Sudden silence of the refrigerator or, conversely, loud clicks that interrupt the hum of the engine are sure signs that the starting system has failed. Most often, the problem lies in a small but critical detail - start relay. It is this element that is responsible for supplying voltage to the motor windings and its subsequent entry into operating mode. If you notice that the compressor is trying to start, makes a characteristic click and immediately goes silent, most likely this particular part has failed.
Fortunately, replacing the start relay is one of the most accessible procedures in repairing household appliances, which you can do yourself without deep knowledge of electrical engineering. You don’t have to call a technician or take a bulky unit to a service center if you act carefully and follow safety precautions. In this article, we will analyze the structure of the mechanism, methods of accurate diagnosis and a replacement algorithm that will help bring your Indesit, Atlant or LG to life.
Before you begin disassembling, you must completely de-energize the refrigerator. This is a basic safety rule and, if ignored, may result in electric shock. After disconnecting the cord from retail, let the equipment stand for 10–15 minutes so that the capacitors are discharged and the compressor cools down, if it was working before the breakdown.
Design and principle of operation of the starting mechanism
The starting relay is a compact housing, inside which is hidden an electrical circuit that controls engine starting. The main structural elements are an inductor, a movable core and contacts that open or close the circuit. Depending on the model of the refrigerator, the principle of operation may differ: in older models there are often induction relays, and in modern ones there are posistor relays, where the role of the switch is performed by a thermistor.
When you turn on the refrigerator into the network, current passes through the starting winding, creating a magnetic field. Electromagnet retracts the core, closing the contacts and supplying power to the working winding. As soon as the engine reaches the required speed, the current drops, the magnetic field weakens, and the contacts open, returning the motor to normal operation. If this cycle is disrupted, the compressor cannot start or operates with overload.
Modern posistor relays operate on the thermal principle: when current is supplied, the posistor heats up, its resistance increases sharply, and the starting winding circuit is broken. This is a more reliable system, but it is also subject to wear and tear. Understanding exactly what type of device is installed in your unit will help you quickly find the cause of the malfunction.
⚠️ Attention: There may be fragile ceramic elements or springs inside the relay housing. Do not shake the device or try to disassemble it if you plan to reuse it - the seal and calibration will be broken.
Typical symptoms of a relay malfunction
Diagnostics begins long before opening the back panel of the refrigerator. Careful observation of the behavior of equipment allows us to determine with a high degree of probability the nature of the breakdown. If you hear the motor humming for a couple of seconds, then there is a loud click and silence, and after a while the cycle repeats, this is a classic sign of a “failed start.”
Another warning sign is that the compressor is overheating. If you touch the motor body (carefully so as not to get burned) and feel that it is hot, although the refrigerator is not really cold, it means that the starting winding is constantly energized or the motor is operating in blocking mode. Also, a breakdown may be indicated by a burning smell or melted wiring in the connection area.
In some cases, the relay may “stick” in the closed state, which leads to continuous operation of the starting winding. This causes a strong hum and rapid thermal protection, which shuts down the entire unit. In order not to confuse the symptoms with a breakdown of the compressor itself, it is important to carry out a visual inspection and simple measurements.
- 🔊 The compressor makes a loud click and immediately stalls without starting.
- 🔥 The motor housing gets very hot, and the smell of scorched insulation is felt.
- 💡 The light inside the refrigerator is on, but cold is not generated for a long time.
- 📉 There is condensation or ice on the back wall of the chamber, although the thermostat is set to minimum.
Diagnostics: checking the relay with a multimeter
To accurately determine the malfunction, you will need a multimeter - a universal device for measuring electrical parameters. Before starting work, remove the back cover of the refrigerator to gain access to the compressor. Carefully disconnect the wires leading to the relay and remove the plastic housing itself from the contact group.
The initial check is carried out visually. Shake the relay near your ear: if you hear a ringing or knocking sound inside, it means the contacts or core have come off and are dangling loosely. This device definitely requires replacement. Next comes the continuity test using a multimeter in resistance measurement mode.
Connect the multimeter probes to the input and output contacts. In good condition, the resistance should be close to zero (closed circuit) or correspond to the rating specified in the technical documentation. If the device shows one or infinity, it means that something happened open circuit. For posistor relays, it is also important to check the resistance of the posistor itself - it should be in the range of 20–50 Ohms at room temperature.
Nuances of checking a posistor
A posistor is a thermistor that changes its properties when heated. When checking with a multimeter “cold”, it should show a slight resistance. If infinity or zero is immediately visible, the element is faulty. Heating with a hairdryer should lead to a sharp jump in resistance, but at home it is easier to immediately replace the part with a new one, since the service life of old posistors often drops after heating.
Preparation for replacement and selection of spare parts
Replacing the start relay requires not only a serviceable part, but also proper preparation of the workplace. Make sure you have access to the back of the refrigerator from all sides. Prepare in advance flathead and Phillips screwdrivers, pliers and, possibly, electrical tape or heat shrink to insulate the connections.
The most important step is selecting a compatible spare part. Starting relays are not universal: they differ in the type of switching, current strength, number of contacts and method of attachment. There is always a marking on the body of the old relay, for example, PTC 1104 or R600a. You need to look for a replacement strictly according to this code or the model of your refrigerator.
If you cannot find an original spare part, you can use universal analogues, but for this you will have to carefully study the connection diagram. Universal relays often have removable terminals that must be swapped from the old device, maintaining polarity and consistency. An error in the connection can lead to burnout of the compressor windings.
| Relay type | Compatibility | Principle of operation | Visual sign |
|---|---|---|---|
| Induction | Old models (before 2000) | Electromagnetic | Heavy, metal rod inside |
| Posistor (PTC) | Modern refrigerators | Thermal | Lightweight, ceramic disc inside |
| Combined | Specific models | Combined | Larger size, two separate unit |
⚠️ Attention: The technical characteristics of the relay (current strength, refrigerant type) must strictly correspond to the parameters of your compressor. Installing a relay with a lower operating current will lead to its rapid failure.
☑️ Preparation for replacement
Step-by-step instructions for installing a new relay
The replacement process begins with dismantling the old one devices. Carefully disconnect the block with wires from the relay contacts. If the terminals are oxidized or stuck, use pliers, but be careful not to damage the wire insulation. Remove the relay from the contact group of the compressor - usually it is simply put on three pins.
Compare the new and old relay. Make sure the contacts and pin holes on the compressor are aligned. If you are using a universal model, transfer the wires from the old device to the new one, strictly observing the order. For reliability, it is recommended to strip the ends of the wires and crimp them again if they are blackened by heat.
Install the new relay in place, tightly fitting it onto the compressor contacts. Connect the electrical block. Check the secure fit: the device should not dangle. After this, you can conduct a test run. Plug in the refrigerator and listen: the motor should start smoothly, without buzzing or clicking.
If the start-up was successful, let the appliance run for 15-20 minutes without load (without food) to make sure the operation is stable and there is no excessive heating. Only after this can you assemble the back wall and load products.
Common mistakes during self-repair
One of the most common mistakes is ignoring the cause of the breakdown. If the relay burns out, it is often the result of a power surge or problems with the compressor itself. Simply replacing a part may not solve the problem if the network voltage is unstable - the new relay will burn out in a few days or weeks. In such cases, it is recommended to install a stabilizer.
Another error is incorrect orientation of the relay during installation. Many models are sensitive to position in space (arrow “UP” or “DN” on the body). If you install the relay upside down, gravity will not help the contacts open or close at the right time, which will lead to improper operation or combustion.
Also, beginners often forget to check the condition of the thermal fuse, which may be located in the same circuit. If the relay burns out, the fuse could also be damaged. If, after replacing the relay, the refrigerator is silent and does not hum, check the integrity of the entire circuit, including the protective elements.
- ❌ Installing a relay of the wrong power or type.
- ❌ Ignoring the orientation markings (top/bottom) on the case.
- ❌ Poor contact in the terminal box block leading to heating.
- ❌ An attempt to repair the old relay by gluing or stripping the contacts (temporary solution).
Is it possible to repair the old relay rather than changing it?
Theoretically, if the problem is sticking contacts, they can be cleaned, and if winding burnt out - rewind. However, in practice, the service life of the restored relay will be extremely low. Modern relays are inexpensive, and replacing them is a more reliable and safe solution than makeshift repairs.
Why did the new relay burn out after a week?
This indicates an underlying problem. Possible reasons: interturn short circuit in the compressor windings, jamming of the motor piston group, or constant voltage surges in the apartment’s electrical network. In this case, diagnostics of the compressor by a specialist is required.
What is the difference between the relays for R134a and R600a?
Refrigerants require compressors with different characteristics, which means that the starting relays for them have different current characteristics. Relays for R600a (isobutane) are usually designed for lower starting current, since these compressors are more energy efficient. Using the wrong relay will lead to frequent false shutdowns.
How long does it take to replace a relay?
For an experienced technician, the process takes 10–15 minutes. For a beginner who is faced with this task for the first time, including time for diagnostics, removing covers and searching for tools, the repair may take about 40–60 minutes.