Relay in the refrigerator: what it is and how it works

Many owners of household appliances are faced with a situation where the refrigerator stops freezing, but the light is on inside and clicks are heard. Often the cause of such a malfunction is start-protection relay, which is a critical element of the cooling system. This small device is responsible for starting the compressor engine and protecting it from overloads, acting as a kind of “watchman” of the electrical circuit.

If this component fails, the compressor either does not start at all or works intermittently, which can lead to food damage and costly repairs of the motor itself. Understanding what is a relay in a refrigerator and how it functions will allow you to quickly diagnose the problem and avoid unnecessary costs of calling a technician to simply replace the part.

In this article we will take a detailed look at the structure of the mechanism, analyze its main types, signs of malfunction and features of self-replacement. Knowing these nuances will help you feel more confident when communicating with service departments or when performing repairs yourself.

The principle of operation of the start-up protection device

The main task of this element is to provide a short-term connection to the additional winding of the electric motor when it starts. The fact is that compressor is an asynchronous motor, which requires a powerful starting impulse to start rotating the rotor. Without this impulse, the motor will only hum, trying to move, but will not start.

When the refrigerator is turned on, a current passes through the starting winding, creating a magnetic field. As soon as the engine reaches the required speed (usually this takes a fraction of a second), the device automatically turns off the starting winding, and the motor continues to operate on the main winding. In parallel with this, protective functionis carried out: if the current in the circuit exceeds the norm or the temperature of the windings becomes critical, the relay opens the contacts, stopping the compressor to avoid combustion.

Modern models of refrigerators can use different control circuits, but the physical principle remains similar. It is important to understand that starting relay works under extreme conditions, constantly being exposed to thermal and electrical influences, which over time leads to wear of internal components.

⚠️ Attention: If you hear frequent clicks when the refrigerator is operating, this may indicate an attempt to start and an immediate shutdown protection. Do not ignore this sound, as long-term operation in this mode can damage the compressor.

Main types of relays: thermal and electromagnetic

On the household appliances market you can find two main types of devices, which differ in principle of operation and design. The first type is electromagnetic relays, which were most often installed in older models of refrigerators. Their work is based on the use of an electromagnet, which, at a certain current, attracts the core, closing the contacts of the starting winding.

The second type is thermal (or posistor) relays, which are widely used in modern technology. They are based on a posistor - a ceramic element whose resistance increases sharply when heated. When voltage is applied, the posistor is cold and passes current to the starting winding, then it heats up, the resistance increases, and the current practically stops, opening the circuit.

Each type has its own characteristics of operation and diagnostics. Electromagnetic models are more sensitive to voltage changes, while thermal ones are considered more reliable and durable. However, both of them can fail due to power surges in the network or natural wear and tear of materials.

Below is a table comparing the main characteristics of these devices for a better understanding of their differences:

Typical signs of a relay malfunction

Diagnosis of a malfunction often begins with external observation of the operation of the unit. One of the most striking symptoms is the situation when the compressor is hummingtries to start, but after a few seconds a click is heard and it goes silent. This is a classic sign that the trigger mechanism is not performing its function, and the thermal protection is triggered.

Another sign may be the complete lack of reaction of the refrigerator when plugged in, provided that there is voltage in the socket and the light bulb inside is on. In this case, the motor power supply circuit may be broken due to burnout of the contacts inside the relay or failure of the posistor.

It is also worth paying attention to the appearance of the part itself. If during a visual inspection (after removing the back panel) you notice traces of burning, melted plastic or blackened contacts, then replacement is required immediately. Sometimes the malfunction is accompanied by a specific smell of burnt wiring in the compressor area.

Often users confuse a relay breakdown with a malfunction of the compressor itself. To avoid mistakes, you need to carry out a simple check. If, with a short-term voltage supply directly (which only an experienced master should do), the engine starts and runs, then the problem lies precisely in the starting device.

Diagnostics and performance testing

To accurately determine the malfunction, you will need a multimeter. The first step is to turn off the power to the refrigerator and gain access to the compressor by removing the rear protective panel. Carefully remove the casing from the relay and disconnect it from the compressor contacts.

Checking the electromagnetic relay involves “listening” to the operation of the core. If you shake the relay near your ear, you shouldn't hear any rattling inside (this could mean the core is loose, although this is normal for some models when it's off). A more accurate method is to dial contacts. In the initial position, the contacts of the starting winding should be open, and when turned over (imitation of operation), they should be closed.

Diagnostics positor the relay is even simpler. The posistor must have a certain resistance (usually several tens of Ohms) when cold. If the multimeter shows an open circuit or, conversely, a short circuit (close to zero), then the element is faulty. Also check the integrity of the bimetallic plate of the thermal release.

⚠️ Attention: Before taking any measurements, make sure that the refrigerator is unplugged from the power supply for at least 10-15 minutes. This is necessary to completely discharge the capacitors and cool the thermal elements so that the multimeter readings are correct.

Instructions for replacing the relay with your own hands

If the diagnostics confirm the malfunction, you can proceed with replacement. This process does not require sophisticated equipment, but it does require attention and safety precautions. The main rule is that the new device must fully correspond to the model of the old one in terms of parameters and method of attachment.

First remove the old relay, remembering or photographing which wire is connected where. Usually the wires are color coded, but you shouldn't rely on color alone, as previous craftsmen may have made changes. Disconnect the wires and carefully remove the device from the compressor rod.

Install the new relay into place, firmly pressing it onto the compressor contacts. Connect the wires according to the diagram or photograph you made earlier. Make sure all connections are secure and there is no tension on the wires. After this, install the protective cover and secure the panel.

After assembly, turn on the refrigerator. If the replacement was successful, you should hear a confident start of the compressor, which will turn into a smooth hum without clicks or interruptions. During the first hour of operation, it is recommended to periodically check the heating temperature of the relay itself - it may become warmer, but should not become hot.

Questions and answers (FAQ)