The refrigerator has stopped freezing, and instead of the usual hum, you hear only a quiet click, followed by a hum, quickly followed by silence? This is a classic scenario indicating a problem in the compressor motor starting circuits. In 80% of cases, the culprit for this behavior is a small but critical component - the start relay. It is this that is responsible for supplying voltage to the motor windings at the time of start.
Understanding this how a relay works on a refrigeratorallows you not only to save on calling a technician, but also to carry out initial diagnostics yourself. This mechanism is an electromagnetic switch that closes the starting winding circuit for only a fraction of a second, helping the rotor gain speed. If this process is disrupted, the compressor either does not start at all or operates with overload, which can lead to its complete failure.
In modern models, such as Indesit or Atlant, different types of these devices are used, but the physics of the process remains the same similar. We will analyze the internal structure, causes of burnout and testing methods so that you can accurately determine the condition of the unit.
Purpose and role in the starting system
The main task of the starting relay is to provide a short-term connection to the starting winding of the asynchronous compressor motor. When the refrigerator is turned on, the rotor is at rest, and significant force is required to move it from a dead point. The main torque of the working winding is not enough, so an auxiliary circuit comes into play, the control of which is taken over by the relay.
As soon as the engine reaches about 75% of the rated rotation speed, the relay should automatically break the starting winding circuit. If this does not happen, the current in the winding will increase to critical values, which will lead to overheating and burning of the insulation. Thus, the device performs a double function: it helps to start the motor and protects it from abnormal operation.
Modern systems often integrate a thermal protection relay into the same housing as the starting one. This compact solution allows you to monitor the temperature of the coils and open the power circuit in the event of overcurrent. In models Beko and LG such combined units are most common, which simplifies the design, but requires replacing the entire unit if any of the elements fail.
⚠️ Attention: Before any intervention in the electrical circuit of the refrigerator, be sure to disconnect the appliance from the network. Residual voltage on the capacitors or in the compressor circuit can lead to an electric shock even after unplugging from the outlet.
Design features and types of devices
There are two main types of starting relays used in household refrigeration equipment: posistor (solid-state) and electromagnetic. PTC models, often found in refrigerators, do not have moving contacts. Their work is based on the property of a semiconductor material (posistor) to sharply increase resistance when heated. Samsung And Whirlpool, do not have moving contacts. Their work is based on the property of a semiconductor material (posistor) to sharply increase resistance when heated.
When voltage is applied, a cold posistor has a low resistance, passing current through the starting winding. The passing current heats the crystal, its resistance increases hundreds of times, and the current practically stops. This process takes a few seconds. After cooling (it takes 3-5 minutes), the posistor is ready for use again. The absence of mechanical parts makes them reliable, but sensitive to voltage drops. Electromagnetic relays, typical of older models, operate on the solenoid principle. The current passing through the coil creates a magnetic field that draws in the core and closes the contacts. When the motor accelerates, the current drops, the spring returns the core, and the circuit opens. Such devices have moving parts that can stick or burn over time.
Electromagnetic relays typical of older models ZIL or Biryusa, work on the solenoid principle. The current passing through the coil creates a magnetic field that draws in the core and closes the contacts. When the motor accelerates, the current drops, the spring returns the core, and the circuit opens. These devices have moving parts that can stick or burn over time.
What is the difference between RTP and RTK relays?
RTP relays (posistor) operate from heat and do not make clicking sounds during operation, only when cooling. RTK (electromagnetic) relays emit a distinct click when the contacts open during each startup cycle. RTKs often require an exact position during installation (arrow up).
Symptoms of a faulty starting relay
You can determine that the relay has failed by the characteristic signs that appear immediately after the device is turned on to the network. Most often, the owner hears a series of clicks at intervals of several minutes. This triggers thermal protection: the compressor tries to start, the relay does not work, the current increases, and the thermal relay opens the circuit.
Another striking symptom is the smell of burning or melted plastic in the compressor area. If the relay is stuck in the closed state, the starting winding continues to heat up, which can lead to a fire hazard. In such cases, traces of soot or plastic deformation are often visible on the relay body.
Sometimes the refrigerator may work, but intermittently. The engine hums, but does not start, or starts jerkily. This may indicate that the contacts inside the relay are burnt and have a poor connection, or the posistor has lost its properties and does not provide sufficient current to start.
- 🔊 Frequent clicks: repeated every 2-5 minutes without starting the compressor.
- 🔥 Housing heating: the area near the compressor becomes hot for touch.
- 🛑 Lack of cold: the chamber does not cool, although the light inside is on.
- 🌫️ Smell burning: a clear sign of overheating of the insulation or contacts.
Checking and diagnostic algorithm
For accurate diagnostics, it is necessary to remove the relay from the refrigerator. It is usually mounted on the side of the compressor and secured with a bracket or plastic holder. After removing the device from the motor contacts, it should be inspected for external damage: cracks, blackening, melting.
Checking the posistor relay is carried out with a multimeter in resistance measurement mode. In a cold state, the resistance between the terminals should be low (tens of ohms). If the device shows infinity or one, it means that the posistor has burned out and requires replacement. You can ring it by connecting the probes to the contacts.
The electromagnetic relay is checked visually and by ear. If you shake the device and you hear the sound of a detached core or contacts, it must be replaced. The integrity of the solenoid coil is also checked - the resistance must be within the normal range specified in the technical documentation for the specific model.
☑️ Diagnostics of the refrigerator relay
It is important to check not only the relay itself, but also the state of the contacts on the compressor. If the pins are oxidized or covered with carbon deposits, even a working relay will not be able to provide a reliable start. Cleaning the contacts with fine sandpaper or a file often solves the problem of unstable operation.
Table of common faults
Below is a summary table that will help compare the symptoms with the probable cause of the breakdown. This will simplify the search for a defect and allow you to make the right decision on repairs.
| Symptom | Probable cause | Solution method |
|---|---|---|
| Clicks, the compressor hums for 5-10 seconds and turns off | The starting relay is faulty or the compressor is jammed | Replacing the relay, checking the compressor |
| The refrigerator is silent, there is no light | No power, the thermal relay is burned out | Checking the socket, replacing the thermocouple |
| The compressor runs continuously without turning off | Relay contacts are stuck in the closed state | Urgent replacement of the start relay |
| A cracking sound is heard inside the relay during operation | Burning of contacts, poor contact | Replacing the device |
⚠️ Attention: Do not try to start a refrigerator with a faulty relay “directly”, bypassing the protection. This is guaranteed to lead to burning of the compressor windings, the cost of replacing which is not comparable to the price of a new relay.
Replacement and selection of analogues
When purchasing a new relay, it is important to consider not only the brand of the refrigerator, but also the power of the compressor. The device body usually has markings, for example, PTM-11C or R-6. The numbers in the name often indicate the rated current or power of the motor for which the relay is intended.
The replacement process is simple: the new device is put on three contacts of the compressor (common, starting, working). It is important to maintain the correct orientation, especially for electromagnetic models where the arrow pointing up position is indicated. Incorrect installation may result in the core not falling under the influence of gravity and the circuit not opening.
For models Stinol and Indesit universal kits are often used, which include the relay itself, thermal protection and connecting wires. This allows you to replace the entire group of contacts at once, eliminating the risk of poor connections in old terminals.
Prevention and service life
The service life of the starting relay directly depends on the stability of the voltage in the electrical network and the frequency of switching on the refrigerator. Voltage surges are the main enemy of posistors. To extend the life of equipment, it is recommended to use surge protectors or voltage stabilizers, especially in the private sector or old houses.
It is also important to ensure good ventilation of the compressor. If the refrigerator is located close to a wall or in a niche, overheating of the motor area can be transmitted to the relay, changing its characteristics. Regularly cleaning the rear grille of dust helps maintain optimal temperature conditions.
If you notice that the refrigerator is starting to turn on more often than usual, this may be a sign of problems with the thermostat or door seal. Frequent starts wear out the starting relay faster, since each start puts a load on the contacts and the posistor. Timely elimination of the causes of frequent cycling will extend the life of the entire unit.
Is it possible to repair a burnt-out relay?
Theoretically, an electromagnetic relay can be disassembled and the contacts can be cleaned, but this is a temporary measure. PTC relays cannot be repaired, since the crystal changes its properties irreversibly. Considering the low cost of a new part, repairing an old relay is not economically feasible.
Why does the relay click, but the compressor does not start?
This means that the control circuit is working, but the starting pulse does not pass through or is not enough to shift the rotor. Reasons: the posistor burned out (no resistance), the contacts burned (no contact) or the compressor itself jammed (mechanical failure).
Does the room temperature affect the operation of the relay?
Yes, posistor relays require time to cool down (3-5 minutes) before turning on again. If the room is very hot, the cooling time will increase. An attempt to turn on the refrigerator immediately after turning it off may not produce results until the posistor has cooled down.
Which brand of relay is best to buy?
It is best to look for original spare parts with the manufacturer's markings (Danfoss, Secop). However, high-quality universal analogues from trusted brands (for example General Electric or specialized brands of spare parts) often work no worse than the originals with the correct selection of power.