The situation when the refrigerator stops cooling, and only a quiet hum or a characteristic click is heard from the engine compartment, familiar to many owners of household appliances. At this moment, the compressor tries to start, but start-up protection relay does not perform its function, opening the circuit and cutting off the voltage supply to the motor windings. This is a protective mechanism that prevents the burning of an expensive motor in the event of a malfunction in the electrical network or internal problems of the unit itself.
Ignoring such a breakdown can lead to serious consequences, including failure of the compressor, the replacement of which is often not economically feasible. Understanding how this small but critical component works will help you diagnose the problem faster. In most cases, we are talking about natural wear of the bimetallic plate or burning of the contacts, which requires the intervention of a specialist or careful independent replacement.
In this article we will analyze in detail the design of various types of relays, a troubleshooting algorithm and step-by-step instructions for restoring the functionality of the refrigerator. It is important to notethat any work with electrical appliances requires compliance with safety precautions, therefore, before starting diagnostics, it is necessary disconnect the device from the network.
The principle of operation of the start-up protection relay
The start-up protection relay is an electromechanical device that automatically supplies voltage to the starting winding of the compressor only at the moment of startup. As soon as the engine rotor reaches the required speed, the relay opens the starting winding circuit, leaving only the main winding running. In parallel with this, it performs a protective function: if the current in the circuit exceeds the norm or the motor overheats, the device breaks the contact, preventing an emergency.
There are two main types of such devices, which differ in the principle of operation and design. Start relays they work on the basis of the electromagnetic principle: the current passing through the coil creates a magnetic field that draws in the core and closes the contacts. Thermal (protective) relays react to an increase in temperature or current, using the properties of the bimetallic plate to bend when heated and open the circuit.
In modern refrigerators, such as Indesit, Atlant or LG, combination devices are often used that combine both functions in one housing. They are attached directly to the compressor output contacts or near it in the engine compartment. The reliability of the entire system directly depends on the condition of the contacts and the integrity of the internal elements.
⚠️ Attention: Inside the relay, residual voltage or charge may remain in the capacitors (if they are present in the control circuit). Before touching any metal parts, make sure that the refrigerator is unplugged from the outlet for at least 10-15 minutes.
Incorrect operation of this unit often manifests itself in cyclical attempts to start: you hear a click, the motor hums for a couple of seconds, then another click and silence follows. This is a classic sign that starting winding is not receiving a pulse or the current in the circuit is growing too quickly, causing the protection to operate instantly.
Why are relays called "hot" or "cold"?
In a professional environment, relays are divided into “hot” (thermal, triggered when the plate is heated) and “cold” (electromagnetic, triggered instantly when current is applied). Modern combined devices are often called simply PZR (start-up protection relay).
Main symptoms of relay malfunction
It is possible to determine that the problem lies in the relay by a number of characteristic signs that appear in the operation of refrigeration equipment. The first and most obvious symptom is the lack of cold in the cells when the lighting is on. In this case, the compressor can either be silent or make short humming sounds, interrupted by clicks.
If you observe that the motor is trying to start, but immediately stops, this indicates that protective mechanism an overload is detected. In some cases, the housing of the relay or compressor itself may become very hot, which is also an alarming signal. If operated for a long time in this mode, the engine may burn out.
Another sign may be visual damage: if you remove the relay cover, you may find melted contacts, blackening of the plastic, or traces of burning. This indicates that the device was operating in extreme mode or a short circuit occurred. Also, a malfunction may be indicated by the smell of burnt wiring coming from the engine compartment.
- 🔊 Characteristic clicks: Regular sounds of switching on and off every few minutes without switching to operating mode.
- 🌡️ Overheating: Excessive increase in the temperature of the rear wall or the compressor itself in a short time.
- 💡 No starting: The light in the refrigerator is on, but the engine is completely silent, not even making a hum.
- ⚡ Knocking out plugs: In rare cases, a faulty relay can cause a short circuit, leading to the operation of the circuit breakers in the panel.
It is important to distinguish a relay breakdown from a malfunction of the compressor or thermostat itself. If, when plugged in, the engine makes a loud hum and after 5-10 seconds a shutdown click is heard, most likely the problem is in the starting mechanism or jamming of the piston group.
Diagnostics and testing with a multimeter
To accurately determine the cause of the failure, it is necessary to carry out instrumental diagnostics using multimeter. This device will allow you to measure the resistance of the windings and the integrity of the relay contacts, which will give an unambiguous answer about its performance. Before starting the test, be sure to remove the relay from the compressor, having first photographed the connection diagram.
The first step is to check the integrity of the bimetallic plate and coil. In a thermal relay, the resistance should be close to zero (short circuit), since in a cold state the contacts are closed. If the device shows infinity (OL or 1), it means that the circuit is open and the relay is faulty. In electromagnetic relays, the resistance of the coil is checked, which is usually several tens of ohms.
Next, you need to “ring” the contacts that go to the starting winding. Depending on the type of device, their resistance should also be minimal. If the contacts are burnt, the resistance may be unstable or too high, which will not allow sufficient current to pass to start the engine.
Normal resistance values (approximate):- Thermal protection: 0 Ohm (closed)
- Solenoid coil: 10-50 Ohm
- Starting contacts: 0 Ohm
- Resistance of the compressor windings: 10-40 Ohms (depending on the model)
Don't forget to also check the resistance between the relay body and the contacts - it should be infinite. The presence of conductivity indicates an insulation breakdown, which makes further operation of the device dangerous to life.
Table of typical faults
To systematize data on possible problems, we will compile a summary table. It will help you quickly compare the symptoms with the probable cause and choose the right solution. Remember that the diagnosis must be comprehensive.
| Symptom | Probable cause | Action | Difficulty |
|---|---|---|---|
| Clicks, the engine does not start | Faulty starting relay | Replace the relay | Low |
| Humming and shutdown after 10 seconds | Stuck compressor or relay | Checking the compressor | High |
| The refrigerator is silent | Open circuit in the protection circuit | Test with a multimeter | Average |
| Smell of burning, blackening | Short circuit in the relay | Urgent replacement | Low |
Analyzing the table data, we can conclude that most problems can be solved by replacing an inexpensive component. However, if the reason lies in the compressor itself, repairs may require specialized equipment and skills.
Often users confuse a relay failure with a thermostat failure. To eliminate this option, you can close the thermostat contacts directly (for a short time to check). If the refrigerator starts working, then the relay and motor are working, and the problem is in the temperature sensor.
Instructions for replacing the start relay
Replacing the relay is a procedure that is accessible even to beginners, if you act carefully and consistently. The main rule: the new part must completely match the model of the old one. Parameters may differ even for externally identical devices, therefore marking on the case is a key point of reference when purchasing.
First, remove the back panel of the refrigerator to gain access to the compressor. Disconnect the wires going to the relay and carefully remove the part itself from the contact group of the compressor. It may fit tightly, so rock it slightly from side to side, avoiding sudden jerks, so as not to damage the tubes.
Install the new relay in the same position in which the old one was (usually indicated by an arrow UP or TOP). Connect the wires according to the diagram or color coding. After assembly, plug in the refrigerator and listen: if after a few seconds you hear the confident sound of the motor running and the cold starts, the repair was successful.
☑️ Algorithm for replacing the relay
After replacement, it is recommended to observe the operation of the unit for 30-60 minutes. The compressor must operate cyclically: turn on, cool the chamber, turn off when the set temperature is reached and turn on again after a certain period of time.
The influence of voltage drops and the external environment
A frequent cause of failure of start-up relays is unstable parameters of the electrical network. Voltage surges, especially in rural areas or residential buildings, lead to overheating of the bimetallic plate and burning of the contacts. Under such conditions, the relay operates more often than expected, which accelerates its wear.
The operation of the device is also negatively affected by the high temperature in the room where the refrigerator is installed. If the engine compartment is poorly ventilated or the refrigerator is placed close to a wall, heat will not be dissipated effectively. This leads to the fact that thermal protection is triggered even when the compressor is working, considering overheating to be an operating situation.
⚠️ Attention: Do not install the refrigerator in niches without ventilation and near heat sources (radiators, stoves). This shortens the service life of not only the relay, but also the insulation of the compressor windings.
To protect equipment in conditions of unstable power supply, it is recommended to use voltage stabilizers or surge protectors with a surge protection function. This will extend the life of the electronics and mechanical components of your refrigerator.
Frequently asked questions (FAQ)
Is it possible to start a refrigerator without a relay?
Theoretically, you can start the compressor by applying voltage directly to the starting winding through a button, but this is extremely dangerous and requires qualifications. Without a protective relay, the compressor will burn out at the first overload or jam. It is strictly prohibited to operate a refrigerator without a relay.
Why does the new relay burn out immediately after installation?
If the new relay burns out instantly, the reason is not in it, but in the compressor. Most likely, there was an interturn short circuit in the motor windings or a mechanical wedge. In this case, the starting current exceeds the norm by several times, which leads to rapid destruction of the contacts of even a new relay.
How to choose an analogue if the original is not on sale?
Look for a relay with similar electrical characteristics (starting current, compressor type) and geometric fit. Universal relays often have additional wires or adapters. The main thing is matching the power and type (regular relays are not suitable for inverter compressors!).
Is it possible to repair an old relay by cleaning the contacts?
A temporary measure that rarely gives a long-term effect. Cleaning the contacts with sandpaper may help for a couple of days, but the disturbed calibration cut-off current and metal fatigue of the bimetallic plate will not go away. It is safer and more reliable to buy a new part.