Failure of the engine starting system is one of the most common reasons why a household refrigerator stops cooling. Equipment owners often notice that the compressor hums for a couple of seconds, clicks and turns off, or is completely silent. In most cases, the culprit is start-up relay, which requires replacement or thorough diagnosis. Independent intervention in the electrical part of the unit is possible, but requires strict adherence to safety precautions and an understanding of the operating principle of the device.
Before proceeding with disassembly, it is necessary to turn off the power to the device and move it away from the wall to provide access to the back wall. It is there, in the lower part, that the motor-compressor is located, on the shank of which the required part is fixed. Incorrect removal can lead to damage to the copper tubes or the relay itself, so it is important to act consistently and carefully.
In this article we will look in detail at how to remove the casing, disconnect the contacts and carry out an initial check of the element. You will learn how induction starters differ from posistor starters, and you will understand whether it is worth trying to repair the part or whether it is easier to buy a new one. Correct diagnostics will save you time and money, allowing you to avoid calling a technician for a basic operation.
Preparation of the workplace and safety
Any work with electrical appliances begins with a complete disconnection from the network. Unplug the cord from the outlet and check that the plug is not damaged. If the refrigerator has just been running, let it stand for 10-15 minutes so that the refrigerant in the system has time to redistribute and the pressure equalizes. This will reduce the load on the compressor during subsequent startup attempts after repair.
You will need to move the unit away from the wall so that you have clear access to the rear panel. It is best to carry out work in good lighting, as the wires and terminals at the bottom of the refrigerator are often covered with a layer of dust or have a dark color. Prepare a clean surface on which to place the removed parts to avoid losing small screws or fasteners.
⚠️ Warning: Never attempt to open or repair a live relay. Even briefly touching live parts while the device is plugged in can result in a severe electric shock.
For work you will need basic tools: flat-head and Phillips screwdrivers, pliers with insulated handles and, preferably, a multimeter to test the circuit. If you do not have a tester, a visual inspection can only give a rough idea of the condition of the part, but does not guarantee an accurate diagnosis. Also prepare a dry rag to clean the contacts from oxides and dirt.
Removing the protective box and accessing the compressor
You can only get to the relay through the back wall of the refrigerator. In modern models, such as Indesit or Atlant, the compressor is often closed with a metal or plastic casing. It is secured with latches or screws. If the casing is metal, carefully unscrew the fasteners. Plastic covers are usually held on by clips, which must be carefully squeezed out so as not to break the plastic, which has become brittle over time.
After removing the casing, you will see a black barrel-shaped unit - this is the compressor itself. The relay is placed directly on three contact pins protruding from its body. There may be a lot of dust around, so before starting to manipulate the wires, it is better to wipe the area around the motor with a dry cloth. This will prevent debris from getting inside the electrical connections.
The first step is to remove the retaining bracket or strip that holds the relay to the compressor housing. It can be metal or plastic. If the strip is metal and rusted, do not use excessive force to avoid breaking the mounting tab. It’s better to drop a little penetrating lubricant and wait a couple of minutes.
☑️ Check before removal
It is important to remember or photograph the position of all wires before disconnecting them. Although it is difficult to mix up the contacts due to the different shapes of the connectors, visual fixation will help to avoid errors during assembly. Some models have additional grounding wires, which also need to be carefully disconnected.
Removing the relay from the compressor contact group
The most crucial moment is removing the relay from the compressor starting pins. The part can fit very tightly, especially if the refrigerator has been used for a long time and in conditions of high humidity. Do not try to loosen the relay by its plastic parts or wires - you risk tearing off the terminals or damaging the housing.
Most relays have a marking UP or an arrow indicating the top position. Remember this orientation, as new parts often require installation in a specific position for the gravity mechanism to work correctly (if we are talking about older types). Carefully take the relay by the body and begin to pull it towards you, slightly rocking it from side to side.
If the part does not give in, you can use a flat-head screwdriver to pry the base a little, but you need to act extremely carefully. The force must be directed strictly perpendicular to the mounting plane so as not to bend the compressor contact pins. Bent studs can lead to poor contact or even a short circuit in the future.
After the relay is removed, inspect the seat on the compressor. There should be no soot, traces of melting or oxidation. If the studs are blackened, they need to be sanded with fine sandpaper or a file until they have a metallic shine. This will ensure reliable electrical contact when installing a new element.
Types of starting relays and their design features
Understanding the type of your relay is critical for proper diagnosis and replacement. There are two main types of devices: electromagnetic (induction) and posistor. Electromagnetic relays are more often found in older models of refrigerators, for example ZIL or early ones Biryusha. They work due to the movement of the core in the coil and have movable contacts.
Posistor relays are modern solid-state devices that do not have moving parts. Inside them there is a ceramic element (posistor), which changes its resistance when heated. They are more reliable, make less noise and do not depend on the position of the refrigerator in space, which is important during transportation.
You can visually distinguish them by their weight and number of contacts. Electromagnetic relays are usually heavier, have a metal body and often have two or three contacts. The posistor ones are lighter, made in a plastic case, and inside, when you shake, you can hear the ringing of the ceramic element. Also, posistors often have a more complex shape with additional terminals for fans or sensors.
| Characteristics | Electromagnetic relay | Posistor relay |
|---|---|---|
| Operation principle | Movement of the core in the coil | Change in resistance when heated |
| Moving parts | Yes (contacts, core) | No (solid state) |
| Position sensitivity | High (vertical only) | Low (works in any position) |
| Working resource | Limited by contact wear | High, depends from power surges |
When purchasing a new part, be sure to compare the markings of the old one. Even if the connectors are the same, the current and voltage parameters may differ. Using an unsuitable relay can lead to overheating of the compressor windings and eventual failure.
Fault diagnosis and testing with a multimeter
After you have managed to open access to the insides of the relay (if the design allows) or simply remove it from the compressor, you can begin checking. Electromagnetic relays are often characterized by visible carbon deposits on the contacts. If you disassemble the case and see black spots or melted plastic, the part definitely requires replacement.
Checking with a multimeter is the most reliable way. Switch the device to continuity or resistance measurement mode. For a posistor relay, the resistance at room temperature should be in the range of 10-50 Ohms. If the device shows infinity (open circuit) or zero (short circuit), the element is faulty.
Electromagnetic relays are checked using the winding circuits. The resistance between the contacts should be small, and in a vertical position (in working position) the contacts should close. In a horizontal position, the circuit opens. If the contacts are “stuck” or do not close, the relay will not work.
⚠️ Attention: When checking the posistor, remember that after heating it goes into high resistance mode. To check it again, you need to let the part cool for 20-30 minutes.
Also inspect the wires going to the relay. It often happens that the device itself is intact, but the wiring has burned out or melted at the contact point. In this case, you need to strip the wires and restore the connection using heat shrink or high-quality electrical tape.
Installation of a new element and test run
Installation of a new relay is carried out in the reverse order of removal. Insert the part onto the compressor studs until it stops, observing the orientation (marking UP up). Make sure the relay is seated tightly and is not loose. If a retaining bracket is used, return it to its place and securely fasten it.
Connect all electrical connectors according to the photographs or diagram taken earlier. The wires should fit tightly, without play. Lay the wires so that they do not touch the hot parts of the compressor or the sharp edges of the metal casing, if any.
What to do if the new relay clicks, but the refrigerator does not start?
If after replacing the relay the compressor hums, clicks and does not start, the problem may be deeper. This may indicate an interturn short circuit in the motor windings, jamming of the piston group, or a malfunction of the capacitor. In this case, professional diagnostics with measurement of current consumption are required.
After assembly, plug in the refrigerator. In the first seconds, listen to the engine. It should start smoothly, without buzzing or clicking. After 10-15 minutes, check the heating of the relay and compressor - they may be warm, but not hot. If everything works properly, put the back panel in place.
Frequently asked questions (FAQ)
Is it possible to repair a burnt-out relay yourself?
Theoretically, an electromagnetic relay can be disassembled, the contacts can be cleaned with sandpaper and put back together. However, this is a temporary measure: the contacts will burn again in a few days or weeks. PTC relays cannot be repaired because they are monolithic. It is safer and more reliable to buy a new part.
Why did the new relay burn out immediately after installation?
Most often this indicates a malfunction of the compressor itself. If the motor is "pulling" too much current or has a jammed mechanism, it will burn out the starter in seconds. Also, the cause may be a power surge in the network or incorrect installation (wrong type of relay).
How often should the starting relay be changed?
The service life of a high-quality relay is 10-15 years. However, with unstable voltage in the power grid or frequent power outages, the resource may be reduced to 3-5 years. If the refrigerator begins to click frequently and does not turn on, this is the first sign of wear.
Does the position of the refrigerator affect the operation of the relay?
Yes, if you have an electromagnetic (gravitational) relay installed. It only works in a vertical position. After transporting the refrigerator lying down, you need to let it stand upright for at least 2-4 hours before turning it on, so that the oil flows into the compressor crankcase and the relay is in the operating position.