Sudden stoppage of the compressor or its hum without starting cooling often indicates a problem in the motor electrical circuit. When the refrigerator stops cooling, and the engine is either silent or makes clicking noises but does not start, the first suspicion falls on the starter protection device. It is this small element that is responsible for supplying the starting pulse and protecting the windings from overheating, being a critically important component of the system.
Self-diagnosis allows you to save time waiting for a technician and understand whether a complex replacement of units is required or it is enough to buy an inexpensive consumable. In this article, we will look at how the relay works, what signs indicate its malfunction, and how to carry out an accurate test using a multimeter to exclude false diagnoses.
Symptoms of a faulty starting relay
You can determine what exactly has failed starting mechanismby the characteristic sounds and behavior of the equipment. Often, users will hear a loud click followed by silence or a low hum that lasts a few seconds until the thermal protection kicks in. This cycle can be repeated every couple of minutes, which is a classic sign that the motor is not receiving the necessary push to start.
In some cases, the compressor tries to start, but a metallic clanging or crackling sound is heard. This may indicate that the contacts inside the device are burnt or stuck, disrupting normal circuit switching. If you notice that the motor housing gets very hot, but cold does not appear in the chambers, this is a sure signal to inspect the electrical part.
It is important to distinguish a relay breakdown from other problems, such as an interturn short circuit in the compressor itself or a freon leak. If the engine hums smoothly and for a long time, but does not start, and a characteristic metallic ringing is heard, the piston group may be jammed. However, if after removing the cover and removing the part you see melted plastic or smell a burning smell, then the diagnosis is obvious.
- 🔊 The compressor makes a loud click and immediately goes silent without starting.
- 🔥 Extreme heating of the engine housing in the absence of cooling.
- 💡 The light inside the refrigerator is on, but the motor does not respond to being turned on.
- 👃 Feeling the smell of naked wiring or melted insulation in the area of the engine compartment.
⚠️ Attention: If after clicking the relay knocks out automatic plugs throughout the apartment, immediately stop trying to turn on the refrigerator. This indicates a serious short circuit in the compressor circuit or wiring, which can result in a fire.
Sometimes the symptoms can be vague, especially in models with inverter systems where the control is electronic. In classic models with asynchronous motors, the symptoms are usually more pronounced. Indesit, Atlant and Stinol often suffer from mechanical wear of the contacts, while in more modern lines, problems may be associated with oxidation of the terminals.
Design and principle of operation of the relay
To ensure high-quality conduction diagnostics, you need to understand how this unit works. The starting protection device is a combination of starting and protective mechanisms combined in one housing. The starting part is responsible for short-term connection of the starting winding of the engine at the moment of start, providing the necessary torque to the rotor.
The protective part, often made in the form of a bimetallic plate, opens the circuit when the permissible current or temperature is exceeded. In electromagnetic models, the contacts close due to the magnetic field created by the current in the winding, and the contacts open when the current drops after the motor spins up. PTC models use a thermistor, which changes its resistance when heated.
Modern refrigerators can be equipped with both electromagnetic and posistor relays. The former have moving contacts and a coil, the latter have no moving parts and work by changing the resistance of the crystal when current passes. Understanding the type of your device will help you choose the right testing method.
What is the difference between a posistor and an electromagnetic relay?
Electromagnetic relays have a moving core and contacts that can burn or stick over time. Posistor (thermoresistive) have no moving parts, they simply increase resistance when heated, turning off the starting winding. PTC resistors are considered more reliable, but are sensitive to voltage surges.
The device body is usually made of heat-resistant plastic and is marked with technical characteristics. It shows the current parameters, the type of compatible compressors and the connection diagram. This data is critically important when selecting a replacement, since installing an unsuitable analogue can lead to burnout of the motor windings.
Preparation for diagnostics and safety measures
Before starting any work with electrical equipment, you must strictly follow safety rules. The first step should always be to completely disconnect the refrigerator from the electrical outlet. It is not enough to simply turn off the button, if there is one - you need to unplug the plug from the socket to ensure that there is no voltage on the contacts.
To carry out diagnostics, you will need a minimum set of tools. The main device will be a multimeter (tester), which allows you to measure resistance and test circuits. You may also need pliers, a screwdriver to remove the protective cover of the engine compartment, and possibly a needle file to clean out the contacts if you plan to restore the old part.
☑️ Preparing to check the relay
Provide a comfortable workplace, since access to the compressor is often limited. If the refrigerator is built-in, it may have to be removed from the niche. Remember that the compressor may be hot if it has just been running, so allow the equipment to cool for 15-20 minutes before disassembling.
⚠️ Warning: Insects or rodents may live in the engine compartment, especially if the equipment has been sitting in a garage or country house for a long time. Be careful when accessing the bottom of the refrigerator to avoid stings or contact with allergens.
Visually inspect the wires leading to the compressor. If the insulation is melted or there is evidence of rodents, restoration may not be safe. In such cases, it is better to replace the damaged sections of the wiring before installing a new relay.
Removing the starter protection device
The process of removing the relay is quite simple, but requires care. On most refrigerator models, such as Bosch, Liebherr or Biryusa, the relay is placed directly on the compressor contact rod and secured with a metal bracket or plastic latches. First you need to remove the protective casing, which is usually held on with screws or simply snapped on.
After removing the casing, you will see a box attached to the side of the compressor. Carefully disconnect the wires, first photographing their location or sketching the diagram. This will help to avoid errors during assembly, since reversed polarity or connection to the wrong terminals can damage the device instantly.
If the relay is held on a bracket, it must be bent or removed. In some designs, for example, in older models ZIL or MHM, the relay can be mounted on a separate strip next to the compressor. Remove the part smoothly, without jerking, so as not to damage the fragile ceramic internal elements or compressor leads.
| Refrigerator model | Relay mounting type | Location | Features removal |
|---|---|---|---|
| Atlant MXM | Attachment to the rod | On the side of the compressor | Requires removal of the metal bracket |
| Indesit C138 | Attachment to the rod | Side/bottom | Fixation with plastic latches |
| Stinol 103 | Attachment to the rod | Side of the compressor | Two screws securing the housing |
| Biryusa 6 | Separate (rarity) | Next to the motor | Fixing with screws to the frame |
After removing the device, inspect it externally. The presence of cracks, melting, soot or a characteristic burning smell indicates the need for replacement. If there are no visual defects, we proceed to an instrumental check.
Checking the relay with a multimeter
The most accurate diagnostic method is checking the resistance using a tester. For electromagnetic relays, it is necessary to ring the winding. Switch the multimeter to resistance measurement mode (Ohms) and connect the probes to the appropriate contacts. The resistance of a working coil is usually several tens of ohms, the exact value depends on the model.
If the device shows one or infinity, it means there is a break in the winding, and the relay must be replaced. If the resistance is close to zero, a short circuit of the turns has occurred. It is also important to check the contacts: in the initial position they can be open or closed depending on the design, but when voltage is applied (under test conditions this is emulated) they must switch.
For posistor relays the technique is simpler: they must have a certain resistance in a cold state (usually from 5 to 50 Ohms). When heated, the resistance increases sharply. You can check this by carefully heating the part with a hairdryer (not with an open fire!) and monitoring the change in the device readings. If the resistance does not change or is zero/infinity, the part is faulty.
Pay special attention to checking the thermal protection. Its contacts should ring when cold (resistance is close to 0). If the circuit is broken, it means that the protection has burned out or is in an open state due to overheating. Let it cool and check again.
Replacement and selection of a new relay
If the diagnostics showed a malfunction, the best solution would be to completely replace the unit. Repair of internal contacts is possible, but is temporary and requires high qualifications. A new relay is inexpensive and guarantees stable operation of the compressor in the future.
When choosing an analogue, be guided not only by the brand of the refrigerator, but also by the marking of the old device. The key parameters are engine power, refrigerant type (R134a, R600a) and compressor type. Often the same relay is suitable for a whole group of models from different manufacturers, for example, universal series relays RT or PZR.
Installation is done in the reverse order. Make sure the contacts are pushed in tightly and all the way. The metal bracket must securely fix the housing so that the vibration of the operating compressor does not break the contact. After assembly, turn on the refrigerator and listen to the first start.
If after replacement the situation has not changed and the compressor hums but does not start, the problem may be deeper - in the engine itself or in the refrigerant circulation system. In this case, you cannot do without the intervention of a specialist and evacuation of the system.
Frequently asked questions
Is it possible to start a refrigerator without a starting relay?
Theoretically, you can apply voltage directly to the starting winding manually for a split second, but this is extremely dangerous and requires experience. Without a relay, the engine will not be able to reach operating mode and will quickly burn out due to overheating of the windings or lack of rotor rotation. Operating a refrigerator without a relay is prohibited.
Why does a new relay burn out immediately after installation?
Most often this happens due to a malfunction of the compressor itself (interturn short circuit, jamming), which consumes a starting current that exceeds the relay rating. Also, the reason may be unstable voltage in the network or incorrect selection of an analogue in terms of power.
How to distinguish a posistor relay from an electromagnetic one?
An electromagnetic relay is heavier, inside you can hear the knocking of the moving core when shaking, and it has a coil. The posistor is lighter, there are no moving parts inside (only the rustling of the crystal is heard), and it works on the principle of changing resistance when heated.
How much does it cost to replace a starting relay?
The cost of the device itself varies from 500 to 2000 rubles, depending on the model and manufacturer. The work of a replacement technician usually costs from 1,500 rubles, but independent replacement takes no more than 20 minutes and does not require special skills other than compliance with safety precautions.