The situation when the refrigerator stops freezing, and the compressor either hums but does not start, or clicks and immediately goes silent, familiar to many owners of household appliances. Often the reason for this behavior is a failure starting relay, which is responsible for starting the compressor engine. This is a small but critical detail, without which normal operation of the refrigeration system is impossible. Replacing this element yourself can save a significant amount on calling a technician if you approach the matter wisely and follow all safety measures.
Before you begin dismantling the old one and installing a new relay, you need to understand the principle of its operation. The device serves to supply a short-term pulse to the starting winding of the motor to start the rotor, after which it turns it off, leaving only the main winding to work. If you notice that the motor is trying to start, making a humming noise, but stalls after a few seconds, or the thermal protection is triggered, the problem most likely lies in this unit. In some cases, the relay may stick, causing the compressor to operate continuously, which is also unacceptable.
It is important to immediately note that any work on electrical equipment should be carried out only when the device is completely disconnected from the network. Voltage 220 volts poses a real threat to life, so ignoring this rule is unacceptable. It is also worth preparing the necessary tools in advance: a screwdriver, pliers and, possibly, a multimeter for checking contacts. If you have doubts about your abilities or you see obvious traces of melted wiring, it is better to entrust the repair to professionals, however, for most standard models the replacement procedure is quite simple and straightforward.
Diagnostics of a faulty start relay
The first step before purchasing a new part is accurate diagnosis. Clicking and lack of cold do not always mean that the relay is broken; sometimes the problem may lie in the compressor itself or the thermostat. However, if traces of burning, cracks in the body, or a characteristic smell of melted plastic are visually visible on the part, then replacement is necessary in any case. Often the cause of failure is wear of the internal contacts or jamming of the moving core.
For a more accurate check, you can use a multimeter by switching it to the dialing mode. If, when shaking, the relay makes a rattling sound, as if a piece of metal is dangling inside, this is a sure sign of destruction of the core or contacts. In a normally operating device there should not be such a sound, since the internal elements must be fixed. It is also worth checking the resistance of the windings if you have access to the contacts, but most often external signs and the nature of the compressor’s operation provide sufficient information.
⚠️ Attention: If after replacing the relay the compressor continues to hum and does not start, the engine itself may be jammed. Attempts to turn on multiple times can lead to final burnout of the windings.
It is also worth paying attention to the condition of the wiring suitable for the contact group. If the wires have turned black or the insulation has become brittle, they need to be stripped or replaced, as poor contact causes heating and re-breakage of the new part. Oxidized contacts increase resistance, which disrupts the operation of the entire starting circuit. A visual inspection often reveals problems that are not visible by simply ringing.
Preparation of tools and selection of a new part
The success of the repair directly depends on the correctness of the selected spare part. Starting relays come in different types: induction (with a heavy core), posistor (with a thermal tablet) and combined. They are not always interchangeable, so when purchasing a new part you need to rely on the markings of the old device or the model of your refrigerator. For example, for equipment Indesit or Ariston one types are often used, and for LG or Samsung others.
As for tools, you will need a minimum set to carry out the work. The main tool will be a Phillips or flat-head screwdriver for removing the protective cover and fastening clamps. You can also use needle nose pliers to carefully remove the terminals without damaging the wires. If you plan to check the integrity of the circuit, an indispensable assistant will be multimeter.
- 🔧 Screwdrivers (phillips and flat) for disassembling the casing.
- 🔌 Pliers or pliers for working with terminals.
- 🔋 Multimeter for checking electrical circuits.
- 🧤 Dielectric gloves for additional safety.
When choosing a new part, pay attention to the number of contacts and their location. Some relays have three contacts, others have four or more, depending on the presence of additional protection or features of the control circuit. Posistor relays are considered more modern and reliable, since they have no moving mechanical parts that could wear out. However, replacing an induction relay with a posistor relay is not always possible and requires knowledge of the electrical circuit of a particular compressor.
The process of dismantling the old relay
You should start by completely disconnecting the refrigerator from the power supply. Unplug the cord and move the unit away from the wall to gain access to the rear where the compressor is located. Let the equipment stand for 10-15 minutes so that the residual voltage in the circuits dissipates and you do not accidentally receive an electric shock when touching the contacts. This is a basic safety rule that should not be ignored under any circumstances.
Locate the compressor - this is the black metal tank at the bottom of the back wall. A freon tube and an electrical cable are connected to it, which leads to a plastic box. This box is the starting relay. In some models, it is covered with an additional metal casing, which must be removed by unscrewing the screws or straightening the fixing brackets. You must act carefully so as not to damage the cooling system tubes.
Remove the plastic relay casing. It is usually held in place by latches or a single screw. After removing the cover, you will see the part itself, put on three pins of the compressor. Carefully, without sudden jerks, remove the relay from the pins. If it fits tightly, you can slightly rock it from side to side. Then disconnect the wires running from the relay to the common terminal block or directly to the network. Remember or write down which wire was connected where, as the color coding may not be obvious.
⚠️ Caution: Do not use excessive force when removing the relay from the compressor pins. A sharp jerk can damage the contacts on the motor itself or break the suitable wires, which will complicate repairs.
If the relay is combined and also includes a thermal protection relay, it can be mounted on a common frame. In this case, it may be necessary to remove the entire structure. Inspect the removed part for external damage. Often you can see soot or melted plastic inside, which confirms the need for replacement. It is better not to throw away the old part immediately, but to take it with you to the store as a sample, so that the seller can help you choose an exact analogue.
Connection diagram and installation of a new relay
Installation of a new device is carried out in the reverse order of dismantling. First make sure the new relay has the same contact configuration as the old one. If you are using a universal relay, carefully study the connection diagram supplied with it, since the location of the contacts may differ from the original. The most important point is the correct orientation of the part: on the case there is usually a marking UP or an arrow indicating the top position.
Connect the wires to the corresponding terminals of the new relay. If there are terminal clamps on the wires, make sure they crimp the terminals tightly. Weak contact will lead to sparking and heating, which will again damage the part. For reliability, you can slightly tighten the terminals with pliers, but without fanaticism, so as not to split the ceramic base or plastic case.
The table below will help you navigate the typical markings of contacts on the relay and compressor:
| Designation on the diagram | Contact function | Wire color (often) | Note |
|---|---|---|---|
| C (Common) | General contact | Black / Red | Power is supplied from the mains |
| R (Run) | Working winding | Green / White | Main engine operation |
| S (Start) | Starting winding | Blue / Yellow | Only for starting |
| GND | Grounding | Yellow-green | Connects to the case |
After connecting the wires, put the relay on the pins of the compressor. It should fit tightly and with little effort. Make sure that the device is positioned strictly vertically (if required by design), as incorrect positioning may interfere with the operation of mechanical parts or heat dissipation. Fasten the fixing brackets or screw the screws if the design provides for rigid fastening.
☑️ Check before turning on
Operation check and first start
After installing all the elements in place, but before closing the back panel of the refrigerator, it is necessary to perform a test run. Plug in the power cord and listen carefully. The compressor should start within a few seconds (after the relay clicks) and run smoothly, without humming or vibration. If you hear the characteristic sound of a running motor and cold appears, it means the replacement was successful..
Pay attention to the current consumed by the refrigerator, if you have the opportunity to measure it with clamps. It must not exceed the nominal values indicated on the compressor nameplate. If the current is normal and the motor is running, you can let the equipment run for 15-20 minutes in the open state to make sure that the newly installed parts do not overheat. You need to touch the relay with your hand at this moment carefully, checking the temperature.
What to do if the compressor hums, but does not start?
If after replacing the relay the situation has not changed and the compressor hums, but does not start, the problem may be a jammed compressor piston or broken windings. In rare cases, the new relay may also be defective. Try gently tapping the handle of a screwdriver on the compressor body (not on the tubes!) at the moment of startup - sometimes this helps to break a jammed piston. If this does not help, the compressor needs to be replaced or professional diagnostics are required.
If everything went well, secure the protective cover and the rear panel of the refrigerator. Make sure that the wires are not pinched or touching hot parts of the compressor or pipes. During the first few hours of operation, watch the cycle of turning on and off: the refrigerator should gain temperature and turn off, and not run continuously. Continuous operation may indicate that the relay does not turn off the starting winding or the thermostat is faulty.
Frequent errors during connection and operation
One of the most common mistakes is ignoring the orientation of the relay during installation. Many models require a strictly vertical position for the gravity mechanism or heat dissipation to work properly. Installation upside down or on its side may cause the contacts to not open in time and the starting winding will burn out. Always look for the marking UP or arrow on the body of the part.
Another error is poor contact in the terminals. If you simply put the terminals on, but did not check the tightness of the connection, over time the contact point will begin to heat up. This leads to oxidation, an increase in resistance and, ultimately, to repeated failure. Quality contact is the key to the durability of the repair. Also, do not use a relay that is not designed for the given compressor power, even if it is physically suitable in size.
- ❌ Installing the relay in the wrong position (upside down).
- ❌ Using uninsulated or damaged wires.
- ❌ Ignoring cleaning contacts before installation.
- ❌ Using a relay with an inappropriate operating current.
Also, at least 5-10 minutes must pass between starts so that the pressure in the system has time to equalize. If you have tried to start the engine several times in a row, let it cool and rest before trying again. This will extend the life of the entire refrigeration system.
⚠️ Attention: Technical characteristics of refrigerators and connection diagrams may vary depending on the manufacturer and year of manufacture. Always check the technical documentation of the specific model or the markings on the compressor nameplate before starting work.
Questions and answers (FAQ)
Is it possible to install a relay from another refrigerator model?
This is only possible if the electrical parameters (current, voltage) and design (location of contacts, type of fastening) match. However, it is better to look for an original spare part or a complete analogue recommended by the manufacturer, since differences in characteristics can lead to rapid breakdown of the compressor.
Why does a new relay burn out immediately after installation?
There may be several reasons: the compressor itself is faulty (interturn short circuit, jamming), problems with the wiring (short circuit), or the wrong relay type is selected. Also, the relay often burns due to power surges in the network, so it is recommended to connect the refrigerator through a stabilizer.
How to understand that the relay is inductive or posistor?
An inductive relay is heavier; inside it has a movable core that rattles when shaken. A posistor relay is lighter, has no moving parts and does not make sounds when shaking. Visually, a posistor often looks like a small cylinder inside the housing.
Is it necessary to change the thermal relay along with the starting one?
If the thermal relay (overheating protection) is visually intact and can be read with a multimeter, it is not necessary to change it. However, if it shows signs of overheating or there are doubts about its performance, it is better to replace the entire unit, since these parts are often sold assembled.