infinitely high or close to zero (short circuit), the part is faulty. After checking, the posistor may remain high resistance for some time until it cools down.
☑️ Diagnostics of the refrigerator relay
Replacing the relay with your own hands: step-by-step instructions
If the diagnostics confirmed a malfunction, the only way out is to replace the part. Fortunately, this process does not require special tools or complex skills, but it does require attention. The main rule is to buy a relay with exactly the same characteristics as the old device. The marking is usually applied to the body.
The replacement process is as follows. First, make sure that the refrigerator is unplugged for at least 15-20 minutes to allow the compressor to cool down. Remove the old relay by disconnecting the wires (if they are at the terminals) or simply pulling it off the compressor contacts. Pay attention to the position of the arrow or inscription UP —the new relay must be installed in exactly the same way.
Install the new part into place, pressing it tightly onto the compressor contacts. If your model has a terminal block, connect the wires according to the photo or diagram you took earlier. Make sure all connections are secure and nothing is loose. Put on the protective cover and secure it.
After assembly, turn on the refrigerator. You should hear the engine start confidently without a prolonged hum. The compressor should operate smoothly, without vibrations or unnecessary sounds. If after a few minutes of operation the relay body does not heat up to a burning state and cold begins to appear in the chambers, then the repair was successful.
⚠️ Attention: If after replacing the relay the refrigerator makes the same sounds (humming and clicking), turn it off immediately. This means that the problem is not in the relay, but in the compressor itself (interturn short circuit, jamming). Further switching on can completely kill the motor.
The influence of network voltage on the operation of the relay
Often users forget that the stability of the relay directly depends on the quality of the power supply in the house. Voltage surges are one of the main reasons for failure of both mechanical, and electronic components of the refrigerator. Low voltage in the network does not allow the relay coil to create a sufficient magnetic field to hold the contacts, which is why they begin to “rattling” or open prematurely.
High voltage, in turn, leads to overheating of the bimetallic thermal protection strip and the coil. This can cause false alarms or, conversely, sticking of contacts, which is deadly for the motor windings. In regions with an unstable power grid, it is recommended to install a voltage stabilizer.
Regular changes in light can significantly shorten the life of the starter protection device. If you notice that the relay changes with alarming regularity (for example, once a year), you should think about checking the wiring in the apartment or installing protective equipment.
Frequently asked questions (FAQ)
Is it possible to start a refrigerator without a relay?
Technically, you can start the engine by applying voltage directly to the starting winding, but doing this manually is extremely dangerous and not suitable for permanent work. Without automatic shutdown of the starting winding, it will burn out in a few seconds. There are special start buttons, but they are a temporary solution and require constant human presence.
Why does the relay click, but the refrigerator does not freeze?
Clicks mean that the relay is trying to start the compressor, but the thermal protection is triggered. There can be three reasons: the relay itself is faulty (the contacts are stuck or the posistor is broken), problems with the compressor (jammed or breakdown of the windings) or critically low voltage in the network.
How to choose an analogue if the original relay cannot be found?
You need to look at the markings. Key parameters: current rating (eg 1/4 HP, 1/5 HP or Amps), refrigerant type (R134a, R600a) and compressor type. You can use universal relay kits that are suitable for a wide range of engines, but it is better to look for an exact analogue in the manufacturer's catalog.
How long does a starting relay last?
The average service life of a high-quality relay is 5-10 years, but it greatly depends on the number of on/off cycles and voltage stability. If there are frequent fluctuations in light or a faulty thermostat (which forces the compressor to work without interruption), the resource can be reduced to 2-3 years.
Is it dangerous to change the relay yourself?
If you follow the safety rules (be sure to unplug it!) and have basic skills in working with tools, replacing the relay is safe. The main thing is not to touch live parts and install the new part correctly. If you are not confident in your abilities, it is better to call a specialist.