A sudden stop of the refrigerator often becomes an unpleasant surprise, especially when perishable foods are stored in the chamber. The compressor may hum but not start, or it may turn on for a few seconds and then go silent again. In most such cases, the culprit of the malfunction is starting relay, which is responsible for starting the compressor engine.
This small but critical part provides voltage to the starting winding at the time of start and turns it off after gaining speed. If you notice that your Atlant refrigerator or Indesit has stopped cooling, and the compressor only clicks, do not panic. Replacing this component is one of the most accessible procedures in the repair of household appliances, which you can do yourself if you have basic tools and follow safety precautions.
In this article we will analyze in detail the device of the starting mechanism, diagnostic methods and the algorithm of actions for replacing it. A correctly selected and installed part will bring your equipment back to life without the need to call an expensive technician.
Design and principle of operation of the starting relay
The starting relay is an electromechanical switch that works in conjunction with a thermal protection relay. The main task of the device is to briefly supply current to the starting winding of the asynchronous compressor motor. When the refrigerator is turned on, the motor rotor is stationary, and moving it from its place requires significant force, which is created by the starting winding. As soon as the engine reaches the required speed (usually 75% of the nominal), the relay opens the starting winding circuit, and the engine continues to operate only on the working winding.
There are two main types of devices found in modern and older models. The first type is induction (electromagnetic) relay. They have a movable core, which, under the influence of current, is drawn in and closes the contacts of the starting winding. As the speed increases, the current drops, the core lowers under the influence of gravity and opens the circuit. The second type is posistor (PTC) relay. They use a ceramic element (posistor), which, when heated, sharply increases its resistance, actually breaking the circuit. Such models are more reliable and do not have moving mechanical parts.
What is the difference between a posistor and an electromagnetic relay?
Posistor relays are cheaper, more compact and work Quieter because there are no moving contacts that could spark or stick. However, they are sensitive to overcurrent and can fail if the voltage is unstable. Electromagnetic relays are more durable in conditions of power surges, but over time their contacts can oxidize or burn, and the mechanism itself can jam.
The thermal relay, which is often combined into one housing with the starting one, serves as a fuse. It opens the compressor power circuit if the current exceeds the permissible limits or if the engine overheats. This prevents the motor windings from burning out when jammed or other malfunctions.
Fault diagnosis: signs and testing
Before going to the store for a new part, you need to make sure that the problem lies in the relay. There are several characteristic symptoms indicating its failure. Often the compressor makes a loud click, tries to start, hums for 3-5 seconds, then a second click is heard and the motor goes quiet. After some time, the cycle repeats. This is a classic sign that the starting winding is not receiving an impulse or is not turning off in time.
For an accurate diagnosis, you will need a multimeter. Before starting any work be sure to disconnect the refrigerator from the power supply. Remove the rear protective cover at the bottom of the unit where the compressor is located. Carefully remove the plastic housing from the relay and heat sensor. Disconnect the wires and remove the relay from the compressor. Visually inspect the case: the presence of melts, cracks or traces of burning clearly indicates the need for replacement.
- 🔍 Shake the relay near your ear: if you hear a knocking sound from the internal element, it means the mechanism is damaged and requires replacement.
- 🔌 Call the contacts: in the initial position, the contacts of the working winding should ring, and the starting circuit - depending on the type of relay.
- 🌡️ Check the thermal relay: its contacts in a cold state should be closed (resistance close to zero).
If a visual inspection and testing with a multimeter do not reveal obvious breaks, but the refrigerator does not start, It is often easier and cheaper to replace the relay with a new one, since internal defects of the posistor or sticking contacts are not always detected by the device.
Preparation for replacement: tools and safety
Replacing the start relay does not require complex specialized equipment, but requires precautions. The main danger is electric current and possible high pressure in the refrigerant system, although when replacing the relay we do not affect the sealed circuit. However, careless handling of wires or tools can damage copper tubes, which will lead to freon leakage and expensive repairs.
For work you will need:
- 🛠️ A set of screwdrivers (Phillips and flat) for removing the casings.
- 🔧 Pliers or pliers for removing terminals.
- 🧤 Dielectric gloves (recommended).
- 📸 Smartphone for photographing the wiring diagram.
⚠️ Attention: It is strictly forbidden to bite or bend the copper tubes coming from the compressor. They are very thin and break easily. Carry out all manipulations only with the electrical part (wires, terminals, plastic case).
It is also important to ensure good lighting of the work area. Dust and dirt often accumulate at the bottom of the refrigerator, so before starting work, it is recommended to vacuum the area around the compressor so that debris does not get inside the relay mechanism or onto the contacts.
Step-by-step instructions for removing and installing the relay
The replacement process begins with dismantling the faulty part. Once you have removed the compressor protective cover, you will see a box that fits directly onto the three pin studs coming out of the motor housing. This box is our start relay, often combined with a thermal release. It can be fixed with a metal bracket or simply sit tightly on the contacts.
Before pulling the relay Take a photo of the location of the wires. Insulation colors may differ in different refrigerator models (Bosch, LG, Stinol), and it is very easy to confuse them. If the wires have terminals, carefully remove them from the relay contacts by gently wiggling them from side to side. Do not pull sharply so as not to break the wire at the base.
☑️ Algorithm for replacing the relay
Remove the relay from the compressor studs. Pay attention to the orientation: the case often has marking UP (top) or an arrow pointing up. This is critical, especially for electromagnetic relays where the core must move vertically under the influence of gravity. Installing such a relay upside down will cause it to not work correctly.
Install the new relay in the same orientation as the old one. Push it onto the three studs until it stops. Make sure it fits snugly and doesn't wobble. Then connect the wires to the corresponding terminals, focusing on the photo you took earlier. Check the reliability of the connection: the terminals should not fall off when slightly pulled.
| Relay type | Orientation during installation | Characteristic sound | Sensitivity |
|---|---|---|---|
| Electromagnetic | Strictly vertical (arrow up) | Loud click when starting | Low (resistant to surges) |
| Posistor (PTC) | Any (usually repeats the old) | Silence or quiet crackling | High (afraid of overloads) |
| Combined | By body marking | Click + silence | Medium |
After installing all the elements, return the metal retaining bracket (if there was one) and close the protective plastic casing compressor. Make sure that the wires do not touch hot parts of the compressor or moving elements (if there is a fan).
Typical errors when connecting
Even a simple operation can be performed incorrectly if the details are ignored. One of the most common mistakes is incorrect relay orientation. As mentioned earlier, electromagnetic devices operate using gravity. If you install such a relay sideways or upside down, the core will not be able to move down and break the starting winding circuit. This will cause the starting winding to be constantly energized, which will cause it to overheat and burn out.
Another common problem is poor contact in the terminals. If you do not fully insert the terminal onto the stud of the new relay, transition resistance will arise at the connection point. This will cause local heating, melting of the plastic and eventually sparking. In the worst case, this can cause a fire.
⚠️ Attention: Never leave the compressor without a protective casing for a long time. The casing not only protects from dust, but also directs air flow to cool the engine. Working without it can lead to overheating and tripping of the thermal relay.
It is also a mistake to ignore the state of the thermal relay. Often, when replacing the starting element, they forget to check the thermal protection. If it is faulty (does not ring or, on the contrary, is constantly closed under any conditions), the new starting element will also not be able to start the compressor or will not protect it in the event of an accident.
Checking operation after replacement
After installation is completed, the most exciting moment comes - the first start-up. Plug in the refrigerator. In the first seconds, you can hear the characteristic click of the relay (if it is electromagnetic) and the hum of the compressor starting up. If the engine starts running smoothly, without vibrations or extraneous sounds, and after 5-10 minutes the condenser tubes (usually located on the sides or rear) begin to get warm, then the replacement was successful.
Pay attention to the operating cycle. The compressor must work for a certain time (from 10 to 40 minutes depending on the settings and temperature in the chamber), then turn off. If it works without stopping for more than an hour, there may be little freon in the system or the seal is broken, and the relay has nothing to do with it. If the compressor clicks again and stops after a couple of seconds, then the problem is deeper: perhaps the motor itself is faulty (interturn short circuit) or the piston is jammed.
During the first day of operation, it is recommended to periodically check the temperature in the chambers and monitor the heating of the compressor. It should be hot, but not scalding. Excessive heating of the relay body is also unacceptable.
What to do if, after replacing the relay, the refrigerator does not start?
If the situation has not changed after installing the new part, check the voltage in the socket. If the network is normal, the compressor itself may be faulty (breakdown to the housing or broken windings). It is also worth checking the wiring going to the thermostat or electronic control module, since the start signal may not come from there.
Is it possible to start a refrigerator without a start relay?
Theoretically, you can start an asynchronous motor manually by spinning the shaft, but in domestic conditions this is impossible and extremely dangerous. Without a relay, the starting winding will either not turn on (the engine will not start and will hum), or will burn out if voltage is applied to it directly without automatic shutdown.
How long does a starting relay last?
The average service life of a high-quality relay is 5-10 years. However, frequent power surges, temperature surges and vibrations can shorten this period. PTC elements are considered more durable with a stable power supply, but they do not like frequent switching on and off (for example, if the refrigerator is often opened or it is standing next to a heat source).
Where to buy a suitable relay?
It is best to look for the part according to the markings indicated on the body of the old relay. You can buy it in specialized stores of spare parts for household appliances, on radio markets or in online stores. Universal relays are not always suitable, so it is better to take the original or a complete analogue for your compressor model (for example, Danfoss, Secop, Aspera).
Is it dangerous to change the relay yourself?
If you follow safety precautions (disconnect from the network, do not touch the copper pipes), the risk is minimal. The main danger is electric shock when the cord is turned on or damage to the cooling system. If you are not confident in your forces, it is better to contact a professional.