Has the refrigerator stopped freezing, and the compressor either hums but does not start, or clicks and immediately goes silent? In most cases, the culprit of such a “symphony” is a failed start-up protection device, which includes thermal relay. This small but critical element protects the motor from overheating and ensures the initial starting of the rotor. If it burns out, the equipment turns into a useless cabinet, and products begin to deteriorate.
Before calling a technician or buying a new unit, it is necessary to carry out an accurate diagnosis. Often the problem lies precisely in an open circuit or sticking contacts, which is easily detected using ordinary household equipment. Self-testing does not require in-depth knowledge of electrical engineering, but does require strict adherence to safety precautions and attention to detail. In this article we will look at how to correctly ring the device, what parameters to pay attention to and how to distinguish a burnt part from a working one. multimeter. Self-testing does not require in-depth knowledge of electrical engineering, but does require strict adherence to safety precautions and attention to detail. In this article, we will look at how to correctly ring a device, what parameters to pay attention to, and how to distinguish a burnt part from a working one.
It is worth understanding that starting relay and thermal protection are often combined into one housing, especially in older models of refrigerators Atlant or Indesit. However, the principle of their operation differs: the starting one is responsible for supplying voltage to the second winding of the motor at the moment of start, and the thermal one opens the circuit when the current load is exceeded. A malfunction of any of these components leads to the unit stopping, so the entire assembly must be diagnosed.
The principle of operation and the design of the protective mechanism
To successfully find a breakdown, you need to at least superficially understand how this unit works. Hidden inside the plastic case is a bimetallic plate that responds to temperature changes. When the current passing through the compressor windings exceeds the norm, the plate heats up, bends and opens the electrical circuit. This prevents the engine from burning out. After cooling, the contacts should close again, allowing the refrigerator to start working.
Modern models often use posistor relays, where the role of a switch is played by a ceramic element with a sharply increasing resistance when heated. Diagnostics of such devices has its own nuances, but the basic principle of checking for circuit integrity remains the same. If the posistor or bimetallic plate does not return to its original state, the compressor will not receive the necessary impulse to start.
It is important to note that the thermal release can trip not only due to internal defects, but also due to problems with the compressor itself. If the motor is “bitten” or there is an interturn short circuit in the windings, the current increases and the protection honestly does its job by turning off the power. Therefore, if you find a fault in the relay, do not rush to rejoice - perhaps this is only a symptom of a more serious illness of the unit.
⚠️ Attention: Before any manipulations with the electrical components of the refrigerator, be sure to disconnect the device from the mains! Even after switching off, a charge may remain in the capacitors, which can cause an unpleasant electric shock. Let the equipment stand without power for 5–10 minutes.
Preparation for diagnostics and the necessary tools
To conduct a quality test, you will need a minimum set of tools that any home craftsman can find. The main device is multimeter (tester). It can be either pointer or digital, the main thing is that it correctly shows the resistance and can “squeak” when the circuit is tested. If you have an old analog device, make sure that the batteries in it are fresh, otherwise the readings will be incorrect.
In addition to the tester, prepare a flathead and Phillips screwdriver for removing the back panel of the refrigerator and dismantling the compressor casing. Pliers with thin jaws and fine-grained sandpaper may also be useful for cleaning contacts if oxide is visible on them. Don't forget about a flashlight, as the compressor area is often dark and cramped.
Before starting work, clear access to the back wall of the refrigerator. Move the unit away from the wall, remove the cardboard or metal cover covering the engine compartment. You need to get full access to the black barrel-shaped compressor, at the end of which the part you are looking for is attached. It is often closed with an additional plastic cap, which can be easily removed by hand.
☑️ Preparing to check the relay
Visual inspection and dismantling of the relay
The first step should always be a thorough visual inspection. Remove the relay from the compressor contacts. Usually it is simply put on three pins and secured with a bracket or clamp. Be careful: plastic becomes brittle over time and heat and can crack if moved carelessly. If the case has traces of soot, melting or a characteristic burning smell, further checking with a multimeter may no longer be necessary - the part definitely requires replacement.
Shake the relay near your ear. If something dangles and rattles inside, this is a bad sign. In a working device, all elements are rigidly fixed. Rattling may indicate destruction of the internal structure of the bimetallic strip or separation of the contacts. Also inspect the contact groups on the compressor itself: they should be clean, without black deposits and oxides.
If no visual defects are detected, we proceed to “digital” diagnostics. Switch the multimeter to resistance measurement mode (Ohms) or continuity mode (diode icon or sound wave). Connect the probes together to make sure that the device works and shows zero or makes a sound. Now you can start measuring the parameters of the relay itself.
Step-by-step instructions: how to ring with a multimeter
The testing process depends on the type of your relay, but the algorithm of actions is similar for most models. Pick up your device and find your contacts. Usually there are three or four. Two main contacts are responsible for thermal protection (normally closed), the others are for the starting circuit. In a cold state, the thermal protection contacts should ring short, that is, the resistance should be close to zero.
Attach the multimeter probes to the contacts of the thermal connector. If the device shows “1” (infinity) or is silent in dialing mode, the circuit is broken and the relay is faulty. If the resistance is several ohms or a squeak is heard, the circuit is intact. Now check the launch group. Here the resistance should also be minimal. Any deviation from zero or infinity indicates a problem.
For a deeper check, you can carefully open the relay housing (if it is not filled with compound). Inside you will see a bimetallic strip and contacts. Try pressing the plate lightly with your finger (be careful not to damage it). In a working relay, when pressed, a click should be heard and the contacts will open (the resistance will go to infinity). Once released they should close again. If there is no click or the contacts do not open, the mechanism is jammed.
| Test type | Normal reading | Symptom of malfunction | Action |
|---|---|---|---|
| Thermal circuit continuity | 0–2 Ohm (Sound) | Infinity (1) | Replacing the relay |
| Starting circuit continuity | 0–5 Ohm (Sound) | Infinity or >10 Ohm | Relay relay |
| Visual inspection | Clean contacts | Soot, melting, cracks | Replacement relay |
| Plate mechanics | Click when pressed | No reaction, sticking | Replacing the relay |
Checking the posistor deserves special attention if you have a modern device. A posistor in a cold state has a low resistance, but when voltage is applied it increases sharply. It is difficult to check its performance at home without supplying voltage, but if in a cold state it shows infinity or, conversely, zero (short circuit) - it is definitely dead. A critical sign of a faulty posistor is the absence of a characteristic click when trying to start the refrigerator.
Analyzing the results and searching for hidden problems
If the multimeter shows that the relay is working properly, but the refrigerator still does not work, the problem may lie deeper. The winding of the compressor itself may have burned out. To check this, you need to ring the contacts on the compressor connector (without a relay). There must be a certain resistance between them: between the starting and working windings, between the working and common windings, between the starting and common windings. If somewhere it shows infinity or a short circuit (0 Ohm), the engine is faulty.
It is also worth checking whether the compressor is “breaking through” to the housing. Place one multimeter probe on any contact of the engine connector, and the other on a copper tube or a cleaned area on the compressor housing. The device should be silent and show infinity. If there is resistance or a squeak, the motor has an insulation breakdown, operating such a refrigerator is life-threatening.
A frequent cause of false diagnosis is oxidation of the contacts at the junction of the relay and the compressor. Even if the relay itself is working properly, a bad contact will not allow the current to pass. Clean the contacts on the compressor and inside the relay with alcohol and a soft cloth. Sometimes simple cleaning brings equipment back to life without buying new spare parts.
Table of typical faults and methods for eliminating them
We will systematize the data received so that it is easier for you to navigate the symptoms. Different manifestations of a malfunction require different approaches to repair. Replacing a relay does not always solve the problem if the root cause of its failure has not been eliminated.
For example, if the relay burned out due to the compressor operating under overload, installing a new device will only lead to a repetition of the situation in a short time. Therefore, always analyze the operating conditions and the condition of the engine itself.
The table below shows the main scenarios that you may encounter during the repair process:
| Symptom | Probable cause | Check method | Solution |
|---|---|---|---|
| Click and silence | Faulty starting relay | Contact dialing | Replacing the relay |
| Humming and shutdown | Thermal protection has tripped | Checking current or temperature | Checking the compressor |
| No response to switching on | Open circuit of protection | Visual inspection and continuity test | Replacement of relay or wiring |
| Frequent on/off | Calibration broken | Monitoring cycles | Replacing the relay |
⚠️ Attention: If, after replacing the relay and checking the windings, the compressor still does not start or the machine in the panel immediately knocks out, there may be a problem in the apartment wiring or in the electronic control module (if there is one). Do not try to endlessly change the relay - this will not help.
Replacement of the relay and final assembly
If the diagnostics confirmed a malfunction, the relay must be replaced. You can buy a new part in spare parts stores for household appliances. It is important to buy a relay with exactly the same markings as the old one. They differ in power, type of fastening and direction of installation. An incorrectly selected relay may not start the compressor or, worse, burn it.
Installation is performed in the reverse order. Push the new relay onto the compressor pins as far as it will go. Make sure it fits snugly and doesn't wobble. Secure it with a bracket or clamp if the design provides for fasteners. Connect the wires (if they were disconnected), following the color markings or photographs taken earlier.
After assembly, do not rush to close the back panel. Plug in the refrigerator and listen. The compressor should start with a characteristic hum, after a few seconds the start relay should click (turn off) and the engine will continue to run smoothly. If the startup was successful, let the equipment run for 15–20 minutes, check the heating of the compressor and the new relay. They should not become red hot.
Is it possible to temporarily start a refrigerator without a relay?
Theoretically, you can apply voltage directly to the working winding, but doing this is strictly not recommended without special skills. You risk burning out the compressor forever or causing a short circuit. It is better to wait for the spare part to arrive.
Frequently asked questions (FAQ)
Is it possible to repair a thermal relay, or only change?
In 95% of cases, relays can only be replaced. This is a low cost consumable. Attempts to clean the contacts or bend the plate back give a temporary effect, after which it is repeated, often with more dire consequences for the compressor.
Why does a new relay burn out a week after installation?
This indicates that the reason was not in the relay itself. Most likely, the compressor is faulty (interturn short circuit, jamming), there are problems with the voltage in the network, or the ventilation of the engine compartment is impaired. The relay simply performs its protection function by acting by itself.
How to distinguish a starting relay from a thermal one?
Often they are combined into one block. Separately: the starting relay usually has a more massive contact mechanism and a posistor (ceramic disk), and the thermal relay has a thin bimetallic plate in a housing with slots for cooling. The starting one works in fractions of a second, the thermal one lasts for minutes and hours.
Where can I find the markings for purchasing an analogue?
The markings are applied to the body of the relay itself (for example, R600, 12862, etc.). You can also find the part number in the technical documentation of the refrigerator or on the manufacturer’s website for the unit model. If the marking is erased, look for the relay according to the compressor parameters.
Is it dangerous to operate a refrigerator with a faulty relay?
Yes, it is dangerous. If the relay does not turn off the compressor when overloaded, the motor will burn out, requiring expensive repairs or replacement of the entire unit. In addition, faulty electrics can cause a fire.