The situation when refrigerator stops cooling, and instead of the usual hum of the compressor you hear only short clicks or a hum that lasts a few seconds, is familiar to many owners of household appliances. Most often, the cause of such a breakdown is the failure of the start-up relay, which is responsible for starting the engine and protecting its windings from overloads. Starting relay - this is a small but critical unit, without which normal operation of the refrigeration unit is impossible.
Diagnostics of this part does not require complex professional equipment, however, it requires basic skills in working with electrical appliances and a multimeter. In this article we will look in detail at how to understand that the problem lies in the relay, how to remove it correctly and measure the resistance in order to accurately determine the need for replacement.
Before proceeding with disassembly, it is important to understand that malfunction can be caused not only by mechanical wear, but also by power surges in the network. If you notice that the engine is trying to start but immediately stalls, or the compressor is getting very hot, do not ignore these signals. A timely check will help to avoid more expensive repairs, such as replacing the compressor itself.
Principle of operation and design of the starting mechanism
The starting protection relay is an electromagnetic switch that supplies voltage to the starting winding of the engine only when it starts. As soon as the compressor rotor reaches the required speed, the current in the circuit drops and the relay opens the contacts, turning off the starting winding. In parallel with this function, the device plays the role of thermal fuse, opening the circuit when the motor overheats.
Inside the body of the part there is a coil, a movable core and contacts, which can be made of various alloys. Modern models often use devices with a posistor - an element whose resistance increases sharply when heated, which leads to a break in the circuit. Understanding this principle helps to understand why, when the relay breaks down, the engine hums but does not start.
⚠️ Attention: There may be refrigerant or oil residues inside the relay if the system is not sealed. Be careful when opening the device case so as not to damage the contacts or get burned from possible sparks when checking under voltage (although we recommend checking only de-energized devices).
The design may vary depending on the manufacturer of the refrigerator. For example, in units Indesit or Ariston one types of relays are often found, while in Atlant or LG there may be completely different modifications. However, the principle of their operation remains similar: to provide a short-term impulse for starting and protect the motor from combustion.
External signs of a relay malfunction
You can determine the breakdown even before disassembling the unit, paying attention to the characteristic symptoms. Refrigerator is a system that signals problems long before a complete stop. If you hear a click, followed by a hum lasting 5-10 seconds, and then another click and silence, this is a classic sign that the starting winding is not receiving an impulse.
Another telltale sign is the compressor housing heating up. If the motor hums but does not start, it begins to consume short circuit current (stall current), which leads to rapid heating. In this case, the thermal relay should operate and turn off the power, but if it is also faulty, the situation becomes emergency.
- 🔊 The compressor makes a loud click, hums for a few seconds and goes silent.
- 🔥 The motor housing gets very hot, although the chamber is warm.
- 💡 The light in the refrigerator is on, but there is no cold at all.
- ⚡ When turned on, the circuit breakers or plugs are knocked out.
Sometimes the cause may not be the relay itself, but an interturn short circuit in the motor windings or jamming of the piston group. However, statistics show that in most cases it is the starting mechanismthat fails first. If after replacing the relay the situation repeats, it means that the problem lies deeper, in the compressor itself.
Preparation for diagnostics: tools and safety
Before checking the start-up relay, it is necessary to ensure safe working conditions. Electric current and household appliances are a dangerous combination, so the first rule is: all work is carried out only on a completely de-energized device. Unplug the power cord from the outlet and make sure that access to the back wall of the refrigerator is free.
To carry out diagnostics, you will need a minimum set of tools. The main device will be a multimeter (tester), which will measure the resistance of the windings and the integrity of the contacts. You will also need screwdrivers to remove the casing and, possibly, pliers to carefully remove the terminals.
☑️ Tools for testing
It is important to inspect the relay mounting location for damage to the insulation or traces of burning. If you see melted plastic or smell burnt wiring, diagnostics may no longer be needed - the part definitely requires replacement. However, to be completely sure and exclude other malfunctions, it is better to take measurements.
Removing the relay from the compressor
The process of removing the part usually does not take much time. On the back wall of the refrigerator, at the bottom, there is a compressor (black tank). A plastic or metal casing is attached to its side or top part, inside of which the desired element is located. Carefully unscrew the mounting screws or press out the housing clamps.
The relay itself is placed directly on the compressor terminals. It is secured by a tight fit and sometimes additional brackets or springs. Before removal, it is strongly recommended to photograph the location of the wires and contacts. This will help you connect the new part correctly or install the old one back if it turns out to be working.
You need to disconnect the wires carefully, holding them by the plastic tips of the terminals, and not by the wires themselves, so as not to break them. If the terminals are oxidized, they can be carefully cleaned, but it is better not to use excessive force to avoid breaking the fragile contacts. After disconnecting all wires, the relay can be removed from the compressor terminals.
⚠️ Attention: Some relay models have a strict installation orientation (top-bottom). Pay attention to the “UP” marking or arrow on the housing before dismantling, so as not to confuse the position during assembly.
Visual inspection and integrity check
After removing the part from the casing, conduct a thorough visual inspection. Shake the relay near your ear: if you hear a rattling sound inside, as if a piece of metal or ceramic has fallen off, then the device is mechanically damaged. This may be the result of a fall or a manufacturing defect.
Inspect the internal contacts. If they are blackened, coated with carbon deposits, or melted, this is an indication that too much current has passed through them or an electric arc has occurred. In such cases, cleaning the contacts usually does not have a long-term effect, and Replacement is the only reasonable solution.
| Symptom | Probable cause | Action |
|---|---|---|
| Scale on the contacts | Sparking during switching | Replacement of the relay |
| Cracks on the body | Mechanical damage | Replacement relay |
| Plastic melting | Overheating due to overload | Checking the compressor and replacing |
| Free movement of internal parts | Destruction of the core | Replacement of the relay |
If there is no external damage, proceed to an instrumental check. For a relay with a posistor, it is important to check its resistance in a cold state. It should be within normal limits (usually several tens of Ohms), and when heated it should go to infinity. It is difficult to check this at home, so they often focus on the resistance of the windings and mechanical integrity.
Is it possible to repair the relay yourself?
Theoretically, you can clean the contacts or replace the posistor, choosing a similar one in resistance. However, in practice, such relays rarely last long after repair. The cost of a new part is low, so the risk of repeated breakdown and defrosting of food is not worth it.
Diagnostics with a multimeter: step-by-step instructions
The most accurate way to determine the condition of a part is to use a multimeter in resistance measurement mode (Ohm). Switch the device to the appropriate range (usually 200 ohms or 2 kohms). First, check the integrity of the inductance coil: attach the probes to the corresponding relay contacts.
If the device shows one (infinity) or zero, then the coil is broken or shorted. In good condition, the resistance should be a certain value, which depends on the model, but usually it is neither zero nor infinity. For thermal relays, it is important to check the bimetallic plate - it should “ring” (show zero) in a cold state.
- 🔌 Connect the probes to the input and output contacts of the coil.
- 📉 Record the resistance readings on the device screen.
- 🔄 Compare the data obtained with the resistance table for your model.
- ⚠️ If there is no resistance or critically low, the relay is faulty.
It is also worth checking the resistance between the contacts that go to the compressor. In normal condition (no voltage applied), the circuit may be open. To check the closure of contacts under load at home, it is safer to use the method of replacing a known-good relay.
Replacement and testing of system functionality
If diagnostics confirm a malfunction, you must purchase a new analogue. The markings are usually applied to the body of the old relay. When purchasing, pay attention not only to the model, but also to the power of the compressor for which it is intended. Installation is carried out in the reverse order of removal.
Place the relay onto the compressor terminals, observing the orientation (arrow up). Connect the wires according to the photograph or diagram you took earlier. Make sure the terminals are tight and not loose. After assembling the casing, you can turn on the refrigerator to the network.
Critical important: listen carefully in the first minutes after switching on operation of the unit. The compressor should start with a characteristic sound, run and shut down when the temperature is reached. If the clicks are repeated, immediately turn off the device from the network - it means that the problem has not been solved or the new element is also defective.Successful start means that starting current was supplied correctly, and the engine entered operating mode. In the future, monitor the temperature of the compressor housing: it should be hot, but not scalding. Regular ventilation of the rear wall of the refrigerator will extend the life of new parts.
How much does a starting relay cost for refrigerator?
The cost of the part varies from 300 to 1500 rubles, depending on the manufacturer and type of relay (posistor or induction). Original spare parts for branded models (LG, Samsung) may cost more than universal analogues.
Is it possible to temporarily start a refrigerator without a relay?
Technically, you can start a three-phase compressor motor without a starting device using a capacitor or a button, but this is extremely dangerous. Without thermal protection, the compressor will burn out in a few minutes or a short circuit will occur. This is strictly not recommended.
Why does a new relay burn out after a short time?
If a new relay fails quickly, the reason is most often in the compressor itself (interturn short circuit, wedge) or in unstable voltage in the network. It is also possible to use relays with unsuitable power parameters.
Where can I find the relay markings?
The marking is applied to the side or top edge of the plastic relay case. It shows the model, voltage, frequency and sometimes the connection diagram. If the inscription is erased, look for the number on the compressor sticker and select a relay from compatibility catalogs.