Sudden silence of the refrigerator or, conversely, its frantic attempts to turn on and immediately turn off is a sure sign of a malfunction in compressor starting system. In 80% of such cases, the hero of the occasion is the starting relay, which is responsible for supplying voltage to the motor windings. It is this small unit that provides the initial impulse necessary to accelerate the rotor, after which it turns off the starting winding, transferring the work to the main one.
If you notice that your Indesit, Atlant or LG has stopped cooling, and the compressor is humming for only a few seconds, do not rush to call a technician. Self-diagnosis can save a significant amount, since replacing a relay is one of the simplest procedures in repairing household appliances. However, before starting work, it is critically important to de-energize the unit by unplugging the plug from the socket to avoid electric shock.
In this article we will analyze the trigger mechanism in detail, consider the symptoms of its failure and provide a step-by-step test algorithm using a multimeter. You will learn to distinguish a burnt coil from mechanical sticking of contacts and understand when a part really requires replacement, and when the problem lies deeper.
Symptoms of a faulty starting relay
The first bell signaling a problem with starting the engine is a characteristic click, followed by a buzzing sound that ends abruptly silence. The compressor tries to start, but without the participation of a working relay, it cannot overcome the initial resistance and goes into blocking mode. Often this process is accompanied by heating of the motor housing, which indicates an overload of the windings.
In some cases, the refrigerator can operate intermittently, that is, turn on and off chaotically. This occurs when the contacts inside the relay are burnt out but are still able to conduct current, albeit with more resistance. In such a situation, the equipment can work, but consume significantly more electricity, and the temperature in the chambers will fluctuate.
⚠️ Attention: If, after a characteristic click and hum, you smell burnt wiring or see sparking, immediately stop trying to turn it on. Operating a refrigerator with a faulty relay can lead to combustion of the compressor itself, replacing which is not economically feasible.
The main signs of failure also include:
- 🔊 The compressor hums for 5-10 seconds and clicks, then silence.
- 🌡️ The refrigerator body is warm, but the cold does not accumulate.
- ⚡ The automatic switch in the panel is triggered when the refrigerator is turned on.
- 🔥 Strong heating of the back wall in the area of the motor-compressor.
It is important to understand that similar symptoms can be observed when interturn short circuit in the engine itself. Therefore visual inspection and subsequent instrumental diagnostics are mandatory steps to accurately determine the source of the problem.
Design and types of starting relays
Before starting the test, you need to figure out what exactly is inside the plastic case. The starting relay is an electromagnetic switch that automatically switches the circuits of the starting and operating windings of the compressor. Depending on the type of engine and year of manufacture of the refrigerator, the design of the device may differ significantly.
The most common types of devices are posistor and induction. PTC relays, often used in modern models Bosch i Electrolux, do not have moving parts. Their operation is ensured by a thermistor (posistor), which, when heated by current, sharply increases its resistance, breaking the circuit of the starting winding.
Induction (electromagnetic) relays, characteristic of Soviet refrigerators and old models Indesit, operate on the principle of a magnetic field. The current passing through the coil creates a field that draws in the core and opens the contacts. Such devices often have additional thermal protection that turns off the motor if it overheats.
Can you mix relays of different types?
No, it is absolutely forbidden to change a posistor relay to an inductive one and vice versa. They have different operating logic and electrical characteristics. Installing an unsuitable relay will lead to instant failure of either the relay itself or the compressor windings.
The table below shows the main differences between relay types, which will help you quickly identify the part:
|Quiet or no sound|Loud clicking|
| Characteristics | Posistor relay | Induction relay |
|---|---|---|
| Principle of operation | Thermistor heating | Electromagnetic field |
| Moving parts | Absent | Core and contacts |
| Characteristic sound | ||
| Typical brands | LG, Samsung, Beko | Atlant, ZIL, Indesit |
Determining the type of relay is a key point, since the methodology for testing them is somewhat different. PTC resistors often fail due to changes in resistance, and induction ones suffer from mechanical sticking or burning of contacts.
Preparation for diagnostics and dismantling
To carry out high-quality diagnostics, you will need a minimum set of tools: a Phillips screwdriver, pliers and, most importantly, multimeter. Without a tester, it is almost impossible to determine the integrity of internal circuits with high accuracy, since external signs are not always obvious.
The process begins with completely disconnecting the refrigerator from the power supply. It is not enough to simply turn it off with a button or thermostat - you must physically unplug the cord from the outlet. After this, you should move the unit away from the wall, providing access to the rear panel.
Carefully remove the protective cover at the bottom of the rear wall that covers the compressor. Below it you will see a black cylindrical compressor tank, to which a bundle of wires fits. A plastic box is attached directly to the motor terminals - this is the required relay.
☑️ Checklist before starting work
Before removing the part, it is strongly recommended to take a photo of the wire connection diagram. Insulation colors may fade over time and the memory may fail, and incorrectly connecting a new relay will cause it to burn out instantly. Then loosen the clamp or latches securing the casing and remove it.
⚠️ Attention: Do not pull the wires with force. Older refrigerators may have wiring that is dry and brittle. Carefully disconnect the terminals, turning them slightly from side to side.
The removed relay must be carefully inspected. The presence of traces of soot, melted plastic or a characteristic burning smell indicates a breakdown. If the relay body is cracked or has through holes, further checking may be unnecessary - the part definitely requires replacement.
Checking the relay with a multimeter
The most reliable diagnostic method is to use a multimeter in resistance (Ohm) measurement mode. For posistor relays, a normal resistance is considered to be in the range of 20-60 Ohms at room temperature. If the device shows one (infinity) or zero, the posistor is faulty.
An important nuance of checking the posistor: after testing, its resistance may change due to heating by the tester probes. Let the part cool for 15-20 minutes and repeat the measurement. If the readings are radically different from the original ones or do not return to normal, the element requires replacement.
For induction relays the procedure is more complicated. It is necessary to find the contacts going to the starting winding and check them for short circuits. In the normal position (the relay is inverted, as in operation), the contacts should be open. If the multimeter shows a resistance close to zero, it means the contacts are stuck.
Also check the thermal protection relay if it is built into the case. Ring its contacts: when cold they should be closed (resistance close to 0 Ohm). If the tester shows a break, it means that the thermal protection has burned out and requires replacement along with the starting element.
Critical values for diagnostics:
- 📉 A posistor resistance outside the range of 10-100 Ohms is a sign of a malfunction.
- 🔗 A short circuit between the terminals where it should not be is an insulation breakdown.
- 🚫 Lack of conductivity where it should be - an open circuit.
If there is no visual damage, and the tester shows normal values, but the refrigerator does not start, the relay may not hold the load. In such cases, definitive diagnosis is only possible by installing a known-good part.
Typical errors when checking and replacing
One of the most common mistakes is ignoring the condition of the compressor itself. If the motor has a turn-to-turn short, it will draw enormous current, causing the new relay that was just installed to burn out in a few seconds. Therefore, before replacing, it is useful to check the resistance of the windings of the motor itself.
Another mistake is using a relay from a different refrigerator model. Even if they are similar in appearance and fit in the seats, their electrical characteristics (operation current, opening time) may differ. This will either result in the compressor not starting or the starting winding burning out.
⚠️ Attention: Do not attempt to repair the relay by stripping the contacts or gluing the housing. The internal processes of material degradation have already started, and such a “repair” will only lead to a temporary result and the risk of fire.
Often technicians forget to check the capacitor, if it is in the circuit. In some models it is paired with a relay. Bloating of the capacitor housing or loss of capacity can also prevent the engine from starting normally, creating a false impression of a relay failure.
It is also worth mentioning the cleanliness of the contacts. If you nevertheless decide to temporarily revive the induction relay (which is not recommended), make sure that you clean the contacts until they are shiny. Oxides create additional resistance, causing heating and sticking.
FAQ: Frequently Asked Questions
Is it possible to start a refrigerator without a relay?
Technically, you can start the compressor by applying voltage directly to the starting winding, but this is absolutely forbidden to do in a domestic environment. Without a relay, the engine will not turn off the starting winding, which will cause it to burn out after a few seconds. In addition, it is life-threatening.
How much does a starting relay cost and is it difficult to find?
The cost of a relay varies from 300 to 1500 rubles, depending on the brand and type. You can find them in home appliance parts stores. It is important to know the exact model of the refrigerator or the marking of the old relay, since there are practically no universal solutions.
Why does a new relay burn out immediately after installation?
This is a sure sign of a malfunction of the compressor itself (jamming or short-circuiting of the windings) or incorrect selection of the type of relay. Also, the cause may be a power surge in the network if the refrigerator does not have adequate protection.
How can I determine which relay I have?
Carefully inspect the markings on the case. Key words: "PTC" or "POSISTOR" means thermistor relay. If you can hear the ringing of the metal core inside when you shake it, this is an induction relay. You can also find out the type by the catalog number on the Internet.
Regular checks of the condition of the refrigerator and a timely response to changes in its operation allow you to avoid costly repairs. Remember that the start relay is a consumable item, the resource of which is limited by the number of switching cycles, and its replacement is a normal part of equipment maintenance.