Has the refrigerator stopped humming, or, conversely, makes a loud click, but does not start? In 90% of cases, the culprit of these symptoms is a small but critical element of the electrical circuit - the start-up relay. It is this compact device that is responsible for starting the compressor, which is the “heart” of the entire cooling system.
Understanding this what is the relay used in the refrigeratorallows you not only to diagnose a breakdown, but also often to fix it yourself without calling a technician. This element protects the expensive motor from overloads and ensures its timely switching on and off depending on the temperature in the chambers.
In this article we will analyze in detail the principle of operation of the device, types of relays, their features and diagnostic methods. You will learn how to distinguish a burnt part from other faults and what to look for when purchasing a replacement.
Main function and principle of operation
The main task of the start-up relay is to ensure the start of the compressor engine and its subsequent protection from overheating. Compressors in household appliances are equipped with asynchronous electric motors, which have two windings: working and starting. To start the rotor, a powerful short-term impulse is required, which forms a starting relay.
When the refrigerator is turned on, the current passes through the working winding, creating a magnetic field. At the same time, the starting winding is triggered, creating the phase shift necessary to rotate the rotor. As soon as the engine reaches the required speed, the relay opens the starting winding circuit, and the motor continues to operate only on the working winding. This process takes a split second.
The second important function is protection. Inside the relay housing there is often a built-in thermal protection (bimetallic plate). If the current in the circuit increases to critical values due to a jammed compressor or a power surge, the plate heats up, bends and opens the contacts, completely de-energizing the engine. This prevents the compressor windings from burning out.
⚠️ Attention: If you hear frequent clicks, but the refrigerator does not turn on, immediately unplug it. Operation in the “start-stop” mode can completely destroy the compressor in a matter of minutes.
Thus, the relay performs a dual role: it acts as a starter for the motor and an overload fuse. Without a working relay, the compressor will either not start at all or will overheat, which will lead to expensive repairs.
Types of starting relays
Modern and older models of refrigerators use different types of relays. Understanding their differences is important when selecting spare parts, since they are not always interchangeable. The main division occurs according to the principle of operation.
The most common are induction (starting) relays. They work on the basis of an electromagnet. When current passes through the coil, a magnetic field is created that draws in the core and closes the contacts of the starting winding. As soon as the engine starts and the current drops, the core, under the influence of gravity (or a spring), returns to its original position, opening the circuit. Such devices are often called “tablets” because of their shape.
The second common type is thermal (protective) relays, which are often combined with starting ones in the same housing. They respond to current and temperature. The main element is a bimetallic plate, which deforms when heated. Some models use posistor relays, where the role of a switch is played by a thermistor that changes its resistance when heated.
Is it possible to install a relay from another model?
Yes, it is often possible, but only if the characteristics match. It is important that the following match: the type of compressor (inverter or conventional), voltage, contact location (down or up) and current strength. Universal relays exist, but require correct pinout.
There are also relays for inverter compressors. They are more complex electronic boards that control engine speed. Checking such elements with a multimeter, as is the case with conventional relays, is often impossible - special equipment or replacement with a known-good unit is required.
Signs of malfunction and symptoms of failure
You can determine that the relay has failed by a number of characteristic signs. Users often confuse a relay failure with a malfunction of the compressor or thermostat itself, so it is important to know the exact symptoms.
The most obvious sign is that the refrigerator does not turn on, but it makes a loud click. The engine tries to start, hums for a couple of seconds, then a click is heard (the protection is triggered), and there is silence. After some time, the cycle repeats. This indicates that the trigger mechanism does not work or the contacts are stuck.
Other symptoms include:
- 🔌 Overheating of the case: If the back wall of the refrigerator or the compressor itself becomes hot almost immediately after turning on, the starting winding may not open.
- ❄️ Lack of cold: the compressor works, but does not create enough pressure, since only one winding is working.
- ⚡ Knocking out plugs: a short circuit inside the relay can lead to the operation of circuit breakers in the electrical panel.
- 🔊 Extraordinary noise: rattling or crackling in the compressor area may indicate mechanical destruction of the internal parts of the relay.
If you notice that the refrigerator is running non-stop, this may also be an indirect sign. The relay can “stick” in the closed state, preventing the compressor from going into rest mode, although more often the thermostat is responsible for continuous operation.
Diagnostics: how to check the relay with a multimeter
Before buying a new part, you need to make sure that the old one is faulty. For diagnostics, you will need a multimeter (tester) and a minimum set of tools (screwdriver, pliers). Be sure to disconnect the refrigerator from the power supply before starting any work!
The testing process begins with removing the relay. It is usually mounted on the side of the compressor and covered with a plastic cover. Carefully remove the cover, disconnect the wires and remove the relay itself from the compressor pins. Visually inspect the housing: if there are cracks, traces of burning or melting, replacement is necessary without further checks.
Next, check the continuity of the circuit using a multimeter:
- Turn the multimeter into the continuity or resistance measurement mode.
- Attach the probes to the relay contacts. For the starting relay to be in its normal state, the circuit must be open (infinity resistance).
- Shake the relay next to your ear. If a ringing sound is heard, it means that the internal mechanism is damaged or the contacts are loose - the part is faulty.
- For thermal relays, check the resistance between the input and output. It should be close to zero. If it shows one, the circuit is broken.
☑️ Checklist for checking the relay
It is important to note that checking posistor relays with a multimeter ineffective, since their resistance changes depending on temperature. They are checked by elimination or direct replacement.
Table: Comparison of relay types and their features
For the convenience of systematizing information, we present the main differences in the design and operation of various types of devices. This will help you quickly identify the type of part in your refrigerator.
| Relay type | Principle of operation | Location | Frequent faults |
|---|---|---|---|
| Induction (starting) | Electromagnetic retraction of the core | Contacts down (most often) | Burning of contacts, jamming of the core |
| Thermal (protective) | Deformation of the bimetallic plates | In conjunction with the trigger | Loss of elasticity of the plate, open circuit |
| Posistor | Change in resistance when heated | Any | Destruction of a ceramic element, cracks |
| Electronic (for inverters) | Frequency control via a board | Separate unit or on a compressor | Burnout of electronic components, breakdown of keys |
As can be seen from the table, mechanical relays (induction and thermal) are most susceptible to physical wear of the contacts. Electronic units more often fail due to power surges in the network.
Replacing a relay with your own hands: step-by-step instructions
If diagnostics have confirmed a breakdown, replacing the relay is a procedure accessible even to a novice. The main thing is to follow the sequence of actions and safety precautions. You do not need a soldering iron, since all connections are made through the terminals.
First, purchase an analogue one. You can take an original part by catalog number or a universal relay suitable for the power and type of compressor. Make sure that the location of the contacts on the new relay matches the old one (usually they look down or up).
Replacement algorithm:
- 🔧 Remove the old relay, remembering or photographing the wiring diagram.
- 🧹 Clean the contacts on the compressor from oxides, if they yes.
- 🔌 Place the new relay on the compressor pins until it stops. It should fit tightly.
- 🔗 Connect the wires to the appropriate terminals according to the diagram.
- ✅ Plug in the refrigerator and listen to it start. The motor should work smoothly, without buzzing or clicking.
⚠️ Attention: Do not try to forcefully put on the relay if it does not work. Check the model fit. Loose contact will lead to sparking and fire.
After installation, it is recommended to observe the operation of the refrigerator for 30-60 minutes. The compressor should reach temperature, turn off and turn on again according to the thermostat signal. If the cycle was successful, the repair can be considered complete.
Frequently asked questions and answers (FAQ)
Is it possible repair a burnt-out relay or just replace it?
In most cases, repair is impossible and impractical. The relay housing is often soldered or riveted, and contains complex mechanical or ceramic components inside. Even if you manage to disassemble the device, restoring the factory parameters of the springs or cleaning the contacts with the required accuracy at home is extremely difficult. The cost of a new relay is low, so replacement is the only reasonable solution.
Why does a new relay burn out after a short time?
If replacing the relay did not solve the problem and the new part fails, the reason lies deeper. Most often, this is a malfunction of the compressor itself (turn-to-turn short circuit of the windings), which causes the starting current to increase. The cause may also be improper installation, poor contact in the circuit, or problems with the wiring of the refrigerator. In such cases, diagnostics of the compressor by a specialist is required.
What is the difference between the relays for Atlant, Indesit and Bosch refrigerators?
The difference lies in the design of the housing, the location of the contacts and the current characteristics. For example, relays often have a specific shape and terminal arrangement, different from Italian compressors. Although their operating principle is the same, they may not physically fit in the seat. Always check the markings and appearance. Atlantov relays often have a specific shape and terminal arrangement, different from Italian compressors Indesit. Although their operating principle is the same, they may not physically fit in the seat. Always check the markings and appearance.
Is it dangerous to operate a refrigerator with a faulty relay?
Yes, it is dangerous. In addition to the risk of food spoiling, there is the risk of fire. Sticking contacts or constant attempts to start the compressor lead to strong heating of the wiring and the relay itself. This can cause the plastic elements or wire insulation to catch fire.