When the refrigerator suddenly stops freezing, the first thought is “the engine has burned out.” But in fact, the compressor starting circuit includes several critical elements, each of which can cause a breakdown. Let's figure out what exactly starts the refrigerator enginehow these components interact with each other, and why sometimes the motor is “silent”, although there is power in the network.
Unlike household appliances that simply turn on (for example, a kettle), the refrigerator works cyclically: the compressor starts and stops dozens of times a day. This process is controlled by a complex system of sensors, relays and electronic boards. An error in at least one link - and the engine will not be able to start, even if it itself is fully operational.
In the article we will analyze in detail:
- 🔧 The main elements of the starting circuit (thermostat, start relay, compressor)
- ⚡ How the engine starts using an example inverter and linear models
- ⚠️ Typical faultsdue to which the motor does not start
- 🔍 Diagnostics at home without special tools
1. Thermostat: the “brain” that gives the command to start
The first (and most underrated) link in the chain is thermostat (or thermostat). This device measures the temperature inside the chamber and closes/opens the electrical circuit, giving a signal to start the compressor. In modern refrigerators (Samsung No Frost, LG Inverter, Atlant two-chamber), instead of a mechanical thermostat, a electronic sensor + control board is often used.
How it works:
- 🌡️ The temperature in the chamber rises above the set value (for example, +5°C instead of +4°C).
- 🔌 The thermostat closes the contacts, passing current to the starting relay.
- ⚡ The relay receives a signal and initiates the start of the compressor.
If the thermostat is faulty, the compressor will not receive a start commandeven though there is power in the outlet. Typical signs of a breakdown:
- 🔴 The refrigerator does not turn on at all (no sounds, indicators do not light).
- 🟡 The motor runs without stopping (the thermostat is “stuck” in the closed state).
- 🔵 B the chamber is too cold or, conversely, warm (incorrect sensor readings).
⚠️ Attention: In refrigerators with No Frost and inverter compressors, the thermostat is often integrated into the electronic board. Replacing it yourself without a circuit can lead to a short circuit.
2. Starting relay: “starter” for the compressor
When the thermostat gives a command, current flows to starting relay a device that short-term supplies increased voltage to the motor windings. Without the relay, the compressor would not be able to overcome the initial resistance and start rotating.
Inside the relay there are:
- 🧲 Coil (creates a magnetic field to close the contacts).
- 🔧 Moving core (closes the starting winding circuit).
- 🔥 Bimetal plate (protects against overheating).
How startup occurs:
- The thermostat closes the circuit → current flows to the working winding of the compressor.
- The relay “feels” the increased starting current and closes the contacts starting winding.
- Engine begins rotation, the current drops → the relay opens the starting winding (only the working winding remains).
| Relay type | Application | Signs of malfunction |
|---|---|---|
| Electromechanical (RTK, RTP) | Old models (ZIL, Minsk, Birusa) | Clicks without starting the engine, burnt contacts |
| Electronic (posistor) | Modern refrigerators (Samsung, Indesit) | The relay heats up, the compressor hums but does not start |
| Inverter | LG, Samsung with inverter compressors | Error on the display (code Er IF, Er dH) |
If the relay fails, the compressor either will not start at allor will beep and immediately turn off (protection is triggered). You can check the relay with a multimeter, but for this you need to know winding resistance your model (data is in the service manual).
3. Compressor: the heart of the refrigerator
Itself compressor is an electric motor with a piston system that compresses the refrigerant (freon) and drives it around circuit. At the moment of startup, it consumes a current of 5–8 times higher than the nominal (for example, instead of 1 A - 5–8 A), so it is impossible to do without a starting relay.
The compressor has two windings:
- 🔵 Working (constantly energized during operation).
- 🟢 Starting (connected only for 1-2 seconds to start).
If the windings are closed or broken, motor:
- 🔴 Does not start at all (break).
- 🟡 It hums and heats up, but does not rotate (turn-to-turn short circuit).
- 🔵 Works intermittently (unstable winding resistance).
⚠️ Attention: Inverter compressors (LG Linear Compressor, Samsung Digital Inverter) do not have a traditional starting relay - its role is played by an electronic unit. It is almost impossible to diagnose such models without special equipment.
How to check a compressor with a multimeter?
To check, disconnect the refrigerator from the network and remove the cover from the compressor terminals. Measure the resistance between the terminals:
- Between C (common) and S (starting winding) → there should be ~20–40 Ohm.
- Between C and R (working winding) → ~10–15 Ohm.
- Between S and R → the sum of the two previous values (~30–55 Ohms).
If the resistance is 0 (short circuit) or ∞ (open), the compressor is faulty.
4. Protective relay: why the motor can turn off immediately after starting
It is often installed next to the starting relay protective relay (or it is built into one device). relay turn off the compressor, If:
- 🔥 The temperature of the windings has exceeded the norm (overheating).
- ⚡ Current consumption is too high (interturn short circuit).
- ❄️ The pressure in the system is higher acceptable (capillary tube clogged).
If the refrigerator turns on for 5-10 seconds and immediately turns off, the protective relay is to blame. Reasons:
- 🔴 The condenser fan is faulty (compressor overheating).
- 🟡 The freon circulation system is clogged.
- 🔵 The temperature sensor on the compressor has failed.
In some models (Atlant, Stinol) the protective relay is combined with the starting relay in one housing. If it works falsely, the motor will “jam” - turn on and off immediately with a characteristic click.
☑️ Diagnostics of the protective relay
5. Electronic control board: the brain of modern refrigerators
In models with No Frost, inverter compressors or a display (Samsung RB37, LG GB-B459) it is responsible for starting the engine. electronic board. It analyzes data from sensors and controls:
- 📊 Temperature in each chamber.
- ❄️ Operation of fans and defrosting heating elements.
- ⚡ Power supply to compressor and relay.
If the board fails, the symptoms can be different:
- 🔴 The refrigerator does not respond to buttons, the display does not light up.
- 🟡 The compressor starts chaotically (for example, every 2 minutes).
- 🔵 There are errors on the display (
Er FF,Er IF,E1).
The most vulnerable elements of the board:
- 🧩 Power relay (often soldered, can burn out).
- 🔌 Voltage stabilizers (burn out during network surges).
- 📡 Temperature sensors (stop transmitting data).
⚠️ Attention: If you decide to replace or solder it, use an antistatic wrist strap and a soldering iron. grounding.
6. Typical startup circuit malfunctions and their symptoms
If the refrigerator does not start, check the symptoms from the table below - they will tell you which element has failed.
| Symptom | Probable cause | How to check |
|---|---|---|
| The refrigerator does not turn on at all (no light, sounds) | The socket, plug, surge protector or control board is faulty | Check the voltage in the socket, inspect the cord for damage |
| The light inside is on, but the compressor does not start | The thermostat, relay is broken or there is a break in the compressor windings | Check the thermostat and relay with a multimeter |
| The compressor is humming, but not rotates | The compressor is jammed or the starting winding does not work | Check the resistance of the windings, rotate the compressor shaft manually (if possible) |
| The motor turns on for 5-10 seconds and turns off | The protective relay (overheating, high current) | Clean the condenser, check the fan, measure the current with clamps |
| The refrigerator works without stopping | Thermostat is stuck or freon leaks | Check the temperature in the chamber, inspect evaporator on ice |
If you are not sure of the diagnosis, do not disassemble the refrigerator at random some breakdowns (for example, freon leakage) require special equipment. In the case of electronic boards, self-repair can lead to irreversible. damage to the firmware.
7. Diagnostics at home: step-by-step instructions
Before calling a technician, you can check the basics yourself. elements. For this you will need:
- 🔧 Screwdriver (Phillips/flat head).
- 📊 Multimeter (to check resistance).
- 🔌 Voltage tester (or indicator screwdriver).
Step 1. Check power supply
- 🔌 Make sure that there is voltage in the outlet (220–230 V).
- 🔌 Check the cord and plug for damage.
- 🔌 If the refrigerator is through a surge protector, connect directly.
Step 2. Checking the thermostat
- 🔧 Remove the temperature regulator (usually located inside the chamber).
- 📊 Call the contacts with a multimeter in resistance mode.
- 🔄 When rotating the knob, the resistance should change from
0(closed) on∞(open).
Step 3. Checking the relay and compressor
- 🔧 Turn off the refrigerator, remove the cover from the compressor terminals.
- 📊 Measure the resistance between conclusions
C-S,C-R,S-R. - 🔧 Inspect the relay for burnt contacts or cracks.
Step 4. Visual inspection
- 🔍 Check whether the condenser fan rotates (if any).
- ❄️ Make sure that the There is no thick layer of ice on the evaporator (it can block the sensor).
- 🔥 Clean the rear grille from dust (overheating of the compressor is a common cause of shutdowns).
FAQ: Frequently asked questions about starting the refrigerator engine
❓ Why does the refrigerator click but does not start?
It makes clicking noises starting or protective relay. Reasons:
- 🔴 The relay is faulty (contacts are burnt, the spring is broken).
- 🟡 The compressor is jammed (the windings need to be checked).
- 🔵 Overheating protection is triggered (check the condenser fan).
If clicks are repeated every 5-10 seconds, most likely the relay or the compressor itself is to blame.
❓ Is it possible to start the compressor without a relay?
Technically possible, but is highly not recommended. Without a relay, the starting winding will not receive the required current, and the motor:
- 🔥 It will overheat and burn out.
- 💥 May cause a power surge in the network.
- ⚡ Does not develop the required power (will not freeze).
If the relay is broken, it is better to replace it with a similar one.
❓ Why does the new refrigerator not start after delivery?
Possible reasons:
- 🔌 Transport bolts not removed (blocking the compressor).
- 📦 The power cord or plug is damaged.
- ⚡ There is no voltage in the socket or there is no voltage too low (<190 V).
- ❄️ The refrigerator was turned on immediately after delivery - you need to wait 2-4 hours (the oil in the compressor must drain).
❓ How to check if the compressor is working if it does not start?
Ways diagnostics:
- 📊 Continuity of the windings multimeter (resistance should be in the range of 10–50 Ohms).
- 🔧 Checking for interturn short circuit (if the resistance between the housing and the terminals is not equal to ∞).
- 🔊 Listening: a working compressor emits a smooth hum when turned on, a faulty one produces rattling or clicking sounds.
If the windings are in order, but the motor does not start, the problem is in the relay or control board.
❓ Can the refrigerator not start due to a power surge?
Yes, voltage surges is one of the main causes of breakdowns:
- 🔥 The control board burns out (especially in Samsung i LG).
- 🔌 The compressor relay fails.
- ⚡ The motor windings burn out (less often, but possible).
To protect the refrigerator, use voltage stabilizer or voltage control relay (for example, Zubr or Digitop).