Many owners household appliances are faced with a situation where the refrigerator stops cooling, and only a quiet humming sound or a characteristic click is heard from the engine compartment, after which there is silence. At this moment, few people think that the cause of the failure may be a tiny part the size of a matchbox, which is responsible for starting the operation of the entire unit. It is this element, called the starting relay, that is the key link in the engine starting circuit, and without its proper operation, the compressor simply will not be able to gain the necessary speed.
If you notice that your refrigerator hums, but does not start, or the engine tries to turn on and immediately turns off, the problem most likely lies in the starting system. Understanding the operating principle of this unit will help you not only correctly diagnose the fault, but also replace the failed part yourself, avoiding the costly call of a technician. In this article we will analyze in detail the device, functions and methods of checking this important component.
The main function of the starting relay in the refrigerator system
The main task that starting relayis to briefly connect the starting winding of the electric motor compressor. The fact is that single-phase asynchronous motors used in household appliances are not able to independently start rotating the rotor when connected to a standard electrical network. They require an additional impulse created by the phase shift, which is provided precisely by the starting winding.
When the refrigerator is turned on, the relay supplies voltage to the starting winding, creating the necessary torque. Once the motor shaft reaches a certain speed, usually around 75% of rated speed, the relay should automatically turn off the starting winding. If this mechanism does not operate in time, the winding may overheat and burn out, which will lead to expensive repairs of the entire compressor.
There are several types of such devices, but the principle of their operation remains similar: provide a start and immediately exit the circuit. Modern refrigerator models may use electronic control systems, but classic mechanical and thermal relays are still the standard for millions of units of equipment produced over the past decades.
Principle of operation: mechanics and thermal processes
To understand why a part fails, it is necessary to consider its internal structure. Classic relays use the principle of thermal expansion. Inside the case there is a bimetallic plate, which is heated by the current passing through it. When power is applied to the compressor, current passes through the coil or heating element, causing the plate to bend.
This bend mechanically closes the contacts, applying voltage to the starting winding. The engine begins to accelerate, and at the same time the current in the working winding increases. The bimetallic plate continues to heat up, and at a certain moment it sharply opens the contacts, de-energizing the starting circuit. This whole process takes only a few seconds, but it is critical to the life of the motor.
- 🔹 Induction relay: uses a coil that pulls in the core at the starting current, closing the contacts, and when the current drops, the core falls under the influence of gravity.
- 🔹 Thermal relay: relies on heating a bimetallic plate that bends and opens the circuit after the engine warms up.
- 🔹 Posistor relay: a modern version where the role of the switch is played by a thermistor that changes resistance when heated.
It is important to note that which positor (PTC thermistor) is the most reliable solution in modern models, since it has no moving mechanical parts that could jam. However, it also has its own resource of on-off cycles. Understanding the type of your relay will help you choose the right replacement in the event of a breakdown.
Why does the relay click?
The characteristic click when the refrigerator is operating is the sound of the start relay contacts opening. If clicks occur frequently, but the refrigerator does not start, this is a sign that the relay is trying to start the motor, but the protection is triggered due to the impossibility of accelerating the rotor.
Fault symptoms and diagnostic methods
You can determine what starting relay has failed by a number of characteristic signs that appear in the operation of the refrigerator equipment. Most often, users hear repeated clicks at intervals of several seconds or minutes. The motor hums, trying to start, but immediately stalls, after which the thermal protection is activated.
In some cases, the refrigerator may not make any sounds at all if the relay contacts have oxidized so much that the circuit does not close at all. Also, a sign of a malfunction may be a burning smell or a melted plastic casing of the part itself, which indicates overheating due to poor contact or a short circuit inside the windings.
⚠️ Attention: If you smell burning wiring or see sparking in the compressor area, immediately unplug the refrigerator. Operating equipment with a faulty relay can lead to a fire or complete failure of the compressor.
For initial diagnosis, you can use a visual inspection and simple listening. Remove the back cover of the refrigerator and locate the relay on the side fitting of the compressor. Carefully remove it and shake it: if a ringing or knocking sound is heard inside, it means that the internal elements are destroyed. Also check the contacts for the presence of carbon deposits.
Instructions for replacing the start relay with your own hands
Replacing the start relay is one of the few refrigerator repair operations that you can do yourself without special equipment. The main condition is compliance with safety precautions and strict adherence to the sequence of actions. Before starting work, be sure to disconnect the appliance from the power supply.
First you need to gain access to the compressor, which is usually located at the bottom rear of the refrigerator. Remove the protective cardboard or metal cover. You will see a black compressor tank, to which a tube with a plastic box attached to it fits - this is our desired relay.
☑️ Replacing the start relay
Carefully disconnect the wires, having previously remembered or photographed their location. Remove the old relay from the compressor fitting. Install the new part, making sure it fits snugly on the contacts and is oriented correctly (usually the arrow on the body points up). Connect the wires in accordance with the photos taken earlier.
After installation, turn on the refrigerator and listen to the operation of the motor. It should start with a characteristic hum, the relay should click after a few seconds, and the engine will continue to run smoothly. If after 10-15 minutes of operation no problems arise, you can install the protective cover in place.
Table of relay types and their compatibility
When choosing a spare part, it is extremely important to take into account not only the model of the refrigerator, but also the characteristics of the compressor itself. Different manufacturers use different types of starting devices, which are not always interchangeable. Below is a table of the main characteristics for orientation.
| Relay type | Operation principle | Compatibility | Average service life |
|---|---|---|---|
| Thermal (RT) | Bimetallic plate | Old models Atlant, Minsk | 5-7 years |
| Induction | Electromagnetic coil | Soviet refrigerators | 7-10 years |
| Posistor (PTC) | Thermistor | Modern LG, Samsung, Indesit | 10+ years |
| Combined | Heat + Induction | Universal analogs | 5-8 years |
When purchasing a new part, pay attention to the markings. Often the voltage is indicated on the case (for example 220-240V) and the permissible power or current. Using a relay with inappropriate parameters may result in the engine not starting or, conversely, the starting winding not being switched off.
Common mistakes when repairing yourself
Despite the apparent simplicity of the operation, inexperienced craftsmen often make mistakes that can negate all efforts or even harm the equipment. One of the most common mistakes is ignoring the orientation of the relay during installation. Many models only work in a certain position, as they use a gravitational contact return mechanism.
Another mistake is trying to clean the burnt contacts on the old relay and it. This is strictly forbidden. Violation of the geometry of the contacts or a change in the resistance of the material will lead to incorrect operation and re-combustion of the part in the near future. Relay is a consumable item that cannot be repaired.
⚠️ Attention: Never install a relay without making sure that the compressor itself is in good working order. If the motor is jammed or has an interturn short circuit, the new relay will burn out instantly after switching on.
It is also worth mentioning the error with the choice of universal Chinese analogues. Although they are often cheaper than the originals, their plastic quality and bimetal calibration accuracy may be lower. This can lead to the relay turning off too early, preventing the motor from accelerating, or too late, causing overheating.
Is it possible to use a relay from another model?
Theoretically, it is possible if the electrical parameters and mounting dimensions match. However, it is better to look for the original spare part number or a proven analogue recommended by the compressor manufacturer.
Prevention and extension of service life
In order for start relay the entire refrigerator to last longer, it is necessary to ensure proper operating conditions. First of all, this concerns ventilation. The compressor should not overheat, so the distance from the back of the refrigerator to the wall should be at least 10 cm. Dust accumulating on the condenser and around the relay also contributes to overheating.
Regularly, at least once a year, it is recommended to carry out preventive cleaning of the back of the refrigerator from dust and cobwebs. Use a soft brush or vacuum cleaner on low power. Cleanliness in the engine compartment is the key to stable operation of electrical contacts and the absence of parasitic leakage currents.
- 🔹 Ensure stable voltage in the network: voltage surges are detrimental to electronics and relay windings.
- 🔹 Do not turn on the refrigerator immediately after defrosting: let the oil in the compressor drain back into the crankcase (minimum 2-3 hours).
- 🔹 Monitor the level: if the refrigerator is tilted, oil can enter the circulation system, increasing the load on the trigger mechanisms.
Following these simple rules will significantly extend the life of your refrigerator. Remember that the starting relay is the guard of the engine, and its serviceability directly affects the safety of food and your budget.
Is it possible to temporarily start a refrigerator without a relay?
Technically, you can start the engine by applying voltage to the starting winding manually through a button, but doing this in a domestic environment is extremely dangerous and impractical. Without automatic shutdown, the starting winding will burn out in a matter of seconds, which will lead to the need to replace the compressor.
Why does a new relay immediately burn out after installation?
This indicates a more serious problem; most likely, the compressor itself is faulty (jamming, breakdown on the housing) or there are problems with the wiring. Also, the reason may be incorrect selection of the parameters of the new relay (wrong current or type).
How much does it cost to replace the starting relay in the service?
The cost consists of the price of the part (usually from 500 to 2000 rubles, depending on the model) and the cost of the technician’s work. In service centers, the price for work can vary from 1,500 to 3,000 rubles, so replacing it yourself saves a significant amount.
Does the room temperature affect the operation of the relay?
Yes, it does. If the refrigerator is in a very cold room (below +10°C) or, conversely, in a hot room (above +35°C), the thermal mode of operation of the bimetallic plate may be disrupted, which will lead to incorrect response time or startup failure.