Sudden stoppage of the refrigerator is a situation faced by many owners of household appliances. If you notice that the compressor hums but does not start, or it turns on only for a few seconds and immediately turns off, then in 80% of cases the problem lies in the starting device. It is this small component that is responsible for starting the engine and protecting its windings from overloads.
The compressor relay is a key element of the electrical circuit that supplies an impulse to the starting winding of the motor. Its malfunction can lead to serious consequences, including burning of the motor windings or jamming of the piston group. Therefore, timely diagnostics and correct replacement of the part can extend the life of your refrigerator for many years.
In this article we will look in detail at how it works starting relay, what types of these devices there are and how to perform the replacement yourself without calling a technician. You will learn how to identify signs of breakdown and what to look for when buying a new spare part.
The operating principle and types of starting relays
To understand how to properly connect a part, you need to understand the physics of the process. When starting, the electric motor requires significantly more energy than to maintain operation. Starting relay temporarily connects an additional starting winding, creating the necessary torque. As soon as the engine picks up speed, the relay opens the starting winding circuit.
The most common are electromagnetic devices. In them, current passes through a coil, creating a magnetic field that lifts the core and closes the contacts. When the rotor speed reaches 75-80% of the rated speed, the current drops and the core drops under the influence of gravity, opening the circuit. There are also induction and electronic (solid-state) relays that work on a different principle, but perform the same function.
It is important to understand that the relay is often combined with thermal release. This bimetallic plate, which bends when heated from increased current and forcibly breaks the circuit, preventing the compressor from overheating. That is why replacement is often carried out in a complex manner, complete with a thermal relay.
Diagnostics of faults before replacement
Before disassembling the refrigerator, you need to make sure that the problem is in the relay. There are several characteristic symptoms that indicate a failure of the starting device. If the refrigerator makes a characteristic click, followed by a hum, and then another click and silence, this is a sure sign that the trigger mechanism does not work.
Often the cause is mechanical destruction of internal components. Electromagnetic relays have a movable core and a coil inside. Over time, vibration or power surges can cause the coil to burn out, and the contacts to burn or stick. A visual inspection often helps to identify the problem: if soot is visible inside the housing or a burning smell is felt, the part requires replacement.
You can also check the relay with a multimeter. To do this, you need to call your contacts. In the normal state, the resistance should be close to zero (for closed contacts) or infinity (for open contacts). If the device shows an open where there should be a circuit, or a short circuit, the part is faulty. It is also worth checking thermal relaywhich should be closed in the cold state.
Why does the relay burn out?
A common cause of failure is low voltage in the network. When the voltage drops, the current in the motor windings increases, which leads to overheating and tripping of the protection. If the voltage in your network often fluctuates, it is recommended to install a stabilizer.
Tools and preparation for work
Successfully replacing the compressor relay does not require complex professional equipment. However, safety must come first. Before starting any work, you must completely turn off the power to the refrigerator by removing the plug from the socket. Working with live electrical appliances is strictly prohibited.
You will need the following tools and materials:
- 🛠️ A set of screwdrivers (Phillips and flat) for removing the back panel and clamps.
- 🔧 Pliers or wire cutters for working with wires and clamps.
- 🧤 Dielectric gloves for protection against accidental electric shock.
- 📷 Smartphone or camera to photograph the connection diagram before disassembly.
Pay special attention to the selection of a new part. Relays are selected strictly according to the compressor model or technical characteristics (engine power, type of refrigerant). There are no universal solutions: a relay from Atlanta may not fit Indesit due to differences in the housing design and current characteristics.
☑️ Preparation for replacing the relay
Step-by-step instructions for replacing the relay
The replacement process begins with removing the rear protective panel of the refrigerator. It is usually secured with screws or snaps. After removal, you will see the compressor - a black “barrel” at the bottom of the unit. A box fits its terminals, which is the desired relay.
Carefully remove the fixing clamp or bracket that holds the relay to the compressor terminals. Be careful: the wires can be stiff, and sudden movement can damage the insulation or break off the terminals. Remove the old relay and compare it with the new one. Pay attention to the markings, the number of contacts and their location.
Now the most important thing is the connection. Use the photo you took earlier as a guide. Place the new relay onto the compressor terminals. It should fit tightly, without backlash. If the connectors are different, it may be necessary to re-solder the wires, but in most cases simply installing the part in place is sufficient. Make sure the relay is installed in the correct position: the body usually has a marking UP or an arrow pointing up.
After installation, secure the relay clamp and return the back panel to its place. Plug in the refrigerator. If you hear the compressor start confidently and after some time cold appears in the freezer, it means the replacement was successful.
⚠️ Attention: If after replacing the relay the compressor hums but does not start, immediately turn off the appliance. Long-term operation in this mode ("buzz" mode) can burn out the motor windings in a matter of minutes.
Connection diagram and color marking
Understanding the connection diagram is necessary in case the old relay has burned out completely and the markings on it are not readable. Refrigerator compressors usually have three terminals forming a triangle. They are designated by letters or the color of the insulation.
The standard marking is as follows:
- 🔵 Start winding —often indicated by the letter S or the color blue/black.
- 🟢 Working winding (Run) —denoted by the letter R or color green/white.
- ⚫ Common wire (Common) —indicated by the letter C or the color red/yellow.
The relay is placed directly on these contacts. The starting relay connects the starting and working windings at the moment of start, and the thermal relay is connected to the break in the common wire. An error in the connection can lead to a short circuit or the motor operating on only one winding, which will cause it to quickly overheat.
Below is a table of contact correspondence for the most popular types of compressors:
| Compressor type | Starting winding | Working winding | General contact |
|---|---|---|---|
| Atlas (CKN, CTK) | Upper left | Upper right | Bottom |
| LG (MA series) | Left | Right | Bottom |
| Danfoss (NL, NF) | Top | Right | Left |
| Embraco | Depends on the model | Depends on the model | Depends on the model |
⚠️ Attention: The location of the contacts may vary depending on the year of manufacture and the specific modification of the compressor. Always check the technical documentation or markings on the motor housing itself.
Frequent errors when connecting
Even experienced professionals sometimes make mistakes, let alone beginners. The most common one is ignoring the relay orientation. As already mentioned, electromagnetic devices are sensitive to position in space. If you install the relay sideways or upside down, the core will not be able to return to its original position, and the starting winding will remain on, which will lead to its combustion.
Another mistake is using a relay that is not suitable for the current. If you install a relay from a low-power compressor on a powerful unit, the contacts will constantly spark and quickly fail. Conversely, a relay with a large current reserve may simply not break the circuit in time.
They also often forget to check the condition of the wires. If the insulation on the wires going to the relay is melted or cracked, it must be repaired using heat shrink or electrical tape. Poor contact at the junction of the wire and the relay terminal causes heat and can cause a fire.
Can a universal relay be used?
There are universal starting relays with three contacts that fit many models. They are often more reliable than the original ones, but require correct wiring according to the attached diagram.
Safety and prevention
Refrigerator repair is associated with the risk of electric shock and mechanical injury. Always work in good light and use proper tools. If you feel unsure of your abilities, it is better to turn to professionals.
To prevent repeated breakdowns, it is recommended:
- 🧹 Regularly clean the capacitor (grid at the back) of dust and animal hair.
- 🔌 Use a surge protector or voltage stabilizer.
- ❄️ Do not place the refrigerator close to the wall to ensure ventilation.
- 🔊 Pay attention to any changes in the sound of the compressor.
Following these simple rules will help avoid overheating of the compressor and will extend the life of the start relay. Remember that the relay is a consumable item, but its frequent replacement indicates deeper problems in the system.
⚠️ Attention: Design details and electrical diagrams may vary slightly depending on the manufacturer and model year. Before starting work, check the official instructions for your refrigerator.
Questions and answers (FAQ)
Is it possible to start a refrigerator without a relay?
Theoretically, you can start a compressor without a starting relay by applying a pulse to the starting winding manually, but this is extremely dangerous and requires special skills. The refrigerator will not be able to operate for a long time without a relay - the starting winding will burn out. Operation without a thermal relay is also prohibited, since the engine will burn out at the first overload.
Why does the new relay click, but the refrigerator does not freeze?
This may indicate several problems: the compressor itself is faulty (an interturn short circuit or wedge), a freon leak, or a blockage in the system. It is also possible that the new relay is defective or does not meet the specifications. It is necessary to carry out a full diagnosis.
Where can I find the relay markings for purchase?
The markings are usually applied to the body of the relay itself (for example, R6, PZR, RT). If the inscription is erased, look for the compressor model number (on the sticker next to the terminals) and select a relay from compatibility catalogs for this series of motors.
How long does the starting relay last?
The service life of the relay depends on the quality of electricity and the frequency of switching on of the refrigerator. On average, a part lasts 5-10 years. Frequent power surges and overheating of the compressor significantly reduce this period.
Is it dangerous to change the relay yourself?
If you follow safety precautions (disconnect the device) and act carefully, the risk is minimal. The main danger is electric shock when the device is plugged in or damage to the compressor tubes due to careless handling of the tool.