A sudden stop of the compressor or a characteristic click, after which the refrigerator goes silent, often indicates a malfunction of the start relay. This small but critical element is responsible for starting the motor and protecting its windings from overloads. Owners of household appliances are often faced with the need to replace a failed device, but the process of installing it requires care and adherence to a strict procedure, since incorrect connection can lead to combustion of the compressor.
Before proceeding with the physical connection of the contacts, it is necessary to completely de-energize the unit and gain access to the motor located in the lower rear part of the case. Safety here is a priority number one, therefore any manipulations with electrical circuits are carried out only after removing the plug from the socket. It is important to understand that the connection diagram may vary depending on the manufacturer of the compressor and the type of the relay itself, be it a posistor device or a model with an inductance coil.
In this article we will analyze in detail the algorithm of actions that will allow you to independently and competently replace the starting relay. We will look at the color coding of wires, the features of connecting various types of contacts, and typical mistakes that inexperienced craftsmen make. Correct installation will ensure stable operation of the refrigeration unit and extend the service life of its main unit.
Diagnostics and preparation for replacing the relay
The first stage of work is a visual inspection and preliminary diagnostics. Often the problem lies not in the relay itself, but in oxidized contacts or broken supply wires. Remove the protective cover from the compressor and carefully remove the relay. If traces of burning, melted plastic, or the smell of burnt insulation are visible inside the housing, then replace the element required. It is also worth checking the integrity of the suitable wires, since the vibration of the compressor can lead to their fracture over time.
To carry out the work, you will need a minimum set of tools: pliers, a screwdriver with an insulated handle and, preferably, a multimeter to check the integrity of the circuits. Before disconnecting the old wires, it is highly recommended that you take a photo of the current wiring diagram. This will help avoid confusion, especially if the color markings on the wires have worn off or are not standard.
⚠️ Warning: Never attempt to start the compressor with open contacts or a removed relay. This may result in a short circuit, electric shock, or permanent damage to the motor windings.
If you plan to use a used relay for testing, make sure it matches your compressor model exactly. There are no universal solutions here: the parameters of the starting current and the protection response time must strictly correspond to the characteristics of the motor. A discrepancy can lead to the compressor either not starting or operating in emergency mode, quickly wearing out.
Types of starting relays and their features
Understanding the relay structure helps to correctly navigate the connection diagram. There are two main types of devices used in modern and old refrigerators: posistor and induction (electromagnetic). Posistor relay does not have moving contacts in the classical sense; the starting winding is connected through a thermistor, which, when heated, sharply increases the resistance, opening the circuit. Such devices usually have three or four contacts and are connected directly to the compressor terminals.
Inductive relays operate on the principle of an electromagnet. When voltage is applied, current passes through the coil, the created magnetic field draws in the core, which closes the contacts of the starting winding. After the engine starts, the current drops, the spring returns the core, and the circuit opens. In such models, it is important not to confuse the installation position, since they are sensitive to orientation in space (often marked “UP” or an arrow).
Is it possible to use a relay from another brand?
In most cases, it is possible if the electrical characteristics (rated current, type of connection) and the geometric dimensions of the seat match. However, it is better to look for original spare parts or complete analogues recommended by the compressor manufacturer in order to avoid problems with the operation of the thermal protection.
Thermal protection, which is often built into the relay housing or mounted nearby, deserves special attention. It is responsible for turning off the power when the compressor overheats. When replacing a relay, the thermal relay is often also replaced, since their service life is approximately the same. The serviceability of the thermal relay is checked by checking the contacts: in a cold state they should ring, and when heated (if it is possible to check) they should open.
Wire connection diagram: color marking
The most difficult moment for beginners is identifying the wires. Standard color coding helps you figure out which wire is connected where, but you should always check the diagram on the compressor body or in the technical documentation. Typically, three main wires are suitable for the relay: phase, neutral and ground, as well as wires going directly to the motor windings.
Consider the standard layout for most European and many Asian models of refrigerators:
- 🟢 Green (or yellow-green) wire is grounding. It connects to the metal body of the compressor or a special ground terminal, ensuring the safety of the user.
- 🔵 Blue (or white/black depending on the region) is the neutral wire (N). It goes directly to one of the motor windings.
- 🟤 Brown (or red/black) is the phase wire (L). It approaches the thermal relay, and then is distributed to the starting and operating windings through the relay contacts.
On the relay itself, the contacts are also marked. The following designations are often used: L (line/phase), N (neutral), R (working winding), S (starting winding). In some models, there may be numbers or symbols instead of letters. It is critically important not to confuse the contacts of the starting (S) and working (R) windings, as this will lead to the hum of the motor without starting and rapid burnout of the windings or the relay itself.
If the markings on the wires are missing or colors non-standard, use a multimeter in dialing mode. The resistance between the common contact and the working winding is always less than that between the common contact and the starting winding. The resistance between the starting and working windings is equal to the sum of the two previous values.
Step-by-step instructions for connecting
The process of connecting a new relay requires accuracy and consistency. First, install the thermal relay on the compressor terminals, if it is made in the form of a separate tablet placed on the contacts. Then the starting relay itself is put on the compressor terminals. It should fit tightly, without play, but also without excessive force, which could damage the ceramic terminal insulators.
Next, we proceed to connecting the wires to the relay terminal block. Use a previously prepared photograph or diagram. The wires are inserted into the appropriate sockets and fixed. Some models simply pull the wires onto pins, while others require tightening screws or using crimp terminals. Make sure that the insulation of the wires does not get inside the contact, and the bare part is completely inserted into the socket.
☑️ Check before turning on
After connecting all the wires, check the reliability of the connections by lightly pulling each wire. Lay the wires so that they do not touch the hot parts of the compressor (for example, the discharge tube) and are not pinched by the refrigerator body when installing the unit in place. Secure the wiring harness with plastic clamps, if provided by the design.
Typical installation errors and their consequences
One of the most common mistakes is ignoring the orientation of the relay. As mentioned earlier, many induction relays only work in a certain position. If you install such a relay upside down, gravity will not allow the core to move correctly, and the starting winding will not turn off after starting, which will lead to an overload.
Another common mistake is poor contact. If the wire is not inserted all the way or the terminal is oxidized, heat will begin to be generated at the connection. This leads to melting of the relay plastic and destruction of the wire insulation. In the worst case, sparking occurs, which can cause a fire inside the technical compartment.
| Error | Symptom | Consequence |
|---|---|---|
| Windings (R and S) are mixed up | The compressor hums, does not start, the automatic switch knocks out | The starting winding or relay is burned out |
| Grounding is not connected | The refrigerator is working normally | Risk of electric shock during breakdown insulation |
| Relay inverted (for induction) | No start-up or constant operation of the starter | Overheating and failure of the compressor |
| Weak contact of wires | Sparking, crackling, burning smell | Melting of the terminal block |
Installing a relay with inappropriate current parameters is also considered an error. If the protection threshold is too high, the relay will not turn off the engine when jammed, and it will burn out. If it is too low, the refrigerator will constantly turn off without having time to reach the temperature.
Checking performance after installation
After installation is completed and all connections are visually checked, you can begin testing. Plug in the refrigerator. In the first seconds, you can hear the characteristic click of the relay, followed by the smooth hum of the operating compressor. This is a sign of a successful launch. If a click is heard, but the motor does not start, and after a few seconds a second click is heard (protection is turned off), then the problem is not solved.
If the start fails, immediately disconnect the device from the network. Re-checking the circuit, the quality of the contacts and the condition of the compressor itself is mandatory. Perhaps the cause of the malfunction lies deeper - in the interturn short circuit of the motor windings or mechanical jamming of the piston group.
Pay attention to the heating of the relay housing during the process work. It may become slightly warm during the first 15-20 minutes of operation, but should not be so hot that it is impossible to touch. Excessive heating indicates high contact resistance or a malfunction of the relay itself.
⚠️ Attention: Compressor specifications and circuit designs may vary depending on the specific model and year of manufacture. Always check the manufacturer's official documentation or the markings on the unit nameplate before starting work.
Frequently asked questions (FAQ)
Is it possible to replace a three-pin relay with a four-pin one?
In most cases, this is not possible without changing the wiring design. Four-contact relays often have an additional function or a different phase-neutral separation scheme. An attempt to adapt may lead to incorrect operation of the protection. It is better to look for an exact analogue by catalog number.
Why does a new relay burn out immediately after installation?
This may indicate a malfunction of the compressor itself (turn-to-turn short circuit), which is why the starting currents exceed the norm by several times. The cause may also be an incorrect connection diagram or unstable voltage in the network. Diagnostics of the motor-compressor is required.
Do I need to solder the wires when replacing the relay?
Usually modern refrigerators use detachable connections (chips). Soldering is rarely required, only if the wires are broken near the terminal or rotted. In this case, you need to strip the wire, put on a new terminal and crimp it, or carefully solder it, observing the insulation.
How to determine that it is the relay that has burned out, and not the compressor?
If when you turn on you hear a click, then a buzz, and after 5-10 seconds another click and silence - most likely the problem is in the relay or starting winding. If the compressor hums, but does not start, and at the same time the motor housing gets very hot, there is a high probability of the compressor jamming or breakdown of the windings on the housing.