Failure of a refrigerator is always stressful, especially when there are perishable products left in the chamber. Often the cause of a breakdown is the failure of the starting relay, which is responsible for starting the compressor engine. Understanding how to connect a refrigerator compressor relaycan save your budget and time, allowing you to carry out repairs yourself without calling a technician.
This component is a small plastic or ceramic case that is attached directly to the compressor. Inside it there is a mechanism that closes the starting winding of the engine for a split second, allowing the rotor to gain speed. Without a working relay, the compressor will either not start at all, or will emit a characteristic click and hum, going into thermal protection.
In this article we will analyze in detail the process of diagnostics, dismantling the old device and installing a new one. You will learn how to correctly determine the polarity of the windings, avoid common mistakes and safely work with live electrical appliances.
Principle of operation and types of starting devices
Before you begin replacement, you need to figure out what exactly you are repairing. The start relay is an electromagnetic or thermal switch. When the refrigerator is turned on, current passes through the coil, creating a magnetic field that draws in the core and closes the contacts of the starting winding. As soon as the motor reaches the desired speed, the current drops and the contacts open. There are different types of these devices, and compressor relay connection diagram may vary slightly depending on the design.
The most common are inductive (electromagnetic) relays, where the closure occurs due to the current in the starting winding. There are also posistor relays in which the role of a switch is performed by a ceramic element that changes its resistance when heated. Old models are characterized by thermal relays operating on the basis of a bimetallic plate.
- 🔌 Induction: they work due to electromagnetic induction, typical for Soviet and old imported refrigerators.
- 🔥 Posistor: use heating of the crystal, are more reliable and silent, installed in modern technology.
- ⚙️ Combined: combine the functions of a starting and thermal protective relay in one housing.
⚠️ Attention: Never try to start the compressor bypassing the relay, applying voltage directly to the windings without the appropriate skills. This is guaranteed to lead to engine combustion or electric shock.
Why do relays burn out?
The main reason for failure is a voltage surge in the network or natural wear of the contacts. Also, frequent switching on and off of the refrigerator (for example, due to a loosely closed door) reduces the life of the device, since the contacts do not have time to cool down and burn.
Diagnostics of a malfunction before replacement
Replacement of the refrigerator compressor relay is not always required. Sometimes the problem lies in oxidation of contacts or failure of fastening. The first sign of a malfunction is a characteristic sound: the refrigerator hums for 3-5 seconds, then a loud click is heard and the motor stops. After some time, the cycle repeats. This indicates that starting relay cannot keep the contacts closed or does not open them in time.
For accurate diagnostics, it is necessary to remove the device from the compressor. Before doing this, be sure to unplug the refrigerator from the power supply! Carefully remove the rear protective panel to gain access to the motor. The relay is usually placed on three pins of the compressor and secured with a bracket or clamps. Inspect the case for melting, cracks or traces of burning.
If visual defects are not visible, you can try to “ring” the device with a multimeter. In normal condition, the contacts should ring in a certain position. However, the most reliable way to check is to replace it with a known-good analogue. If after installing the new relay the refrigerator started working, then the problem was in this unit.
Preparation for replacement and selection of a new relay
A critically important step is the correct selection of spare parts. Compressor relay selected strictly according to the engine model or the marking of the old device. There are practically no universal solutions, since the current characteristics and contact locations of different manufacturers (Danfoss, Secop, Atlant, Indesit) may differ.
Remove the old relay and carefully study the markings on its body. It usually lists the part number or compatible series of compressors. If the markings are erased, look for information on the model of the refrigerator or engine itself. Pay attention to the number of pins: there may be three, but sometimes only two are used, and the third is used for grounding or thermal protection.
- 📋 Marking: write down all the numbers and letters from the body of the old device before purchasing.
- 📐 Geometry: make sure that the shape of the new relay matches the seat on compressor.
- ⚡ Current: Check that the rated current (indicated in Amperes) matches the characteristics of your motor.
⚠️ Attention: The characteristics of compressors and relay compatibility may vary depending on the production batch. Always check the connection diagram on the new device with the diagram on the old one or in the manufacturer’s technical documentation.
Step-by-step connection instructions
The process of installing a new element requires care and adherence to the sequence of actions. The main rule is that all work is carried out only with the refrigerator completely disconnected from the network. Do not touch live wires.
First you need to determine which pin on the compressor is responsible for what. They are usually arranged in a triangle. The vertical row is the windings, and the side pin is the common one. To avoid mistakes, use a multimeter in dial mode. The resistance between the common point and the starting winding will be higher than between the common and working windings. Correct definition starting and operating windings is the key to a successful launch.
☑️ Algorithm for replacing the relay
Now you can begin installation. Place the new relay onto the compressor pins. It should fit tightly, but without excessive force. If the device has additional wires (for example, for thermal protection), connect them according to the color coding or diagram, which is often printed directly on the relay or compressor housing.
Contact diagram (standard):Upper contact: Start winding
Bottom contact: Working winding (Run)
Side contact: Common
After installing the mechanical part, secure the relay with a fixing strip or clamps. Make sure the wires are not pinched or touching hot parts of the compressor. Only after visually checking the correct assembly can you turn on the refrigerator.
Correspondence table and common errors
When performing work, beginners often make mistakes that can lead to repeated breakdowns. To systematize knowledge, consider the main problems and ways to solve them in the table below.
| Problem | Possible cause | Solution |
|---|---|---|
| The compressor hums, but does not start | Stuck piston group or the relay is burned out | Check the relay, if it is working, try to start it via ROM |
| Click and silence | Faulty starting device | Replace the relay with a new one |
| The motor heats up and turns off | Thermal protection or relay is faulty | Check the winding resistance and protection |
| Sparking inside the relay | Burnt contacts | Urgent replacement of the relay |
One of the common mistakes is ignoring the condition of the motor windings themselves. If compressor has an interturn short circuit, installing a new relay will only give a short-term effect, after which the new part will burn out. Therefore, before replacing, always measure the resistance of the windings.
It is also important to correctly orient the relay in space. Some models (especially older induction models) are sensitive to position relative to the horizon. If you turn such a relay upside down, it may not work or may stick. Always install the part in the same position in which the original one was.
Checking performance after installation
Once you have figured it out, how to connect the starting relay, and put everything back together, the testing stage begins. Plug in the refrigerator. In the first seconds you should hear a smooth hum of the engine. If a loud click is heard and the motor stops, immediately turn off the device - it means that the assembly was performed incorrectly or the part is defective.
Pay attention to the temperature of the relay body during operation. After 10-15 minutes of operation, it may warm up slightly, but should not be hot. If the plastic begins to melt or smell burnt, this indicates poor contact or a mismatch in the current characteristics.
Make sure that the temperature in the refrigerator compartment begins to drop. If the motor is running, but there is no cold, the problem may not be an electrical problem, but a freon leak or a clogged capillary tube. In this case, the relay repair was carried out correctly, but a more complex technical intervention is required.
Is it possible to use a relay from another refrigerator?
You can use a relay from another model only if their electrical characteristics (current, voltage) and contact diagram are completely the same. Visual similarity does not guarantee compatibility. It is best to select the part by catalog number.
Why did the new relay burn out after a week?
This may indicate problems with the compressor itself (interturn short circuit, jamming), voltage surges in the network or incorrect installation (poor contact, inverted position). It is also possible that a relay has been selected with a lower rated current than required.
Do I need to solder the contacts when replacing?
In 95% of cases, soldering is not required. Modern relays are placed on the compressor bayonets (“male-female”) and fixed mechanically. Soldering is only needed if you are changing the connector on the wire, but this requires skill and care so as not to damage the insulation.
Is it dangerous to change the relay yourself?
The main risk is electric shock when the device is turned on. If you follow safety precautions (work only with the refrigerator unplugged) and do not have heart problems or epilepsy (due to possible sparking), the process is quite safe for the home handyman.