Sudden stoppage of operation of the refrigerator or The appearance of a loud hum without subsequent starting of the compressor often indicates a failure of the start relay. This small but critical element is responsible for supplying voltage to the motor windings at startup. If the relay is faulty, the compressor either does not start at all, or does so with a characteristic click, after which it goes silent again, which can lead to serious damage to the entire system.
Independent diagnostics of this unit allows you to save significant money on calling a technician, since the verification procedure is quite simple and does not require complex equipment. In most cases, a conventional multimeter and a minimum set of tools are sufficient to determine whether the part needs to be replaced. Start relay is a consumable item, and its failure after several years of operation is considered normal wear and tear.
Before proceeding with disassembly, it is important to make sure that the problem lies precisely in electrical part, and not due to a lack of power in the outlet or a broken cable. If the refrigerator is plugged in, the light inside is on, but the compressor is silent or makes intermittent sounds, the likelihood of a relay malfunction is extremely high. Next, we will look at a step-by-step algorithm of actions for accurate diagnosis.
⚠️ Attention: Before any manipulations with the electrical components of the refrigerator, be sure to disconnect the device from the network! Working under voltage is life-threatening and can lead to electric shock.
Operating principle and types of starting relays
To understand the diagnostic process, you need to know exactly how this unit functions. The starting relay serves as a switch that supplies current to the starting winding of the engine only at the moment of starting, and then turns it off, leaving the working winding. There are two main types of devices used in household appliances: induction (electromagnetic) and positor (thermal).
Induction relays operate due to the magnetic field created by the current in the working winding. When the current reaches a certain value, the core retracts and closes the contacts of the starting winding. After the engine accelerates, the current drops, and the core, under the influence of gravity or a spring, opens the circuit. Such models are sensitive to the position of the housing and are often marked with an "UP" arrow.
Posistor relays, more modern and widespread, use a thermistor element. When voltage is applied, the posistor heats up and sharply increases its resistance, essentially breaking the starting winding circuit. They are less sensitive to vibrations and the position of the refrigerator. Compressors modern brands Indesit, LG i Atlant are most often equipped with posistor models.
What is the difference between relays of different manufacturers?
Structurally, posistor relays may differ in the shape of the housing and the location of the contacts, but their operating principle is identical. Induction relays can be designed for different current strengths, so when replacing, it is important to select an analogue with the same parameters indicated on the housing.
Visual diagnostics and initial inspection
The first stage of testing should always be a thorough visual inspection. Even without the use of measuring instruments, a number of characteristic signs of malfunction can be identified. To do this, you need to remove the back cover of the refrigerator at the bottom, where the compressor is located, and remove the protective casing of the relay itself.
Pay attention to the condition of the plastic housing of the part. If you notice traces of melting, blackening, or smell a persistent burning smell, this is a sure sign that a short circuit or overheating of the contacts has occurred inside. In such cases, further checking with a multimeter is often not required - the part clearly requires replacement.
It is also important to inspect the internal contacts for oxidation. A green or white coating on copper elements indicates poor contact, which could lead to overheating and failure of the unit. If no visual defects are found, we proceed to an instrumental check.
Instrumental test with a multimeter
The most accurate way to determine the serviceability of the relay is to use a multimeter in resistance measurement mode (Ohm). This method allows you to evaluate the condition of the internal contacts and the integrity of the posistor or coil. Before starting measurements, make sure that the part is completely disconnected from the compressor and wires.
For posistor relays, it is necessary to ring the contacts corresponding to the starting winding. In a cold state, the resistance of the posistor should be low (usually several tens of ohms). If the device shows infinity or, conversely, zero, it means the posistor is burnt out or shorted. For induction relays, the integrity of the coil and the mobility of the core are checked.
Checking contacts for breaks is carried out by connecting probes to the input and output terminals. In the initial position (the relay is inverted or, depending on the type), the contacts of the starting winding must be open, and in a certain position (startup simulation) they must be closed. Lack of response or constant resistance indicates sticking or a break.
☑️ Test algorithm with a multimeter
Table of typical faults and symptoms
For quick orientation in the nature of the breakdown, it is convenient to use a summary table. It helps to compare external signs of refrigerator operation with a possible internal relay malfunction. This allows you to weed out other problems, for example, with the compressor itself or the thermostat.
| Symptom | Probable cause in the relay | Multimeter readings | Action |
|---|---|---|---|
| Click, but no start | Sticking contacts or broken posistor | Infinity on the starting contacts | Replacing the relay |
| Humming and overheating | The starting switch does not open winding | Zero Ohm on the contacts in the operating position | Replacing the relay |
| The refrigerator does not turn on | Complete break in the power circuit | No conductivity on any contact | Checking wiring and relays |
| Rare starts with interruptions | Oxidation of contacts | Resistance jumps or is higher than normal | Cleaning or replacement |
It is important to understand that the symptoms may be similar to a malfunction of the compressor itself (turn-to-turn short circuit of the windings). Therefore, if replacing the relay does not help, it is necessary to ring the motor windings. However, statistics show that in most cases with the described symptoms, the starting device is to blame starting device.
Replacement process and features installation
Replacing a refrigerator relay is a procedure that is accessible even to a beginner, if you are careful. After purchasing a compatible part (the marking and connection type must match), you must carefully install it on the three pins of the compressor. It is important not to use excessive force to avoid damaging the motor terminals.
Part orientation is critical, especially for induction models. The case usually has an arrow or the inscription “UP”, which should point straight up. An incorrect position will result in the core not lowering under its own weight, and the starting winding will not turn off, which will cause rapid overheating.
After installation, connect the wires according to the previously taken photo or color marking. Make sure the terminals are tight and not loose. Then reinstall the protective cover and rear panel of the refrigerator. Only after complete assembly can you turn on the device to the network for testing.
Frequent errors during diagnostics and operation
One of the most common mistakes is ignoring the condition of the compressor itself. If a relay burns out, this is often a consequence, not a cause. For example, a difficult engine start due to the exhaustion of the mechanical part creates an increased load on the relay contacts, leading to their burnout. Installing a new relay on a dying compressor will only give a temporary effect.
Also, users often try to clean the contacts of the old relay with sandpaper and it. In modern compact models with plastic cases, this is impossible without destroying the structure. In addition, stripping does not restore the properties of the posistor, which is a disposable element.
Another mistake is using a relay with inappropriate current characteristics. Installing a part designed for less power will lead to its rapid failure. Always check the markings: the numbers after the letters RT (for example, RT-12) or the ampere (A) values must match the original.
⚠️ Attention: Do not try to start the refrigerator bypassing the relay, applying voltage directly to the windings. This is guaranteed to lead to burnout of the compressor starting winding and expensive repairs or replacement of the entire unit.
Questions and answers (FAQ)
Is it possible to check the relay without a multimeter?
Indirectly - yes. If you hear a click when you turn on the refrigerator, the compressor hums for 5-10 seconds and turns off, and the relay housing itself gets very hot or smells like burning, the likelihood of it malfunctioning is 90%. However, to be 100% sure, you need a device.
Why does the relay burn out immediately after replacement?
This indicates that the cause of the breakdown was not in the relay itself, but in the compressor (turn-to-turn short circuit, jamming) or in unstable network voltage. It is also possible that a part with unsuitable current parameters has been selected.
Where can I find the relay markings?
The marking is usually applied to the side or top edge of the plastic case. You need to look for manufacturer designations (for example, Danfoss, Indesit), type (PTC, RKT) and operating current in Amperes.
How much does it cost to replace a relay in the service?
The cost consists of the price of the part itself (it is inexpensive) and the work of the technician. Self-replacement saves up to 70% of the amount that you would have to pay at the service center, since the main part of the price is