If your refrigerator suddenly stops cooling or makes strange noises clicking sounds, the problem often lies in a small but critical component - the start relay. This element is often called the “heart” of the compressor, since it is responsible for starting the engine and protecting the entire system from overloads. Understanding what a refrigerator relay does will help you quickly diagnose a breakdown and avoid costly repairs.
In most cases, owners of household appliances do not even suspect the existence of this part until it fails. Start relay is an electromechanical switch that supplies voltage to the motor windings at the moment of switching on. Without this device, the compressor would simply hum, but would not be able to start, which would ultimately lead to its combustion.
It is important to note that modern refrigerator models, such as LG or Samsung, can use more complex electronic control systems, however classic induction relays are still widespread in technology Atlant, Biryusa and older models Indesit. In this article we will analyze in detail the principle of their operation and signs of malfunction.
Ignoring problems with this unit can lead to failure of the unit itself compressor, the replacement of which is much more expensive. Therefore, if you notice that the unit is operating intermittently, you should immediately pay attention to this component.
Main purpose and principle of operation
The main function of the relay is to provide short-term connection to the starting winding of the compressor motor. At the moment of start, the motor requires significantly more energy than to maintain its operation. It is starting relay that gives this powerful impulse, after which it automatically turns off the starting winding, leaving only the main winding to work.
In addition, the device performs a protective function. There is often a thermal relaylocated inside the case, which opens the circuit when excessive heating or current surges occur. This prevents the insulation from melting and causing the engine to catch fire. The principle of operation is based on the physical expansion of a bimetallic plate or heating of a special tablet, depending on the design.
⚠️ Attention: An attempt to start the compressor directly, bypassing the relay, can lead to instantaneous combustion of the windings or a short circuit in the apartment wiring.
The device operates cyclically: when power is applied, current passes through the coil, creating a magnetic field that draws in the core and closes the contacts of the starting winding. As the motor picks up speed, the current drops, the magnetic field weakens, and the contacts open under the influence of a spring or gravity. This process takes a split second, but it is critically important for the longevity of the entire system.
Types of starting devices
On the household appliances market you can find several types of relays, which differ in design and principle of operation. The choice of a specific type depends on the compressor model and year of manufacture of the refrigerator. Understanding the differences will help when selecting spare parts for repair.
The most common are induction (electromagnetic) relays. In them, the movable core is drawn into the coil when voltage is applied. They are reliable, but sensitive to the position of the refrigerator. There are also posistor (thermal) relays, where the role of a switch is performed by a ceramic element (posistor), which changes its resistance when heated by current.
- 🔌 Induction relays: work by electromagnetic induction, often have a movable core and require strict orientation during installation.
- 🔥 Posistor relays: use the property of ceramics to heat up and lose conductivity, are more compact and less sensitive to vibrations.
- ⚙️ Combined devices: combine a trigger mechanism and thermal protection in one housing, which is typical for many models Whirlpool and Beko.
Electronic relays controlled by a microprocessor are found in inverter refrigerators. They provide smooth starting without sudden current surges, which reduces noise and wear on mechanical parts. However, their diagnosis and replacement require specialized equipment and knowledge.
Symptoms of a relay malfunction
You can determine that a relay has failed by a number of characteristic signs. Most often, owners notice that the compressor tries to start, makes a short beep or click, and then immediately goes silent. After some time, the cycle repeats. This phenomenon is called “cyclic starting.”
Another striking symptom is the constant operation of the compressor without shutting down, which leads to excessive cooling or, conversely, to a lack of cold due to engine blocking. If you hear a loud cracking sound or see sparking in the compressor area, this is a sure sign of damage to the internal contacts.
- 🔊 Frequent clicks: the compressor hums for 2-3 seconds and turns off with a characteristic click.
- 🌡️ Overheating of the case: the back wall of the refrigerator or the compressor itself becomes excessively hot at touch.
- ❄️ Lack of cooling: The light in the chamber is on, but the temperature does not drop, although the motor is running.
Sometimes the relay may “stick” in the on position. In this case, the starting winding remains energized for too long, causing it to overheat and hum. In such cases, it is necessary to immediately de-energize the device.
Why does the relay click?
A click is the sound of contacts opening or closing. If the clicks are frequent, it means that the protection is triggered due to the fact that the engine cannot start. This may be the fault of the relay itself (the contacts are burnt) or a jammed compressor.
Comparison table of relay characteristics
When selecting an analogue for replacement, it is important to take into account not only the appearance, but also the technical parameters. Different compressor models require different amounts of amperage to start. Using an unsuitable relay will either make it impossible to start or burn out the windings.
| Parameter | Induction relay | Posistor relay | Electronic relay |
|---|---|---|---|
| Principle of operation | Electromagnetic | Thermal (resistance change) | Microprocessor control |
| Position sensitivity | High (requires vertical) | Low | Absent |
| Service life | Average (mechanical wear) | High | Very high |
| Replacement cost | Low / Average | Low | High |
The table shows average data. The actual characteristics depend on the manufacturer, for example, relays Danfoss may differ from their Chinese counterparts in terms of switching cycle life. Always check the markings on the body of the old part.
Diagnostics and testing with a multimeter
Before buying a new part, it is worth checking the old one. For this you will need a multimeter. Diagnostics allows you to determine exactly what the problem is: in the relay or in the compressor itself. This will save money and time.
First you need to visually inspect the body. The presence of melting, cracks or a burning smell indicates that the part requires replacement. If everything looks intact, we move on to “dialing” the contacts. Remember that a posistor relay after testing may not work immediately; it needs to cool down (about 5-10 minutes).
☑️ Diagnosing the relay with a multimeter
Checking an induction relay involves shaking it near your ear. If you hear rattling, it means the core is loose or the mechanism is damaged. When checking with a multimeter, the resistance between the main contacts should be close to zero, and between the contacts of the starting winding - also low (if the relay is working properly). Infinite resistance indicates an open circuit.
⚠️ Attention: Before any diagnostics, be sure to disconnect the refrigerator from the power supply! Working with live electricity is life-threatening.
Replacing and installing a new relay
The process of replacing a relay usually does not require complex tools. You will need a screwdriver and possibly pliers. The main thing is to install the new part correctly, observing the orientation (top-bottom) indicated by the arrow on the housing.
First remove the protective cover at the bottom of the compressor. Disconnect the wires and remove the old relay from the compressor rod. Install the new one, pressing it tightly onto the contacts. Make sure that the terminals are tight and not loose.
After installation, turn on the refrigerator. If the compressor starts the first time and runs smoothly, without buzzing or clicking, then the repair was successful. If the problem persists, the compressor or thermostat itself may be faulty.
Frequently asked questions (FAQ)
Is it possible to repair a burnt out relay yourself?
Theoretically, you can try to clean the contacts or replace the coil, but in practice this rarely gives long-term results. Modern relays are non-separable or their repair is not economically feasible. It is cheaper and more reliable to buy a new original or a high-quality analogue.
Why does a new relay burn out quickly?
Frequent combustion of new relays indicates a deeper problem. Most often, this is a malfunction of the compressor itself (turn-to-turn short circuit), problems with wiring, or power surges in the network. Also, the reason may be the incorrect selection of relay power.
How do I know which relay to buy for my refrigerator?
The best way is to look at the markings on the body of the old relay. Look for the model code or technical parameters (current, voltage). You can also search by the model of the refrigerator itself in spare parts catalogs or store consultants.
Does the room temperature affect the operation of the relay?
Yes, at very low temperatures (below +10°C) the oil in the compressor thickens and it is more difficult for it to start. The relay may click while trying to start the engine. In hot weather, on the contrary, thermal protection may work more often. The optimal temperature for operation is from +16 to +32°C.