A sudden stop of the compressor or, conversely, its continuous operation without cooling is always stressful for the owner of household appliances. Often the cause of this situation is a small part called a start-up relay. It is this element that is responsible for starting the engine and protecting it from overloads, so its malfunction instantly disrupts the operating cycle of the entire unit. You can understand that the problem lies in the relay by the characteristic sounds and behavior of the motor if you listen carefully to the operation of the device.
Diagnostics of this part does not always require deep technical knowledge, since the external manifestations of a breakdown are often obvious even to an inexperienced user. Start relay is a kind of switch that supplies current to the motor windings at the time of start. If it fails, the compressor either does not start at all, or tries to start, but immediately stalls. In this article we will analyze in detail all the symptoms, testing methods and nuances that will help you accurately determine the condition of this important unit.
It is worth noting that ignoring the first signs of a malfunction can lead to more serious consequences, including combustion of the compressor itself. Modern inverter models may behave differently than classic ones linear units, but the basic diagnostic principles remain similar. Before calling a technician or buying a new part, it is necessary to conduct a visual inspection and simple tests, which can often save a significant amount of money on repairs.
Main symptoms of a faulty start-up relay
The first and most striking sign that starting relay out of order, there is a characteristic click that repeats at certain intervals. You may hear the compressor trying to start, there is a loud click, the motor hums for a few seconds, and then there is another click and then there is silence. This cycle can be repeated endlessly until you unplug the device, which indicates that the starting mechanism cannot keep the contacts closed to start the engine.
Another important symptom is the complete failure of the compressor to turn on when the lighting inside the chamber is on. If the light is on, it means that voltage is supplied to the network, but it does not reach the engine due to an open circuit in the relay. In some cases, you may notice that the relay body or adjacent part of the compressor becomes very hot, which indicates a short circuit inside the coil or sticking contacts. Thermal protection in this case, it may work constantly, preventing the motor from even trying to work.
- 🔊 The compressor is humming 5-10 seconds, then a click is heard and it goes silent.
- 🔌 The refrigerator is plugged in, there is light, but the motor is completely silent.
- 🔥 The relay or the back of the compressor has an increased housing temperature.
- 👃 The appearance of a burning or melted smell plastics in the engine compartment area.
⚠️ Attention: If you smell burning or see sparking, immediately unplug the refrigerator from the power supply. Continuing operation in this condition can lead to a wiring fire or complete failure of an expensive compressor.
It is important to distinguish between the symptoms of a relay failure and other malfunctions, for example, jamming of the compressor piston group. In the case of a relay, the motor often makes sounds of operation, but does not start, whereas with a mechanical jamming, the hum may be more strained or absent altogether. Electronic modules controls In new models, starting can be blocked when a short circuit is detected in the relay circuit, so the lack of response to switching on can also be a protective reaction of the system.
Visual inspection and initial diagnostics without tools
Before resorting to using a multimeter or other measuring instruments, it is necessary to conduct a thorough visual inspection of the part. To do this, you need to unplug the refrigerator, move it away from the wall and gain access to the compressor, which is usually located in the lower rear part of the case. Having removed the protective cover, you will see a compressor to which a small plastic or metal box is attached to the side or bottom - this is the desired starting relay.
Carefully remove the relay from the compressor contacts, having previously photographed or memorized the wiring diagram. Inspect the body of the part for cracks, signs of melting or blackening. If traces of burning are visible inside the case, and the contacts look burnt, then the diagnosis is complete - the part requires replacement. Also pay attention to the condition of the wires: if the insulation melted, perhaps the problem was an overload, which also affected the relay itself.
☑️ Initial inspection of the relay
There is a simple but effective folk test method, which is often called the “rattle test”. Shake the removed relay near your ear. If a distinct ringing or knocking sound is heard inside, as if some part had fallen off, this is a sure sign of destruction of the internal structure. In good condition, no elements should be loose inside, since there are coils and contacts fixed in a monolithic housing or tightly pressed by a spring.
- 👀 The presence of black carbon deposits on the contact pads inside the relay.
- 💥 Visible cracks on the plastic body of the part.
- 👂 The sound of a dangling object when shaking the relay near the ear.
- 🌡️ Traces of thermal effects on the wires approaching the relay.
However, a visual inspection does not always give a 100% guarantee. The contacts may appear clean and the coil intact, but electrical resistance may be compromised. Therefore, if no external defects are found, but the symptoms persist, it is necessary to proceed to an instrumental check using multimeter. This will allow you to identify hidden breaks or short circuits that are not visible to the eye.
Checking a relay with a multimeter: step-by-step instructions
For accurate diagnostics, you will need a multimeter - a device capable of measuring the resistance of an electrical circuit. Before starting measurements, make sure that the relay is completely disconnected from the compressor and wires. Switch the multimeter to resistance measurement mode (Ohms) and touch the probes to the contacts that should close the trigger circuit. Depending on the type of relay (inductive or posistronic), the readings may vary, but the principle remains the same.
If you are checking an induction relay, then in normal condition the coil resistance should be close to zero or a few ohms. An infinitely high resistance (one on the DMM screen) will indicate an open circuit. PTC relays are characterized by the presence of a posistor, the resistance of which changes when heated, so they need to be checked quickly, before the element heats up from the measuring current or hands.
| Test type | Good condition | Faulty condition | Probable reason |
|---|---|---|---|
| Coil continuity | Resistance 0-50 Ohm | Infinity (break) | Winding burned out |
| Start contacts | Closed when pressed | Does not close | Mechanical jamming |
| Thermal protection | Circuit closed (cold) | Circuit broken | Protection spiral burned out |
| Posistor | Low resistance (cold) | High resistance | Crystal degradation |
Special attention should be paid to thermal protection, which is often built into the relay housing or mounted nearby. It should “ring” briefly when cold. If the multimeter shows an open circuit on the cold thermal protection, then it has burned out and requires replacement along with the relay. Electrical circuit in this case it will not be closed and the compressor will not receive power.
Nuances of checking posistor relays
Posistor relays do not have moving mechanical parts. They use a ceramic element that sharply increases resistance when heated by current, opening the starting winding. When checked with a multimeter, a cold posistor should show low resistance (3-50 Ohms). If it shows infinity right away, it is faulty. The main feature: after checking, the posistor must be cooled for 3-5 minutes before taking another measurement, otherwise it will remain in an open state.
Differences between induction and posistor relays
Understanding the type of relay installed in your refrigerator is critical for correct diagnosis and selection of a replacement. Inductive relays - these are older models, the operation of which is based on an electromagnetic coil and a moving core. When current is applied, the core retracts and closes the contacts of the starting winding. Such devices are position sensitive: they only work in a certain position relative to the ground, which is important to consider when installing the refrigerator.
Posistor relays (or PTC relays) are more modern and do not have moving mechanical parts. They are based on a semiconductor element - a posistor, which changes its resistance depending on temperature. When turned on, it is cold and passes current, starting the engine, then heats up and opens the circuit. They are less noisy, tolerate vibration more reliably, but are afraid of power surges and can fail when switched on frequently.
- 🔩 Induction: have a movable core, make clicks, depend on the orientation in space.
- 🔌 PTC: have no moving parts, operate silently, do not depend on tilt.
- ⚡ Induction: contacts can burn due to sparking when opened.
- 🌡️ PTC: require time to cool down (3-5 minutes) before restarting.
When replacing a part, it is extremely important to select an analogue with identical characteristics. Even if the relay fits in the seat, its electrical parameters (operation current, delay time) must meet the requirements of a particular compressor. Installing the wrong relay may result in the engine not starting or the starting winding burning out.
⚠️ Attention: Do not attempt to repair sealed posistor relays by disassembling them. Their housing is often filled with compound or soldered, and a violation of the integrity will lead to loss of thermal contact and rapid failure after switching on.
Why the starting relay fails: the main reasons
Resource of the starting relay is not infinite, and sooner or later it will require replacement. One of the main reasons for failure is the natural wear of contacts. Each start of the compressor is accompanied by micro-sparking at the moment of closing or opening the circuit, which leads to the formation of carbon deposits and an increase in resistance. Over time, the contacts burn so much that they no longer conduct the current required to start the engine.
Unstable voltage in the electrical network also plays a destructive role. Voltage surges can cause overheating of the inductor or breakdown of the posistor. If the lights flicker frequently in your home or voltage surges occur, the relay will wear out much faster. Current overloadswhich occurs when the piston group of the compressor moves tightly, forces the relay to work in extreme mode, which also shortens its service life.
The influence of external factors such as high humidity or temperature in the room also cannot be discounted. Moisture can oxidize the contacts inside the case, especially if the seal of the plastic casing is broken. In addition, frequent turning off and turning on of the refrigerator (for example, when moving or defrosting) does not allow the posistor to cool down, which leads to its operation in abnormal mode and eventual failure.
Replacing the relay: can you do it yourself
Replacing the starting relay is one of the simplest operations in repairing refrigerators, accessible even to a beginner. If you are convinced that the problem is in this particular part, it is enough to purchase a new analogue with the same model number or electrical parameters. The installation process takes no more than 15-20 minutes and does not require any special tools, except perhaps a screwdriver for removing the protective cover.
When installing a new relay, it is important to observe the connection polarity, if it is indicated on the diagram, and correctly orient the part relative to the compressor (especially for induction models, where there is a “UP” mark or an upward arrow). Incorrect installation can lead to the mechanism simply not working or working incorrectly. Make sure that the contacts are tightly placed on the pins of the compressor and are not loose.
However, if after replacing the relay the situation has not changed (the compressor hums, but does not start), the problem may be deeper. Perhaps the compressor itself is faulty (interturn short circuit or wedge) or the wiring is broken. In such cases, self-repair can be dangerous and ineffective, so it is better to contact a professional technician for an in-depth diagnosis.
Frequently asked questions (FAQ)
Is it possible to temporarily start the refrigerator without a relay?
Technically, you can start the compressor directly, by closing the contacts of the starting winding manually, but doing this is strictly not recommended without experience. This is life-threatening (risk of electric shock 220V) and can finish off the compressor, since the starting winding is not designed for long-term operation and will burn out in a few seconds without turning off the relay.
How much does a new starting relay cost and where to buy it?
The cost of the relay varies from 500 to 2000 rubles depending on the model and manufacturer. You can buy it in spare parts stores for household appliances, at radio markets, or order online using the catalog number indicated on the body of the old part.
Why does a new relay burn out a few days after installation?
Frequent combustion of new relays indicates a problem not in the part itself, but in the system. Most likely, the compressor is faulty (taking too much starting current) or there are problems with the wiring. Also, the reason may be the incorrect selection of the type of relay (for example, they installed a relay on a powerful motor for a weak one).
Does the tilt of the refrigerator during transportation affect the operation of the relay?
The tilt itself does not break the relay, but if the refrigerator is induction, it may not start if it is not level. For posistor relays, the slope is not critical. However, if the refrigerator was shaken strongly during transportation, an internal part could move away from the contacts, which would lead to breakdown.