A sudden stop of the refrigerator or its inability to maintain the set temperature often becomes an unpleasant surprise that requires immediate intervention. If you notice that the engine hums but does not start, or, conversely, turns on for only a couple of seconds and immediately goes silent, there is a high probability that something has failed. This small but critical component is responsible for starting the compressor engine and protecting its windings from overloads. start-protective relay. This small but critical component is responsible for starting the compressor motor and protecting its windings from overload.
Understanding the principle of operation of this unit will help you not only diagnose the problem, but also, possibly, solve it yourself, avoiding an expensive call to a technician. In this article we will analyze in detail the structure of the mechanism, the symptoms of its breakdown and step-by-step instructions for replacing the part.
The role of the start-up relay in the operation of the compressor
The start-up relay is an electromechanical switch that controls the supply of voltage to the windings of the compressor electric motor. When the refrigerator is turned on, voltage is applied to the starting winding, creating the necessary torque to start the rotor. As soon as the engine reaches the required speed, the relay opens the starting winding circuit, and the motor continues to operate on the main winding.
In parallel with the starting function, the device acts as a thermal fuse. There is bimetallic platelocated inside the case, which reacts to the current strength. If the engine for any reason begins to consume too much energy or overheats, the plate bends and opens the contacts, completely de-energizing the compressor until it cools down.
⚠️ Attention: The internal structure of the relay may vary depending on the model of the refrigerator. There are thermal (induction) and posistronic relays. Replacing one type with another without taking into account the technical characteristics can lead to combustion of the compressor.
Thus, a working relay ensures cyclic operation of the refrigeration unit. If this element stops functioning correctly, the compressor either does not start at all or operates in emergency mode, which inevitably leads to spoilage of food and defrosting of the chamber.
Main signs of a faulty start relay
Diagnostics begins with an analysis of the behavior of the refrigerator. A malfunction rarely occurs suddenly without warning, although it does happen. Most often, the owner notices strange sounds or a change in operating mode.
The most obvious sign is a characteristic click, which is heard approximately 3-5 seconds after an attempt to start the engine, followed by silence. This means that thermal relay triggered and broke the circuit because the engine could not start. If such cycles are repeated regularly, they cannot be ignored.
You should also pay attention to the following symptoms:
- 🔊 The compressor hums, but does not start, emitting a low-frequency hum.
- 🔥 The motor housing or the relay itself gets very hot (becomes hot to the touch).
- 💡 On the back wall of the refrigerator, traces of soot or melted plastic are visible in the relay mounting area.
- 🧊 The temperature in the refrigerator and freezer compartments rises, food begins to deteriorate.
If you observe at least one of these signs, it is necessary to conduct a visual inspection and check of the element. Sometimes the problem lies not in the relay itself, but in starting winding the engine, but diagnostics should begin with the most accessible unit.
Visual diagnostics and preparation for testing
Before picking up a multimeter, you need to remove the suspicious part and inspect it visually. To do this, the refrigerator must be disconnected from the power supply and moved away from the wall, providing access to the rear panel.
Remove the protective cover covering the compressor. The relay is usually placed directly on the motor contact group and secured with clamps or screws. Carefully remove it, having previously photographed the position of the wires, so as not to mix up the contacts during assembly.
During an external inspection, pay attention to:
- 👀 The presence of cracks, chips or melts on the plastic case.
- 👃 The smell of burning or burnt insulation (carefully sniff at the housing holes).
- 🔌 Condition of the contacts: they should be clean, without oxides and carbon deposits.
- 🔩 Integrity of the internal spring (if the design allows you to look inside).
If the relay body is swollen or blackened, further inspection may no longer be possible needed - the part requires replacement. However, even if the device looks intact on the outside, this does not guarantee its serviceability. The internal contacts could simply stick or oxidize.
⚠️ Attention: Before removing the relay, be sure to wait until the compressor has completely cooled down if it has recently been running. Hot metal can cause burns, and sudden cooling of the contacts when removing a hot relay sometimes leads to their deformation.
☑️ Preparation for diagnostics
How to test a relay with a multimeter: step-by-step instructions
For accurate diagnostics, you will need a multimeter switched to resistance measurement mode (Ohm). If you do not have this device, you can purchase it at any electrical goods store or ask your friends.
The verification process depends on the type of relay. Thermal (induction) relays are checked for circuit integrity. PTC posistors (with a ceramic element) require checking the resistance of the posistor. In both cases, it is important to understand which contacts are “ringing.”
Algorithm of actions for checking:
- Shake the relay next to your ear. If a rattling sound is heard, it means that the internal mechanism or contacts are damaged - the part is faulty.
- Identify the contacts. Usually there are three or four. The two main ones are responsible for the passage of current to the compressor.
- Touch the multimeter probes to the contacts. On a working thermal relay, the resistance should be close to zero (the circuit is closed).
- For posistor relays, the resistance of a cold posistor is usually several tens of ohms. If the device shows infinity or zero where it should not be, the relay is faulty.
Separately, it is worth checking the thermal protection. To do this, you need to “ring” the contacts going to the compressor. If the circuit is broken (the multimeter shows one or an infinity sign), it means that the protection has burned out or the contacts have oxidized.
Nuances of checking a posistor
A posistor is a thermistor. When cold it has low resistance. When voltage is applied, it heats up and its resistance increases sharply, opening the starting circuit. It is difficult to check its operation at home, since it requires heating. If visually it is intact and “rings” like a resistor, most likely it is working.
Compatibility table and relay types
When looking for a replacement, it is important to choose an analogue. Relays from different manufacturers may not be physically or electrically compatible. Below is a table to help you navigate the main types of devices.
| Relay type | Principle of operation | Characteristic feature | Examples of brands |
|---|---|---|---|
| Thermal (Induction) | Electromagnetic core | Heavier, metal body, clicks louder | Indesit, Ariston (old models) |
| Posistor | Ceramic thermistor | Lighter, plastic case, quieter | LG, Samsung, Bosch, Beko |
| Combined | Posistor + Thermal protection | Medium weight, complex contact shape | Whirlpool, Electrolux |
| Electronic | Control chip | No moving parts, high accuracy | Modern inverter models |
Please note that conventional relays are not suitable for inverter compressors. In them, the start is controlled by an electronic module, and diagnostics are carried out completely differently. If you have a modern refrigerator with the inscription Inverter, replacing the relay in the classical sense is impossible.
⚠️ Attention: The characteristics of the relay (operation current, voltage) must strictly correspond to the parameters of your compressor. Installing a relay with the wrong current may result in the compressor starting with a delay or burning out from overload.
Replacement process and assembly of the unit
If diagnostics confirm a malfunction, you must purchase a new component. The article number is usually indicated on the body of the old relay. When purchasing, tell the consultant the model of your refrigerator or compressor.
Replacement is carried out in the reverse order. Make sure the new element fits snugly on the motor contacts. A loose fit can cause sparking and heating.
Main installation steps:
- 🛠️ Carefully place the new relay on the compressor contact group until a characteristic click or stop is heard.
- 🔌 Connect the wires to the terminals according to photograph or diagram taken earlier.
- 🔒 Secure the relay body with a metal bracket or screws, if provided by the design.
- 🧹 Replace the compressor protective cover.
After assembly, turn on the refrigerator. The engine should start with a characteristic sound and run smoothly, without humming or periodic clicking. If after 10-15 minutes of operation the compressor does not turn off and the freezer begins to cool, then the repair was successful.
Common mistakes during self-repair
Despite the apparent simplicity of the operation, beginners often make mistakes that can lead to repeated breakdowns or even a fire. One of the most common is ignoring the orientation of the device.
Many relays have a marking UP or an arrow indicating the top position. If you install the part upside down, gravity will not allow the contacts to open or close correctly, which will lead to constant activation of the protection.
It is also dangerous to try to “reanimate” the old relay by stripping the contacts or tapping. Bimetallic plate over time it loses its properties, and such manipulations give only a short-term effect. It is better to immediately install a new part.
Do not forget that a refrigerator is a complex unit. If after replacing the relay the problem does not disappear, the compressor itself may be faulty (turn-to-turn short circuit) or the thermostat. In this case, you cannot do without professional diagnostics.
Is it possible to install a relay from another refrigerator?
Theoretically, it is possible if the electrical characteristics (cut-off current, voltage) and geometric dimensions of the contacts match. However, it is better to look for an original analogue or a universal relay specifically designed for your compressor model. Incorrect selection will lead to unstable operation.
Why does a new relay burn out immediately after installation?
This may indicate problems with the compressor itself. If there is an interturn short circuit in the motor windings, it consumes increased current, which melts the contacts of the new relay. Also, the cause may be a malfunction of the thermostat, due to which the compressor runs non-stop and overheats.
How much does it cost to replace a relay in a service center?
The cost consists of the price of the part itself (usually from 500 to 2000 rubles depending on the model) and the work of the technician. At the service center, the full cost of the service can vary from 2000 to 5000 rubles. Replacing it yourself allows you to save on work.
Is it dangerous to operate a refrigerator with a faulty relay?
Yes, it is dangerous. In addition to food spoilage, there is a risk of the wiring or the compressor itself catching fire due to overheating. In addition, constant attempts to start “shrink” the motor windings, which can lead to an expensive replacement of the entire compressor.