Faced with a situation where the motor-compressor hums, but does not start, or does not show signs of life at all, many owners of household appliances begin to think about independent repairs. Often the cause of such a breakdown is the failure of the starting protection device, which is responsible for starting the engine and protecting it from overloads. Connect the relay to the refrigerator - a task that can be solved for a person with basic electrical skills, but it requires care and strict adherence to safety precautions.
Before you begin Before active actions, it is necessary to completely disconnect the unit from the electrical network. This is not just a recommendation, but a mandatory condition, since working with live conductive elements is deadly. Once the plug is removed from the socket, you should move the refrigerator away from the wall to allow easy access to the compressor located at the lower rear of the cabinet. It is there, on the metal casing of the motor, that the required unit is located.
In this article we will look in detail at how to determine the type of your device, how to dismantle it correctly and, most importantly, how to accurately connect a new or tested relay in place. Understanding the operating principle of this small but critical element will help you not only restore the functionality of your equipment, but also avoid repeated breakdowns in the future.
Diagnostics and types of starting relays
The first stage of work should always be a visual and technical assessment of the condition of the equipment. Starting relays are divided into two main types: induction (electromagnetic) and posistor. Induction models are more often found in old Soviet-made refrigerators or more modern, but budget models. Their principle of operation is based on the closure of contacts under the influence of the magnetic field of the winding when starting the engine.
Posistor relays, or posistors, are more modern and reliable. In them, the role of a switch is performed by a thermistor, which is heated by the passing current and opens the circuit of the starting winding. You can determine the type of device by its appearance: a posistor usually looks like a smaller black plastic cube, while an induction relay often has a more massive body and is heavier in weight.
⚠️ Attention: If you see traces of burning on the relay body, melted plastic or smell burnt insulation, use it it is impossible. Even if the contacts are called by the tester, it is better to replace such a device, since its insulating properties are impaired.
For accurate diagnostics, you will need a multimeter. In the case of a posistor relay, the resistance between the contacts should be within normal limits (usually several tens of Ohms), and when heated, it should go to infinity. Induction relays are checked for open circuits in the coil and for stuck contacts. Incorrect diagnosis can lead to the installation of a serviceable but unsuitable part, which will not solve the problem.
Tools and preparation for work
The quality result directly depends on the preparation of the workplace and the availability of the necessary tools. You don't need complex professional equipment, but a basic home craftsman's kit is required. The main tool will be a multimeter for checking circuits, without which the work will be in the nature of "guessing on coffee grounds."
You will also need screwdrivers (Phillips and flathead), pliers with insulated handles and, possibly, a knife for stripping wires if contact restoration is required. It would be a good idea to prepare isopropyl alcohol or a special contact cleaner to treat connectors before installing a new part.
- 🔧 Multimeter —to check the integrity of the windings and resistance.
- 🪛 Set screwdrivers —to remove protective covers and clamps.
- 🧤 Dielectric gloves —for additional safety when working with electrical appliances.
- 📸 Smartphone —to photograph the connection diagram before disassembly.
It is important to ensure good lighting of the work area. The compressor is often covered with a layer of dust and dirt, so before starting work it is recommended to vacuum or gently wipe the area around the motor so that small particles do not get inside the electrical contacts when opened.
Removing the old relay
The process of removing a faulty device requires care, since the plastic becomes brittle over time. After unplugging the refrigerator and accessing the compressor, you will see a metal casing or plastic box covering the connection point of the wires to the motor. Fastening can be carried out using latches, screws or a spring clamp.
Removing the protective cover, you will see the wires running from the terminal block to the relay contacts. Before disconnecting them, carefully study the diagram. The wires are usually marked with letters or colors, but it is better to double-check the correspondence. Contact group may be covered with oxides, so do not use excessive force so as not to break the wires at the very base.
The relay itself is removed by gently rocking from side to side. It is put on three pins of the compressor. If it is stuck or rusty, you can carefully use pliers, grabbing the metal part, but not the plastic body, so as not to crumble it. After removal, inspect the compressor pins: they should be clean, free of carbon deposits and corrosion.
☑️ Removing the relay
Connection diagram and installation of a new relay
The most crucial moment is connecting a new device. Here it is critical to observe the polarity and assignment of the contacts. The relay body is often marked, but these may not be obvious. The following notation system is usually used: R (Run) - working winding, S (Start) - starting winding, L (Line) - line (phase), M - common.
Posistor relays often have only two or three contacts and are mounted in a specific orientation (arrow up). Induction relays require precise alignment of the contacts with the compressor terminals. If you confuse the working and starting windings, the compressor can hum, overheat and quickly fail, since the starting winding is not designed for long-term operation.
| Designation on the relay | Purpose of contact | Wire color (standard) | Function |
|---|---|---|---|
L or 1 |
Line (Phase) | Red / Brown | Power supply |
R or 2 |
Working winding | Green / White | Main operation of the motor |
S or 3 |
Starting winding | Black / Blue | Engine start |
C or COM |
Common contact | Yellow / Any | Ground/Common |
Connect the wires to terminals of the new relay, making sure that they fit tightly and do not loosen. If the contacts are oxidized, clean them with fine sandpaper or a file until they have a metallic shine. After this, put the relay on the pins of the compressor. It should fit tightly, without play, under its own weight or with light force.
⚠️ Attention: Never try to connect the relay “on weight”, simply holding it in your hand to check operation. This is a gross violation of safety regulations. All connections must be fixed in the normal position.
Checking the system's functionality
After installing all the elements in place and returning the protective casing, you can begin testing. Plug in the refrigerator. In the first seconds you can hear a characteristic click - it works starting relay, starting the compressor. If the engine starts smoothly, without humming or vibration, and after some time cold begins to appear in the chamber, then the replacement was successful.
However, if the compressor hums but does not start, or a click is heard immediately and the motor goes silent, then the problem may be deeper. Perhaps the compressor itself is faulty (turn-to-turn short circuit) or the new relay is selected incorrectly. It is also worth checking the thermostat: if it is open, the voltage simply will not flow to the relay.
What to do if the compressor hums but does not start?
If after replacing the relay the motor hums and clicks, but does not spin, the compressor may be jammed. In some cases, briefly applying voltage to the starting winding through a capacitor helps, but this is a risky procedure that requires skill. Most often, this is a sign that the compressor needs to be replaced.
Pay attention to the heating of the relay during operation. After 15-20 minutes of operation it should not be hot. Only light heat is allowed. If the relay housing melts or sparks, turn off the unit immediately. This may indicate poor contact in the terminal block or a mismatch in the parameters of the motor power relay.
Frequent errors and expert advice
When doing self-repair, beginners often make common mistakes that can ruin all efforts. One of the most common is ignoring the relay orientation. Many models, especially posistor ones, are sensitive to position in space. If there is an arrow on the case with the inscription UP or TOP, it should look straight up.
Another mistake is using a relay from another refrigerator model “by eye.” Externally, they may be identical, but have different current characteristics. The relay operation current must strictly correspond to the power of your compressor, otherwise the protection will either not work during an overload, or will knock out at every start.
- ⚡ Do not ignore the condition of the wires: if the insulation is cracked, replace the entire section of the cable, and don’t just wrap it with electrical tape.
- 🧊 Check not only the relay, but also the thermostat: often they fail at the same time due to power surges.
- 🔌 Make sure that the plug and socket are working: a bad contact in the network can simulate a relay failure.
It is also worth remembering that the compressor must cool down between starting attempts. If you have performed several tests, let the equipment stand turned off for 30-40 minutes. This will allow the oil to drain into the crankcase, and the posistor in the relay to cool and restore resistance.
⚠️ Attention: Technical characteristics of compressors and relays may vary depending on the manufacturer and year of manufacture. Always check the markings on the motor nameplate with the parameters of the new relay before purchasing and installing.
Is it possible to short-circuit the relay to start the refrigerator?
There is a “direct feed” method when the relay is excluded from the circuit. This can only be done to diagnose the compressor for a few seconds. Leaving the refrigerator to operate without a relay is STRICTLY PROHIBITED: the starting winding will burn out, and the compressor will have to be thrown away.
Questions and answers (FAQ)
How to understand that it is the relay that has burned out, and not the compressor?
If the compressor is silent, but The light in the refrigerator is on, ring the motor windings through the relay contacts. If the resistance of the windings is normal (not zero or infinity), and when voltage is applied to the relay, a click is heard, but there is no start, most likely the problem is in the relay or the start circuit. If the windings ring short or are broken, the compressor is faulty.
Is it possible to use a relay from another brand?
Yes, you can, if the main parameters match: type (posistor/induction), voltage (220V), number of contacts and, most importantly, operating current. Universal relays often come complete with adapters for different types of compressors.
Why does the new relay click, but the refrigerator does not freeze?
This may indicate several problems: the wires are connected incorrectly (the windings are mixed up), the thermostat is faulty (does not give a start command), or the compressor itself is mechanically jammed. It is also possible that there is no freon in the system, and the motor is idling, although the relay is triggered.
How long does the starting relay last?
The average service life of a high-quality relay is 5-10 years, but it greatly depends on the stability of the voltage in the network and the number of on/off cycles of the refrigerator. Frequent voltage drops significantly reduce the service life of the part.