Has the refrigerator stopped freezing, but the motor hums only for a few seconds and then goes silent? Or does the compressor show no signs of life at all, although the light in the chamber is on? In most such cases, the culprit is starting relay a small but critical element of the electrical circuit. It is he who is responsible for starting the engine, supplying a short-term impulse to the starting winding, and turns it off when the motor reaches the required speed.
Diagnostics of this unit does not require complex equipment or deep knowledge in electronics. A basic understanding of the operating principles of refrigeration equipment and a simple tool such as a multimeter is sufficient. In this article we will look at how to independently determine the malfunction, why the relay burns out and whether it is worth trying to repair it.
Before you start disassembling, make sure that you follow the electrical safety rules. Working with live electrical appliances is unacceptable, so the first step should always be to disconnect the device from the mains. This simple action will protect you from electric shock and prevent a possible short circuit in case of an error when manipulating the wires.
Principle of operation and types of relays
The starting relay is a switch that is activated when the refrigerator is turned on. When you connect the unit to the network, current passes through induction coil or the heating element (depending on the type of relay), creating a magnetic field or thermal expansion. This action closes the contacts, applying voltage to the compressor start winding. As soon as the motor rotor begins to rotate, the current drops and the relay opens the circuit, leaving only the main winding to work.
There are two main types of devices used in household appliances: induction (electromagnetic) and posistor (thermal). Induction relays work due to electromagnetic force, which draws in the core and closes the contacts. They are typical for older models of refrigerators and often have a vertical orientation when installed. Posistor relays they use the property of semiconductor material to sharply increase resistance when heated. They are considered more reliable and modern, are installed horizontally and do not have moving mechanical parts in the classical sense.
⚠️ Attention: Mixing up relay types when replacing can lead to combustion of the compressor. An inductive relay will not work in a circuit designed for a posistor, and vice versa. Always check the markings.
In addition to the starting function, the relay is often located thermal protective relayon the body. It monitors the compressor case temperature and amperage. If the motor overheats or an overcurrent occurs, the bimetallic strip inside opens the circuit, stopping the unit until it cools down. Often these two elements are combined into one unit, which simplifies installation, but requires replacing the entire assembly if any of its parts break down.
External signs of a malfunction
You can determine that the problem lies in the trigger mechanism by the characteristic symptoms that appear immediately after switching on refrigerator to the network. The most common symptom is the so-called “clicking”. You hear a loud click, the engine tries to start, hums for 2-3 seconds, then a second click is heard, and there is silence. After some time, the cycle repeats. This indicates that starting relay cannot keep the contacts closed or does not close the starting winding circuit.
Another alarming symptom is the absence of any sounds from the compressor. The refrigerator is on, the light inside is on, but the motor is silent. In this case, it is possible that the relay contacts have oxidized or become so burnt that current simply does not pass to the motor windings. Sometimes, in this case, heating of the relay itself or the appearance of a smell of galling wiring may occur, which indicates an overload.
- 🔊 A loud click followed by silence and repeating the cycle after 20-40 seconds.
- 🔥 The smell of burnt plastic or scorched wiring in the compressor area.
- 🧊 The compressor is warm or hot to the touch, but no cold is generated in the chamber.
- 📉 Broken plugs or the machine in the control panel is triggered when the refrigerator is turned on.
It is important to distinguish between a relay failure and a malfunction of the compressor itself. If the motor hums but does not start, and the relay is working properly, the piston group may be jammed or an interturn short circuit has occurred in the motor windings. However, statistics show that in old refrigerators it is the starting equipment that most often fails, and not the “heart” of the unit itself.
Dismantling and visual inspection
To carry out diagnostics, you need to gain access to the compressor. It is usually located at the bottom rear of the refrigerator. Remove the protective cardboard or plastic panel by removing the mounting screws or latches. Before touching any parts, make sure that the power cord is unplugged from the outlet. Visual inspection can immediately answer the question about the cause of the breakdown.
Carefully remove the relay from the compressor contacts. It is usually fixed to the three terminals of the motor and held in place by a spring clip or plastic bracket. In some models, for example Indesit or Atlant, you may need to remove the retaining frame. Inspect the body of the device: there should be no cracks, traces of soot or melted plastic. If you see black spots or smell a burning smell, the element definitely requires replacement.
☑️ Check before disassembly
Pay special attention to contacts. If they are covered with oxide or carbon deposits, this creates a high contact resistance that interferes with normal starting. In some cases, the contacts can be cleaned, but if the plastic around them is deformed due to temperature, it is better not to risk it. Also check the integrity of the wires going to the relay: they should not be broken or melted.
Diagnostics with a multimeter
The most accurate way to check the operation of the unit is to use a multimeter in resistance measurement mode (Ohm). This method allows you to evaluate the condition of internal circuits and contacts without connecting the device to the network. Switch the device to the 200 Ohm range or dialing mode. If you have a posistor relay, at room temperature it should show a resistance in the range of 10-60 Ohms (the value depends on the specific model).
For induction relays the procedure is a little more complicated. It is necessary to ring the contacts corresponding to the starting winding. In the normal state (horizontal position), the resistance between the contacts should be close to zero, and when the relay is turned over, there should be a gap (infinity). This checks the mechanical part: whether the core moves and whether the contacts close. If the multimeter shows “1” (open) in both positions or “0” (short circuit) where it should not be, the part is faulty.
The thermal relay also needs to be checked. Ring its contacts: when cold they should ring (resistance is close to 0 Ohm). If the device shows a break, it means that the bimetallic plate has already broken the circuit and does not return, or the heater coil has burned out. In this case, the compressor will not receive power at all.
What to do if you don’t have a multimeter?
If you don’t have a tester at hand, you can try to gently shake the relay near your ear. If a rattling sound is heard inside (as from broken ceramics), it means the posistor or contacts are damaged. However, this method does not provide a 100% guarantee, since the internal contacts may simply be burnt, but physically intact.
Don't forget to check the compressor itself to make sure that it is not the problem. Ring the three contacts on the motor (usually labeled C, S, R or just dots). The resistance between pairs of contacts should be approximately the same or differ by 1.5 times. If you see a short circuit to the housing (one probe to the contact, the second to the copper tube or housing), the compressor is broken and requires replacement.
Table of resistance values and states
For ease of diagnosis, we will summarize the main readings of the multimeter and their interpretation in a table. This will help you quickly navigate the measurement results and make the right decision on repairs.
| Type of check | Multimeter readings | Probable cause | Action |
|---|---|---|---|
| Posistor (if 20°C) | 10 - 60 Ohm | Normal | Look for the cause elsewhere |
| Posistor | 0 Ohm or ∞ (infinity) | Short circuit or break inside | Replacing the relay |
| Thermal relay | ∞ (infinity) | The spiral or contacts burned out | Replacing the relay |
| Induction contacts | ∞ in any position | Open circuit or jamming | Replacing the relay |
It is worth noting that the resistance of the posistor strongly depends on temperature. If you just turned off the refrigerator and it is hot, the resistance will be high. Let it cool to room temperature before checking. Measurement accuracy critical: an error of a few ohms may be acceptable, but a complete lack of conductivity or a short circuit is always a sign of a defect.
⚠️ Attention: When checking, do not hold multimeter probes with your fingers simultaneously on the metal parts, if the device is energized (although in this case we are checking a disconnected device, the habit must be developed).
Replacement and selection of a new relay
If diagnostics have confirmed a malfunction, the only correct solution is to replace the element. Repairing a starting relay, especially a posistor relay, is not economically feasible and technically difficult. The sealed case is difficult to open without damage, and it is almost impossible to find a similar posistor inside. It is better to purchase a new assembly.
When purchasing, pay attention to the markings. It must match the original or be its complete analogue. Consider the power of the compressor (indicated on the motor nameplate, for example, 1/4 HP, 1/3 HP) and the type of refrigerant (R134a, R600a), although the latter rather affects the compressor itself, but the relays are selected for specific series of motors. Popular brands, such as Danfoss, Secop or Start, produce universal models suitable for many refrigerators.
Installing a new relay is simple: it is placed on three pins of the compressor. It is important to orient the part correctly: usually there is an arrow “UP” or “TOP” on the body, which should face up. Also check that the wires do not touch the hot compressor pipes. After installation, secure the fixing frame or bracket.
Common mistakes during DIY repairs
Home craftsmen often make mistakes that can aggravate the situation. One of the most common is an attempt to “revive” an old relay by cleaning the contacts with sandpaper without replacing the mechanism itself. In induction relays this can give a temporary effect, but in posistor relays there is simply nothing to clean - there is a chemical process there. In addition, violation of the geometry of the contacts will lead to the relay constantly sparking.
Another mistake is ignoring the cause of the burnout. If a relay burns out, this is often a consequence, not a cause. The compressor may be cranking hard due to thickened oil or valve problems, which creates a higher than normal starting current. Or there are power surges in the network. Installing a new relay without eliminating the root cause will lead to its re-burning in a short time.
- 🚫 Trying to start the compressor directly, bypassing the relay (can burn the winding).
- 🚫 Installing a relay inappropriate power (too powerful will not turn off the starting winding).
- 🚫 Ignoring the state of the capacitor (if it is in the circuit), which also affects the start.
Also, do not neglect checking the wiring. If the insulation of the wires going to the relay is melted, they must be replaced or carefully insulated. A short circuit in this area can damage not only the new relay, but also the wiring in the wall.
Precautions and safety
Working with refrigeration equipment involves risks. In addition to electric shock, there is the danger of cuts from sharp edges of metal panels and burns from a hot compressor. Always wear gloves and use tools with insulated handles. Remember that refrigerant circulates in the system, and although its amount in domestic refrigerators is small, damage to the tubes can lead to gas leakage.
If you notice that the cooling system tubes (copper or aluminum) have signs of corrosion or mechanical damage, do not try to carry out repairs yourself without the skills of soldering and vacuuming the system. In this case, it is better to call a specialist. Independent manipulations can lead to complete failure of the refrigerator.
⚠️ Attention: Never turn on the compressor without load (without freon and condenser) unless you carry out specialized diagnostics with pressure gauges. Working “dry” can quickly damage the valve apparatus.
Following these simple rules will allow you to safely carry out diagnostics and, if necessary, replace the relay, restoring life to the refrigerator. If after replacing the relay the situation has not changed, the problem probably lies deeper - in the compressor itself or the control system, which requires professional intervention.
How much does a start relay for a refrigerator cost?
The cost depends on the model and manufacturer. For domestic refrigerators (Atlant, Biryusa) the price ranges from 300 to 800 rubles. For imported brands (Indesit, Bosch, LG) the price can vary from 800 to 2500 rubles. Universal relays are cheaper, original ones are more expensive.
Is it possible to start a refrigerator without a relay?
Theoretically, you can start it by applying voltage directly to the starting winding for a short time, but it is absolutely impossible to operate the refrigerator in this mode. The compressor will burn out in a few minutes or even seconds due to lack of protection and proper switching of the windings.
Why does the relay constantly burn out?
Frequent reasons: unstable voltage in the network, compressor wear (hard start), incorrectly selected relay power or poor contact in the electrical circuit, causing sparking and heating.
How to understand that it was the posistor that burned out, and not the thermal relay?
You need to ring them separately. A posistor in a cold state has a resistance (10-60 Ohms), a thermal one - almost 0 Ohms. If the posistor shows a break or zero, it is faulty. If the thermal signal does not ring, the problem is in the protection. They often change as an assembly.
Where is the relay located on the compressor?
It is located on the side of the compressor, covered with a plastic or metal casing. To get there, you need to move the refrigerator away from the wall, remove the back panel at the bottom and unscrew/remove the cover above the motor.