The situation when the refrigerator stops cooling, and there is warm silence inside its chambers, is familiar to many owners of household appliances. The most common reason for the lack of cold is faulty compressor, which simply refuses to start. This is the heart of your refrigeration unit, and if it stops, the entire cooling cycle is disrupted instantly.
Before you panic and call a technician, it is worth conducting an initial diagnosis. Often the problem lies not in the breakdown of the motor itself, but in the control chain or protective mechanisms. In this article we will examine in detail why the unit hums, but does not startand how to identify the culprit of the breakdown yourself.
It is important to understand that modern models, be it Indesit, Atlant or Bosch, may have different designs of starting devices. However, the basic operating principles remain similar. If you notice that the refrigerator turns on and immediately turns off, or there is absolute silence, you need to check the electrical circuit.
⚠️ Attention: Carry out any work on disassembling the refrigerator and checking the electrical contacts only with the power completely disconnected from the network. Electric shock can be fatal.
Main causes of compressor failure
Failure to start the motor can be caused by many factors, from a simple power surge to a complex breakdown of electronics. Most often, the culprits are the start relay or thermostat, which stops sending a start signal. If starting relay is stuck or burnt out, the motor windings do not receive the necessary impulse.
Another common cause is a malfunction thermostat. This sensor monitors the temperature inside the chamber and gives a command to turn the compressor on or off. If it is “stuck” in the “off” position, the motor simply will not receive a signal to operate, even if the chamber is warm.
- 🔌 Voltage surges: Sudden changes in the network could damage the electronic control board or burn the motor windings.
- ❄️ Sensor malfunction: V models with No Frost, the defrost sensor often fails, blocking the start of the compressor.
- 🔥 Overheating: If the refrigerator is close to the wall, the motor may go into protection due to overheating.
It is also worth mentioning interturn short circuit windings of the compressor itself. This is the most unpleasant scenario in which the engine hums, heats up, but cannot start, since the current in the windings is distributed unevenly. In such cases, thermal protection is often triggered.
Diagnostics of the starting relay and thermostat
The first thing when looking for the reason why the compressor does not turn on, you need to check the starting relay. It is this small element that is responsible for supplying voltage to the starting winding at the moment of start. If the relay is faulty, you can hear characteristic clicks, but startup does not occur.
To check the relay, it must be removed and shaken. If a ringing sound is heard inside, it means that the core or mechanism has collapsed, and the part must be replaced. Also, the contacts could oxidize or burn, which impairs the conductivity of the current. In models with electronic control, the role of the relay is played by the board, but the principle remains the same.
The thermostat is tested by shorting its contacts. If, when the thermostat wires are shorted (bypassing the sensor itself), the compressor starts, then this is where the problem lies. This is a common situation for refrigerators Stinol and Liebherr old model.
⚠️ Attention: Closing the thermostat contacts for testing is only permissible for a short time (literally a couple of seconds) to make sure the motor is working. Long-term operation without a thermostat will lead to freezing of the evaporator.
Problems with windings and interturn short circuits
If the starting device and thermostat are working properly, and the compressor still hums and clicks, but does not start, there is a high probability of problems with motor windings. Interturn short circuit is a violation of the insulation between the turns of the coil, which leads to a sharp increase in current and tripping of the protection.
You can check the integrity of the windings using a multimeter. It is necessary to test the resistance between the contacts. Normal resistance values vary, but if the meter reads "zero" (short circuit) or "infinity" (open), the compressor is faulty. It is also worth checking the resistance between the case and the contacts - there should be no conductivity there.
| Type of fault | Multimeter readings | Symptoms | Solution |
|---|---|---|---|
| Open circuit | Infinity (1) | Silence, no buzzing | Replacing the compressor |
| Short circuit | Zero (0) | Knocks out plugs | Replacing the compressor |
| Breakage to the housing | There is resistance | Electric shock when touched | Urgent replacement |
| Normal | 10-30 Ohm | Stable operation | No repair required |
It is important to note that it is almost impossible to restore burnt windings at home. Attempts to rewind the compressor motor are economically impractical and technically difficult, therefore, in 99% of cases, a complete replacement of the unit with a new one is required.
Faults in refrigerators with No Frost
System owners No Frost We often encounter a situation where the compressor does not turn on due to problems with the defrost system. If the evaporator heating element is burnt out or the defrost sensor is faulty, a “coat” of ice builds up on the evaporator. The fan stops spinning and the temperature sensor may block the compressor from starting to prevent overheating.
In such models, for example Samsung or LG, it is important to check the defrost timer and defrost sensor. If the system is stuck in defrost mode, the compressor will not receive a cooling command. Often, completely defrosting the refrigerator during the day helps.
The hidden reason for blocking in No Frost
In some models, if the air duct damper or damper motor is faulty, the electronics may mistakenly block the operation of the compressor, believing that the temperature has been reached.
It is also worth paying attention to the fan. If it does not turn due to icing or damage, the sensors may give incorrect readings. Checking the integrity of the fan circuit is a mandatory diagnostic step.
Electronic control board and inverter motors
Modern refrigerators are controlled electronically. If you inverter compressorworks smoothly and quietly, then a complex control module is responsible for its startup. Unlike older models, there is no classic starting relay.
When voltage surges occur, the control board or the inverter unit itself suffers first. The symptom may be an attempt to start, followed by an error on the display or a characteristic sound signal. Diagnostics of such systems requires special knowledge and equipment.
- 💻 Software failure: Sometimes the control module requires flashing or resetting errors.
- ⚡ Burnt module: Visually noticeable burn marks on the control board.
- 📡 Communication problems: In dual-compressor models, communication between the boards may be disrupted.
⚠️ Attention: Repair of inverter systems and replacement of electronic boards often require resoldering components or purchasing expensive original modules. The cost of such repairs can be up to 50% of the price of a new refrigerator.
Step-by-step instructions for checking the circuit
If you decide to carry out diagnostics yourself, follow a clear algorithm of actions. This will help avoid mistakes and injuries. Remember that safety comes first, and if you are not confident in your abilities, it is better to turn to professionals.
☑️ Troubleshooting algorithm
Start with a visual inspection. Are there any melted wires, blackened contacts or traces of moisture? Then check the voltage at the compressor inlet (experienced only!). If there is voltage, but the motor does not turn, the problem is in the motor or relay. If there is no voltage, we look in the control circuit.
When you need to call a technician
There are situations when independent repair is impossible or dangerous. If the compressor itself needs to be replaced, it is necessary to have special equipment: a burner, a vacuum pump, a pressure gauge station and refrigerant. You cannot simply “change the motor” without vacuuming the system - the refrigerator will not work.
Also, technicians are needed to find freon leaks. If the compressor is working properly, but there is no cold, there may be no refrigerant in the system. Detection of microcracks in the foamed housing or in the evaporator requires a professional approach and tools.
Do not ignore warranty obligations. If your refrigerator is less than 3-5 years old, any DIY repair will void your warranty. In this case, the only correct solution is to call the manufacturer’s authorized service center.
Why does the compressor hum for 5-10 seconds and turn off?
This is a classic symptom of a jammed compressor or an interturn short circuit. The motor tries to start, the current increases sharply, and the thermal protection relay opens the circuit to prevent a fire. Also, the cause may be a critically low voltage in the network.
Is it possible to start the compressor bypassing the relay?
Technically, you can start it by applying voltage directly to the working and starting windings, but this should only be done for diagnostics (for 1-2 seconds). Constant operation without a starting device will lead to burnout of the motor windings.
What to do if, after a light surge, the refrigerator stops freezing?
Most likely, the starting module has failed or the control board has burned out. First check the fuse (if equipped) and the start relay. If they are intact, electronics diagnostics will be required.
How to understand that the thermostat has burned out?
If you turn the thermostat knob to the maximum, knock on it, but the refrigerator does not turn on, and the contact test shows a break - the thermostat is faulty. In electronic models, this is often indicated by an error code on the display.