A sudden stop of the refrigeration chamber is always stressful, because food supplies are at risk. Often the culprit of a breakdown is a small but critical component - the starting relay, which is responsible for starting the compressor engine. If this element fails, the motor hums, clicks, or shows no signs of life at all, leaving the insides of the unit warm.
Understanding the operating principle of this device will help you independently determine the nature of the malfunction before the technician arrives. In this article we will analyze in detail the structure of the mechanism, the reasons for its failure and testing methods that are available at home.
It is important to note that ignoring the first symptoms of a breakdown can lead to more serious consequences, including burning out the windings of the compressor itself. Therefore, if you notice strange behavior of the equipment, you should not postpone diagnostics.
Functional purpose of the starting relay
The starting relay is an electromechanical switch that supplies voltage to the starting winding of the electric motor only at the moment of its start. As soon as the motor reaches the required speed, the device automatically opens the circuit, turning off the starting winding so that it does not overheat. This process occurs in a fraction of a second and is repeated every time the compressor is turned on.
Modern models of refrigerators, such as Indesit or Atlant, often use posistor relays (PTC), which operate based on changes in resistance when heated. Old models, for example, Soviet Zil or Biryusa, could be equipped with electromagnetic relays with a moving core, the operating principle of which is based on the magnetic field of the coil.
Without a working relay, the compressor cannot go from rest to operating mode. It will try to start, consuming a huge current, but the rotor will not budge. That is why starting relay is considered one of the most vulnerable elements of the electrical circuit of a refrigerator.
⚠️ Attention: An attempt to start a faulty compressor without a relay or with shorted contacts can lead to instant overheating of the windings and expensive repairs motor.
The main symptoms of a relay malfunction
Determine where the problem lies in the starting device, based on a number of characteristic features. Most often, owners notice that the refrigerator has stopped freezing, while the light in the compartment is on. The motor may not respond at all to being connected to the network, or may behave aggressively.
The most common scenario looks like this: the unit turns on, a loud click is heard, the compressor begins to hum, but after a few seconds a second click is heard, and silence ensues. This means that the thermal protection is triggered due to overload because the motor has not started. Sometimes you can hear a characteristic crackling sound, similar to the sound of boiling water, coming from behind.
Visual inspection can also tell a lot about the condition of the part. If you remove the cover from the back of the refrigerator, you will be able to see the device itself. Its body may have traces of burning, melted plastic, or a black coating of soot. In some cases, the relay simply cracks in half.
- 🔊 The compressor hums for 5-10 seconds, then clicks and goes silent.
- 🔥 A burning smell comes from the relay or smoke is visible.
- 🧊 The refrigerator turns on, but the temperature inside is not decreases.
- ⚡ The circuit breaker (traffic jams) in the apartment trips when you try to start.
Types of relays and their design features
For correct diagnosis, you need to understand what type of relay is installed in your unit. In modern household appliances, there are most often two main types of devices, which are fundamentally different in design and testing method.
Electromagnetic relays have a coil and a movable core. When current is applied, the core retracts and closes the contacts of the starting winding. When the current drops (the engine has started), the core falls down under the influence of gravity and opens the circuit. Such devices are position sensitive - they must stand strictly vertically, which is usually indicated by an arrow on the case.
Thermal relays (PTC starters) do not have moving mechanical parts. Inside them there is a ceramic element (posistor), which heats up when current passes and sharply increases its resistance, actually breaking the circuit. After cooling (usually 3-5 minutes) it is ready for use again. These devices are more reliable, but also prone to breakdowns.
| Characteristics | Electromagnetic relay | Thermal relay (PTC) |
|---|---|---|
| Operation principle | Magnetic field coils | Change in resistance when heated |
| Moving parts | Yes (core, contacts) | No |
| Sensitivity to position | High (vertical is needed) | Low (works in any position) |
| Typical service life | Medium (mechanical wear) | High |
Can you change relay types?
Theoretically, if you have adapters and suitable electrical characteristics, this is possible, but in practice it is better to install the original or a complete analogue recommended by the manufacturer to avoid problems with the compatibility of the motor windings.
Detailed instructions for checking with a multimeter
For accurate diagnostics you will need a multimeter. Before starting work, be sure to disconnect the refrigerator from the power supply! Remove the back cover, locate the compressor and carefully remove the start relay. Usually it is fixed with a bracket or simply put on the three pins of the compressor.
First, carry out a visual inspection. Shake the relay near your ear - if something rattles inside, it means the contacts or core have come off, and the device is definitely faulty. Next, proceed to electrical measurements by setting the multimeter to continuity or resistance measurement mode.
For an electromagnetic relay, check the coil resistance. It should be within the normal range (usually tens of ohms). If the device shows infinity (open circuit) or zero (short circuit), the relay needs to be replaced. Also check the contacts: in the initial position they should be open, and when voltage is applied (which is difficult to do at home without a stand), they should close.
Checking the PTC relay is even simpler. Measure the resistance between the contacts. At room temperature it should be small (for example, 20-50 Ohms). If the multimeter shows “1” or infinity, the posistor has burned out. If zero, a short circuit has occurred. In both cases, replacement is required.
☑️ Diagnostic checklist
Step-by-step replacement of the start relay
If the diagnostics confirmed the malfunction, the only solution is replacement. Fortunately, this procedure does not require a complicated tool. You will need a new part with the exact same marking code as the old one.
First remove the old relay. Notice how it was oriented. The housing often has arrows UP or TOPindicating the correct position. Also remember or take a photo of the wiring diagram if there are several of them.
Install the new device on the pins of the compressor. It should fit tightly, without play. If a retaining clip or spring clip is used, be sure to return it to its original position. Securely fasten the wires if you disconnected them.
After installation, close the protective cover and turn on the refrigerator. In the first minutes, listen to the engine. Startup should be smooth, without unnecessary clicks or buzzing. After 15-20 minutes, check whether the evaporator inside the chamber has begun to freeze.
⚠️ Attention: Never try to repair the relay housing with glue or electrical tape. This is a fire hazard and does not restore the electrical properties of the posistor or coil.
Common mistakes when doing self-repair
Home craftsmen often make mistakes that can aggravate the situation. One of the most common is trying to clean the contacts with sandpaper. In modern relays, the contacts are coated with special alloys, and damage to this layer will lead to rapid burnout.
Another mistake is ignoring the condition of the compressor. If the relay burns out, this may be an effect, not a cause. For example, if the compressor is stuck mechanically, it will consume enormous current, which will lead to the burnout of the starting device. Replacing the relay in this case will only give a short-term effect.
Also, you should not leave the refrigerator open for a long time during repairs. If moisture gets on the contacts or inside the compressor compartment, it can cause corrosion and new malfunctions. Work quickly and in dry conditions.
- 🚫 Attempting to solder a cracked relay housing.
- 🚫 Installing the relay upside down (for electromagnetic types).
- 🚫 Ignoring the compressor jam check.
- 🚫 Using a relay with inappropriate power (amperage).
Is it possible to temporarily start a refrigerator without a relay?
Technically, you can start the motor by applying voltage directly to the starting winding, but doing this is strictly not recommended without professional skills. This may lead to a fire or permanent failure of the compressor. This method is only suitable for diagnostics by a technician for a couple of seconds.
Why does a new relay burn out after a week?
Most likely, the problem is not in the relay, but in the compressor itself (turn-to-turn short circuit, wear) or in voltage surges in the network. It is also possible that a relay with unsuitable current characteristics was installed.
How much does it cost to replace a relay in the service?
The cost consists of the price of the part (usually 500-1500 rubles) and the work of the technician. Depending on the region and model of the refrigerator, the total amount can vary from 1,500 to 3,000 rubles.
Where can I find the relay markings?
The marking is applied to the side or top edge of the plastic case. Look for codes like R600, PTC, 123H or manufacturer articles like Danfoss, Indesit, ATN-B130.
Does the temperature in the room affect the operation of the relay?
Yes, especially for thermal relays. In a very cold room (below +10°C), the oil in the compressor thickens, it is harder for the motor to start, and the relay may not cope with the starting current, burning out more often than usual.