Sudden silence in the kitchen, interrupted only by the quiet hum of a compressor that never starts, or, conversely, a loud click followed by complete inoperability of the equipment - this is how problems with the starting mechanism often manifest themselves. Start relay is a critical node in the electrical circuit of any refrigeration unit, responsible for starting the compressor engine. Without this small but functionally complex device, correct operation of the refrigerator is impossible, since it is this device that supplies the necessary impulse to the motor windings.
Understanding the operating principle of this component allows you not only to diagnose a breakdown, but also in some cases to fix it yourself, avoiding an expensive call to a technician. In this article, we will analyze in detail the internal structure of various types of relays, consider typical scenarios for their failure and provide a step-by-step algorithm of actions when a malfunction is detected. Accurate diagnostics in the early stages it can save the compressor from overheating and complete failure.
The main task of the element is to briefly connect the starting motor windings when the refrigerator is turned on. As soon as the motor reaches the required speed, the relay should automatically turn off the starting circuit, leaving only the main winding to work. If this process is disrupted, the refrigerator will either not start at all, or will work with constant humming and overheating, which is fraught with serious consequences for the entire cooling system.
Principle of operation and design of the trigger mechanism
The operation of the starting relay is based on the physical properties of electric current and thermal expansion of materials. In the classic induction motor circuit, which is used in most household refrigerators, a phase shift is required to create a rotating magnetic field. This task is performed by starting winding, which is connected only for a split second at the moment of start. The relay acts as an automatic switch that controls this process.
Inside the device body there is a mechanism that responds to current or temperature. The most common thermal relays use a bimetallic strip that bends when heated by current passing through the working winding. This bend mechanically opens the contacts of the starting circuit. Electromagnetic models use a coil that creates a magnetic field sufficient to move the core and open the contacts when the engine reaches a certain speed.
Modern models often combine the functions of starting and thermal protection. Thermal protection relay monitors the temperature of the compressor housing or the current strength. If the motor begins to overheat due to overload or jamming, the protection opens the power circuit, preventing the motor windings from burning out. This two-pronged device is critical for the safe operation of household appliances.
- 🔌 Contact group —provides switching of the electrical circuit of the starting winding.
- 🌡️ Bimetallic plate —a sensitive element that responds to heating or current.
- ⚙️ Spring mechanism - returns the contacts to their original position after cooling.
Technical detail
Inverter refrigerators: In inverter models, the classic There is no start relay. The compressor is started and adjusted by an electronic control unit (inverter), which smoothly changes the frequency of the current. Therefore, searching for a relay in such refrigerators is useless - its function is performed by complex electronics.
Types of starting relays and their features
On the household appliances market there are several main types of starting devices, each of which has its own design features and applications. The most common type is thermal relay, which is often combined with a defense mechanism. It is distinguished by its reliability and relatively low cost, but has an inertia response.
The second popular type is electromagnetic relay. Its operation is based on drawing the core into the coil when a starting current passes. Such devices operate faster and more accurately, but are more sensitive to voltage changes in the network. In powerful industrial or old Soviet refrigerators, just such models were often found.
It is worth mentioning separately positor (solid-state) relays. They use a crystal of semiconductor material (posistor), which, when heated by current, sharply increases its resistance, actually breaking the starting winding circuit. Such devices do not have moving mechanical parts, which makes them silent and durable, but they require time to cool down before the next start.
When selecting a spare part, it is important to pay attention not only to the appearance, but also to the markings. Often compatible brands are indicated on the case, such as Danfoss, Secop or Atlant. A discrepancy between the characteristics can lead to the contacts sticking or, conversely, opening too early, preventing the motor from spinning up.
Typical symptoms of a relay malfunction
Diagnostics of a faulty trigger mechanism usually does not require complex equipment, since the signs of a breakdown appear quite clearly. The most common symptom is a characteristic clicking sound that repeats every few seconds or minutes. The compressor tries to start, a startup sound is heard, but a moment later a shutdown click follows, and the cycle repeats again.
Another alarm signal is the hum of a running engine without switching to operating mode. In this case, the motor shaft does not rotate, although electricity is supplied to the windings. This may indicate that relay contacts they are stuck in a closed state or, conversely, the starting winding does not turn off, causing an overload.
It is also worth paying attention to external signs. If there is a burning smell, smoke or melted plastic in the area of the compressor or the relay itself, this is a direct indication that the device has failed. In such cases, further attempts to turn on the refrigerator are strictly prohibited until the part is replaced.
It is important to distinguish a relay failure from a malfunction of the compressor itself. If after replacing the relay the situation does not change, perhaps the problem lies in the interturn short circuit of the motor windings or mechanical jamming of the piston group. In this case, more serious repairs or replacement of the unit will be required.
Diagnostics and performance testing
Before going to the store for a new part, you need to make sure that the problem lies in the relay. To carry out diagnostics, you will need a multimeter and basic skills in working with electrical appliances. The first step should always be to completely disconnect the refrigerator from the power supply.
After removing the protective casing and dismantling the relay, conduct a visual inspection. Look for signs of soot, melted plastic, or broken housing. If chips or black carbon deposits are visible inside the device, this is a sure sign that contact group it is burnt out. Next comes a test using a tester.
For electromagnetic relays, the test consists of “continuity” of the circuit. In a vertical position (as it stands on the compressor), the circuit between the input and output to the starting winding should ring. If you flip the relay, the circuit should open. PTC devices are characterized by the presence of resistance: in a cold state it amounts to several tens of Ohms, and when heated it tends to infinity.
☑️ Algorithm for checking the relay
⚠️ Attention: When checking with a multimeter, make sure that the device is switched to resistance measurement mode (Ohm). Do not touch the metal probes with your hands during measurements so as not to introduce an error in the readings.
If visual inspection and testing do not reveal obvious defects, but the refrigerator does not work, you can try to gently shake the relay near your ear. If a rattling sound is heard inside, this means that the mechanical parts are damaged or torn off, and the device must be replaced.
Step-by-step instructions for replacing the relay
Replacing the start relay is a procedure that is accessible even to a beginner, if you are careful and consistent. The main rule is safety. Make sure the power cord is unplugged and there is no voltage. Any manipulation of live electrical components is deadly.
Remove the rear metal or cardboard panel of the refrigerator to gain access to the compressor. In most models, the relay is placed directly on the three contacts of the compressor and secured with a metal bracket or plastic latches. Carefully bend the clips and remove the part.
It is important to remember or photograph the position of the wires. In older models, the wires could simply be hanging in the air, and they will need to be connected to the new relay according to the diagram. Newer models often have connectors that simply slide into the mating parts. Install the new device, firmly pushing it onto the contacts until it stops.
| Work stage | Required tools | Key action |
|---|---|---|
| Preparation | Screwdriver, gloves | De-energizing the refrigerator |
| Dismantling | Pliers (optional) | Removing the fixing bracket |
| Installation | No | Putting the new relay on bayonets |
| Fixing | Screwdriver | Fixing the bracket and wires |
| Test | No | Plugging in and listening |
After assembly, do not rush to close the back cover. Turn on the refrigerator and listen. It should start with one click, followed by a steady hum from the compressor. If the clicking cycle repeats, immediately turn off the device - perhaps the wrong relay was selected or the problem is deeper.
Common mistakes during repairs and prevention
One of the most common mistakes is ignoring the cause of failure of the previous relay. If the relay burns out, there is a reason: a power surge, wiring problems, or compressor wear. Simply replacing a part without eliminating the root cause can lead to repeated failure after a short period of time.
An error when selecting analogues is also common. Not all relays are universal. Installing a device with a different type of compressor (for example, installing a posistor instead of an electromagnetic one without changing the circuit) will lead to incorrect operation. Always check the markings and technical specifications.
To extend the life of the relay and compressor, it is recommended to keep the condenser (grid at the back of the refrigerator) clean. Dust leads to overheating of the system, which increases the load on inrush currents and reduces the life of electrical components. Regular cleaning is the best prevention.
⚠️ Attention: Never try to jam the relay contacts in the closed state to “start” the refrigerator. This will lead to the combustion of the compressor starting winding in a matter of seconds, and repairs will become economically unfeasible.
Remember that the life of the starting relay is limited by the number of on-off cycles. Frequent voltage drops in the network cause the relay to operate more often than it should during the cooling cycle, which accelerates its wear. Installing a voltage stabilizer can significantly extend the life of your refrigerator.
Myth about relay repair
There is an opinion that the relay can be disassembled and the contacts can be cleaned with sandpaper. In modern sealed enclosures this is impossible without destruction. Even if you manage to open it, the calibration of the bimetallic plate will be disrupted, and the device will begin to work unpredictably.
Questions and answers (FAQ)
Is it possible to start a refrigerator without a starting relay?
Theoretically, you can start an asynchronous motor by manually applying current to the starting relay winding, but in domestic use this is impossible and extremely dangerous. Without a relay, the motor will not be able to reach operating mode and will burn out due to overheating of the windings. Operating a refrigerator without a working relay is prohibited.
Why does a new relay immediately burn out after installation?
This may indicate a malfunction of the compressor itself (turn-to-turn short circuit), which causes the starting current to exceed permissible limits. Also, the reason may be the incorrect selection of the type of relay or critical voltage drops in the household network.
How to distinguish a thermal relay from an electromagnetic one?
A thermal relay usually has a more complex system of levers and a bimetallic plate, often combined with protection. Electromagnetic is simpler in design, contains a coil and a movable core. Most accurately, the type is indicated in the markings on the case or in the technical documentation for the refrigerator.
How long does a starting relay last on average?
The average service life of a high-quality relay is 5-7 years of active use. However, with frequent power surges or unstable network operation, this period can be reduced to 2-3 years. PTC relays are considered more durable due to the lack of mechanical wear.