When the refrigerator suddenly stops freezing, and from the engine compartment a characteristic click is heard, followed by a buzzing sound and silence, most users panic. When searching for the causes of a malfunction on the forums, you can come across the slang expression “relay burnt out,” which often confuses inexperienced craftsmen. Relay is the popular name for the start-up relay, a small but critical element of the compressor electrical circuit.
It is this component that is responsible for starting the engine and its protection against overloads, so its serviceability directly affects the ability of the unit to maintain low temperatures. Understanding the operating principle of this device will help you carry out initial diagnostics yourself and avoid calling a technician for a simple replacement of a part, the cost of which is usually low.
In this article we will analyze the trigger mechanism in detail, consider the typical symptoms of its failure and provide step-by-step instructions for replacement. You will learn why the compressor may hum but not start, and how to safely check the integrity of the electrical contacts.
What is a relay and why is it needed in a refrigerator
The start-up protection relay, or colloquially “relay,” is an electromechanical device installed directly on the compressor housing. Its main task is to provide a short-term supply of increased current to the starting winding of the engine at the moment of switching on, in order to create the necessary torque for rotating the shaft.
Without this element single-phase asynchronous motor, used in most household refrigerators, would not be able to overcome inertia and start working. After the rotor reaches the required speed, the relay automatically turns off the starting winding, and the engine continues to operate on the main winding.
- 🔌 Provides a starting pulse to the starting winding of the compressor.
- 🛡️ Performs the function of protection against overheating, opening the circuit when the current critically increases.
- ⏱️ Automatically turns off the starting circuit after the motor reaches operating mode.
- 🔊 Extinguishes the electric arc that occurs when the contacts open, extending the service life systems.
In addition to the starting function, the device acts as a thermal fuse. A bimetallic element is often built inside the housing, which opens the contacts if the current in the windings exceeds the permissible limits or if the temperature of the compressor housing becomes too high. This prevents the burning of an expensive engine.
The main types of starting relays and their design
On the household appliances market there are two main types of starting devices, which differ in principle actions and designs. Understanding the differences between them is necessary when selecting spare parts for repair, since they are not always interchangeable without modifying the circuit.
The first type is induction (electromagnetic) relays. They operate using an electromagnetic coil, which, when current is applied, draws in a core that closes the contacts of the starting winding. When the motor accelerates, the current drops, the spring returns the core, and the circuit opens. Such models were often installed in old refrigerators. data-i="67">. These are more modern devices in which the role of a switch is performed by a posistor - a ceramic element that sharply increases its resistance when heated. When voltage is applied, the posistor is cold and passes current; when it heats up, it “cuts off” the starting winding. They are considered more reliable and quieter in operation. Biryusa or Zil.
Second type - posistor (thermal) relays. These are more modern devices in which the role of a switch is performed by a posistor - a ceramic element that sharply increases its resistance when heated. When voltage is applied, the posistor is cold and passes current; when it heats up, it “cuts off” the starting winding. They are considered more reliable and quieter in operation.
| Characteristics | Induction relay | Posistor relay |
|---|---|---|
| Principle actions | Electromagnetic retraction | Thermal expansion (posistor) |
| Audibility of operation | Loud click when starting | Quiet, almost silent |
| Sensitivity to changes | High, contacts may stick | Low, stable operation |
| Typical application | Old Soviet models | Modern refrigerators (LG, Bosch, Samsung) |
It is important to note that posistor relays are often included with a thermal protection relay, forming a single assembly. When diagnosing, it is necessary to check both components, since the failure of one often leads to damage to the second.
Is it possible to install a posistor relay instead of an induction one?
In most cases, yes, but a careful study of the connection diagram is required. PTC relays are often universal and suitable for replacing older models, but the number of contacts and their location must match. Sometimes it is necessary to resolder the wires or use an adapter block.
Typical symptoms of a faulty start relay
You can determine that the problem lies in the “relay” by the characteristic signs that appear in the behavior of the refrigeration unit. Most often, users notice that the refrigerator turned on, the sound of the motor was heard, but after a few seconds there was a click, and there was silence.
If the compressor hums, twitches, but does not start, or starts only after a long period of inactivity (when the posistor has cooled down), this is a sure sign of a malfunction of the starting mechanism. Also, a breakdown is indicated by the lack of cold in the chambers when the light is working and the thermostat is working.
- 🔊 The compressor hums for 5-10 seconds, then a click is heard and the motor stops.
- 🌡️ The refrigerator does not cool, although the indicators are on and the fan (if any) works.
- 🔥 The compressor housing or the relay itself becomes very hot when trying to start.
- 💥 A cracking or sparking sound is heard in the engine compartment area when turned on.
⚠️ Attention: If after clicking the compressor no longer tries to start within 10-15 minutes, this may indicate a trip. thermal protection or complete blocking of the relay mechanism.
Sometimes a relay malfunction causes the compressor to operate continuously without shutting down. This happens if the contacts of the starting winding are “stuck” in the closed position. In this case, the motor operates with overload, which can quickly lead to its turn-to-turn short circuit and costly repairs.
Visual inspection can also give results: a blackened relay body, melted contacts or the presence of carbon deposits on the terminals indicate overheating and disruption of electrical contact inside the device.
Diagnostics: how to check the relay multimeter
Before going to the store for a new part, you need to make sure it is not working. For diagnostics you will need a simple multimeter (tester) and a minimum set of tools. Before starting any work be sure to disconnect the refrigerator from the power supply.
Remove the rear cover of the engine compartment and get to the compressor. The relay is usually mounted on the side of the motor and secured with a bracket or plastic clips. Carefully remove the device, having previously photographed the wiring diagram so as not to confuse them during assembly.
Visually inspect the insides of the relay. If it is an induction model, inside you will see a coil and a movable core with contacts. If posistor - ceramic tablet and contacts. Shake the relay: if you hear the sound of parts coming off inside, the device definitely requires replacement.
Sequence of checking with a multimeter:1. Turn the multimeter into continuity mode (ohmmeter).
2. Attach the probes to the input and output contacts of the relay.
3. In a normal state, the resistance should be close to zero (or show a short circuit).
4. If the device shows “infinity” (open) or high resistance, the relay is faulty.
For posistor relays, it is important to wait for the element to cool completely (about 15-20 minutes after removal), since when it is hot it can show an open circuit, which is its normal operating state. If, after cooling, the continuity shows no contact, the element has burned out.
☑️ Relay diagnostics
Step-by-step instructions for replacing the relay with your own hands
Replacing the start-up relay is one of the most accessible procedures for a home craftsman, which does not require special equipment. The main condition for success is the correct selection of an analogue. The old part number is usually stamped on the housing or indicated on a sticker.
The new relay should match the power of your compressor and the type of refrigerant, although there are universal solutions for most household models. When installing, make sure that the device is correctly oriented: there is often a marking on the case UP or an arrow indicating the top position.
- Unplug the refrigerator from the outlet and provide access to the compressor.
- Remove the old relay by disconnecting the wires and removing the fixing bracket.
- Compare the new and old parts: the number of contacts, their location and shape must match.
- Install the new relay on the compressor terminals, observing the polarity (if indicated) and position.
- Secure the device with the fixing bar and connect the wires as done earlier photo.
- Plug in the refrigerator and listen to it start: the motor should start running smoothly, without buzzing or clicking.
After replacement, it is recommended to monitor the operation of the unit for an hour. The compressor must reach temperature, complete the cycle and turn off. If the cycle repeats normally, and cold appears in the chambers, the repair can be considered successful.
⚠️ Attention: Never install the relay “upside down” or in a position other than the factory one. Violation of the orientation can lead to incorrect operation of the thermal protection or sticking of the contacts.
Frequent questions and possible complications during repairs
Even with successful When replacing a relay, questions or situations may arise when the problem is not solved immediately. Users often wonder: why did the old relay burn out? The reason may be not only natural wear, but also power surges in the network, rare switching on of the refrigerator, or problems with the compressor itself.
If, after replacing the relay, the motor hums but does not start, the compressor itself may have jammed or the motor windings have broken. In this case, simply replacing the relay will not help, and more serious repairs or replacement of the unit will be required. It is also worth checking the capacitor, if it is included in the design of your model.
Sometimes the new relay may click more often than usual. This may be a sign that a device has been selected with inappropriate cutoff current parameters. Using a relay designed for less power will lead to its constant overheating and rapid failure.
Is it possible to repair a burnt-out relay or just replace it?
Theoretically, an induction relay can be disassembled, cleaned of carbon deposits from the contacts and reassembled. However, such a measure is temporary: damaged contact geometry and changed spring properties will lead to repeated failure in the near future. PTC relays cannot be repaired in principle.
How much does a starting relay cost and where can you buy it?
The cost of the part varies from 500 to 2000 rubles, depending on the model and manufacturer. You can buy a relay in spare parts stores for household appliances, at radio markets, or order online using the catalog number. Universal models are cheaper, but require careful installation.
Is it dangerous to operate a refrigerator with a faulty relay?
Operation is strictly not recommended. Constant attempts to start create a huge current load on the compressor windings, which can lead to their burnout. In addition, sticking contacts can cause a fire hazard due to overheating of the wiring.
Regular maintenance, including cleaning the condenser from dust and checking the tightness of the contacts, will help extend the life of both the relay and the entire refrigeration unit. Do not ignore the first signs of unstable operation of the equipment.