A sudden stop of the refrigerator is always stressful, because food supplies and comfort are at risk home. Often the cause of the breakdown is not the engine itself, but a failed trigger mechanism, which is responsible for starting the engine. If you hear that the motor is humming, but does not start, or, on the contrary, it clicks and immediately goes silent, then in 80% of cases the problem lies precisely in the starting-protective relay. compressor, but a failed trigger mechanism, which is responsible for starting the engine. If you hear that the engine is humming but does not start, or, conversely, it clicks and immediately goes silent, then in 80% of cases the problem lies in the start-protective relay.
Independent diagnostics of this unit allows you to save a significant amount on calling a technician, since the verification procedure is quite simple and does not require complex equipment. Start relay is a small block mounted on the side or bottom of the compressor, and its main task is to briefly apply current to the starting winding of the engine to create torque. Understanding the operating principle of this element will help you quickly determine whether you need to buy a new part or look for a deeper problem.
Before starting disassembly, you need to turn off the power to the unit and prepare the basic tool. In this article we will look in detail at how to visually assess the condition of the contacts, how to test the windings with a multimeter and what to look for when choosing a replacement. Correct diagnostics will eliminate the risk of buying unnecessary spare parts and will allow you to return the equipment to life in a matter of minutes.
Signs of a faulty starting relay
You can determine that the relay has failed by its characteristic sounds and behavior compressor. Most often, owners notice that the refrigerator has stopped freezing, although the light inside is on. The compressor may try to start by making a loud beeping noise, but after a few seconds there is a clicking sound and the engine stops talking. This is a classic symptom that starting winding does not receive the required impulse or the thermal protection is triggered.
In some cases, the malfunction manifests itself differently: the motor runs continuously without turning off, which leads to excessive cooling or, conversely, overheating of the housing. If the relay is “stuck” in the closed state, current continues to flow to the starting winding, which can lead to engine combustion. It is also worth paying attention to the appearance of the part: the presence of carbon deposits, melted plastic or a burning smell clearly indicate the need for replacement.
⚠️ Attention: If, after clicking the relay, the compressor buzzes for more than 10-15 seconds and does not start, immediately unplug the refrigerator. Long-term operation in this mode (“hard start”) can permanently damage the motor windings.
For a more accurate understanding of the symptoms, compare the behavior of your refrigerator with typical signs of breakdowns in the table below:
| Symptom | Probable reason | Action |
|---|---|---|
| Humming and clicking, no start | The starting relay is faulty or the compressor is jammed | Checking the relay with a multimeter |
| The motor runs constantly | Relay contacts are stuck in the closed state | Replacing the relay |
| The refrigerator does not turn on at all | Open circuit in the thermal relay or thermostat | Power circuit continuity |
| A cracking sound is heard inside the relay housing | Mechanical destruction of the core or contacts | Visual inspection and replacement |
The design and principle of operation of the relay
To effectively check the part, you need to understand how it works arranged. In modern household refrigerators, starting relays are most often used. They work on the principle of a solenoid: when voltage is applied to the main winding of the motor, current passes through the relay coil, creating a magnetic field. This field draws in the core, which closes the contacts of the starting winding, allowing the compressor rotor to gain speed. electromagnetic starting relays. They work on the principle of a solenoid: when voltage is applied to the main winding of the motor, current passes through the relay coil, creating a magnetic field. This field draws in the core, which closes the contacts of the starting winding, allowing the compressor rotor to gain speed.
As soon as the engine reaches its rated speed, the current in the circuit drops, the magnetic field weakens, and the core, under the influence of gravity (or a spring), returns to its original position, opening the starting circuit. In parallel with the starting one, there is often a built-in thermal relay (protection), which opens the circuit when the compressor overheats or when the current consumption is too high. In older models, there may be posistor relays, where the role of a switch is performed by a heating element, but the diagnostic principle is similar for them.
What is the difference between a posistor and electromagnetic relay?
Electromagnetic relays operate due to the magnetic field of the coil and have a movable core, which makes a characteristic click. Posistor relays do not have moving parts - they use a crystal (posistor), which, when heated by current, sharply increases its resistance, opening the circuit. The posistor ones are considered more reliable, since there is nothing to mechanically break in them, but they require time to cool down (3-5 minutes) before restarting.
It is important to note that the relay is designed to operate in a certain current range. If the compressor is worn out and drawing too much current, the thermal protection will continually cut off the power, simulating a failure of the relay itself. Therefore, when diagnosing, you should always take into account the condition of the unititself. Different manufacturers, such as Indesit, Atlant or Bosch, may use relays of different designs, but the physics of the process remains the same.
Dismantling and visual inspection of the part
The first stage of testing is removal relay from the refrigerator body. To do this, you need to disconnect the appliance from the mains and gain access to the compressor, which is usually located in the lower rear part of the case. Sometimes it is necessary to remove a protective cover or cardboard panel. The relay is placed directly on the compressor terminals and secured with a bracket or plastic latches.
Carefully remove the retaining bracket and pull the relay off the contacts. Be careful: the wires may be short, so don't pull too hard. Before picking up the multimeter, perform a thorough visual inspection. Look for signs of soot, melted plastic, swelling of the case, or oxidation of the contacts. If you see black spots inside the relay body or smell burnt insulation, further inspection may not be necessary - the part is definitely faulty.
☑️ Visual inspection checklist
Particular attention pay attention to labeling. The relay body is marked with a connection diagram and technical characteristics, such as operating current and type of refrigerant. This data is critical when selecting a replacement. If the markings are erased or the housing is damaged so much that the inscriptions are (not visible), it is better to photograph the model of the refrigerator and compressor to search for an analogue in catalogues.
Checking the relay with a multimeter
The most accurate diagnostic method is to use a tester (multimeter) in resistance (Ohm) measurement mode. Before starting measurements, make sure that the relay has completely cooled down, especially if it is a posistor type. For electromagnetic relays, testing consists of “continuity testing” of the circuits between the contacts. You need to find the contacts of the main winding, starting winding and power input.
Take the tester probes and touch them to the corresponding pairs of contacts. In normal condition, the resistance between the input and the main winding contact should be close to zero (the circuit is closed). The resistance between the input and the start contact should also be minimal if the relay is healthy and in the quiescent state (for some types). If the tester shows one or infinity where there should be zero, then the contact is broken. If it shows zero where there should be a break, the contacts are stuck.
Separately, it is worth checking the thermal relay if it is built into a common housing. It should “ring” when cold (resistance close to 0 Ohm). If the circuit is open even when the relay is cold, it means the thermal protection has burned out. Also check the integrity of the windings of the compressor itself through the contacts on the relay to prevent motor breakdown.
⚠️ Attention: When checking with a multimeter, never touch the probes with your hands at the same time as the metal contacts of the relay. Although a voltage of 9-12 volts from the probes is safe, you can introduce an error into the resistance measurements of your body, which will distort the readings of the device.
Table of typical resistance values
For ease of interpretation of measurement results, we provide approximate values. Keep in mind that the exact numbers may depend on the compressor capacity and the type of relay. Basic rule: the resistance of the starting winding is always higher than the resistance of the working winding.
| Pair of contacts | Normal reading | Fault |
|---|---|---|
| Input - Working winding | 10 - 30 Ohm | Infinity (open) or 0 (short circuit) |
| Input - Start winding | 30 - 80 Ohm | Infinity (break) |
| Working - Start winding | Sum of resistance | Short circuit to housing |
| Thermal relay contacts | 0 - 1 Ohm (on cold) | Infinity (burnt out) |
If the multimeter readings are very different from the norm, or the device does not respond at all, the relay must be replaced. Do not try to repair the insides of the relay - this is a sealed or complex assembly, the restoration of which does not guarantee long-term operation.
Replacing and installing a new relay
Purchasing a new part is the most reliable way to solve the problem. When choosing, pay attention not only to compatibility with the refrigerator brand, but also to the compressor power (indicated in horsepower or watts) and the type of refrigerant (R134a, R600a). Installation is carried out in the reverse order of removal: first we put the relay on the compressor terminals, then we fix it with a bracket and connect the wires.
It is important to orient the relay correctly: there is usually an arrow or inscription on the body UPthat should look up. This is critical for electromagnetic models where the core must move under the influence of gravity. If you confuse the orientation, the compressor simply will not start.
After installation, turn on the refrigerator and listen. The compressor should start with a characteristic hum, after a few seconds the click of the relay will turn off the starting winding, and the motor will switch to smooth operation. If after 5-10 minutes the compressor housing does not heat up excessively, and cold begins to appear in the chamber, the repair can be considered successful.
Frequent errors in diagnostics
Many amateur repairmen make typical mistakes that lead to false conclusions. For example, trying to clean the contacts inside the relay with sandpaper. This breaks the special coating of silver or other alloys, and after a short time the relay burns out again. In addition, disassembling the sealed housing often leads to its damage.
Another mistake is ignoring the condition of the compressor. If the motor is mechanically jammed, even a working relay will click, but will not be able to start it. In such cases, an attempt to run the compressor through a capacitor (a method popular among the Kulibins) can finish off the windings. Always check the free play of the compressor shaft (if there is access) and the resistance of the windings.
Is it possible to use a relay from another refrigerator?
You can use an analogue, but only if the characteristics completely match. Key parameters: operating current (Ampere), type of refrigerant, contact location and overall dimensions. A relay from a powerful two-chamber refrigerator will not fit a small single-chamber refrigerator, and vice versa - this will either lead to underheating of the starting winding or to its combustion.
Why does a new relay burn out after a week?
If replacement does not solve the problem for a long time, the reason lies in the compressor itself. Wear of the mechanical part leads to an increase in starting currents, the thermal relay heats up and turns off the motor. Constant on-off cycles destroy the contacts of the new relay. In this case, professional repair or replacement of the compressor is required.
Is it dangerous to operate a refrigerator without a relay?
It is absolutely not possible. Without a start relay, the compressor will not be able to start on its own and will hum, consuming huge current, which will lead to a fire or melted wiring. Without a thermal relay, the engine will burn out under any overload, since it will not have protection against overheating.