Many owners household appliances are faced with a situation where the refrigerator stops starting, although there is voltage in the network. In 80% of cases, the culprit of the failure is a small component hidden inside the compressor - capacitor. This device is critical for starting the engine, but its physical principle of operation often remains a mystery to users.
If you hear the motor humming, but the shaft does not rotate, or the compressor turns on only for a second and clicks, then the accumulated energy charge is insufficient to overcome inertia. It is this energy that starting capacitorshould provide. Without it, the motor simply cannot go from rest to operating mode.
In this article we will look at what role this element plays in the electrical circuit, how starting and running capacitors differ, and how to diagnose their failure. Understanding the design of the unit will help you avoid an expensive call to a technician or, conversely, will save you from buying unnecessary spare parts.
Principle of operation and role in the electrical circuit
A refrigeration compressor is an asynchronous motor that requires the creation of a rotating magnetic field to start the rotor. An ordinary single-phase network that comes into our socket is not capable of creating such a field on its own. This is where starting capacitorcomes into play. It is connected to the additional stator winding and creates a phase shift between the currents of the main and auxiliary windings.
This phase shift generates the necessary torque. As soon as the motor shaft picks up speed (usually this takes a fraction of a second), the starting winding is turned off. In some modern models of refrigerators Indesit or Atlant a special starting relay is responsible for this, which opens the circuit with the capacitor immediately after start.
It is important to understand that the capacitor does not create energy, but only accumulates and releases it at the right moment. It works as a kind of “spring” in an electrical circuit. If the capacity of the device has decreased due to aging of the dielectric, the “shot” of energy will not be enough to turn the shaft, and the engine will remain humming, trying to start.
⚠️ Attention: When working with the electrical circuit of the refrigerator, always disconnect the device from the network. The capacitor can retain a residual charge even after being turned off, which is dangerous if you touch the contacts with a screwdriver or your fingers.
Some circuits require the presence of two capacitors: a starting and a working one. The worker remains connected to the circuit at all times, helping the motor run stably and reducing energy consumption. However, in household refrigerators, a circuit is most often used only with a starting element, which operates for a short time.
Differences between starting and running capacitors
Often users confuse these two types of devices, although they have significant design and functional differences. Starting capacitor designed for short-term operation (no more than 3-5 seconds) at the moment of switching on compressor. It has a large capacity to provide a powerful starting impulse.
In turn, working capacitor (if it is provided by the design of your refrigerator) functions continuously. Its capacity is usually lower, but it is designed for constant voltage and operation in hot conditions. Using the starting element as a working element is unacceptable - it will quickly overheat and swell.
Is it possible to replace the starting capacitor with a working one?
Replacement is possible only in emergency cases, but with great care. The working capacitor has a smaller capacity, so the start will be more difficult. If the capacity of the working capacitor is too large for the starting circuit, this will lead to overheating of the windings and failure of the compressor.
When selecting a replacement, you must pay attention to the markings. Starting circuits are characterized by capacitance values in the range from 30 to 100 μF and an operating voltage of at least 250-450 Volts. Working capacitors often have a lower capacitance (10-30 µF), but a higher insulation reliability class.
- 🔋 Operating mode: The starting capacitor is turned on for a short time, the working capacitor is turned on permanently.
- ⚡ Capacity: In the starting capacitor it is much higher to create torque.
- 🌡️ Temperature conditions: Workers better tolerate prolonged heat from a running compressor.
Symptoms of a condenser malfunction
Diagnostics of a malfunction often begins with an analysis of sounds, issued by the refrigerator. If you hear a characteristic hum, which ends abruptly with a click of the relay, this is a sure sign that compressor tries to start, but cannot. Most often, the problem lies in a capacitor that has lost capacity or a stuck start relay.
A visual inspection can also tell an experienced technician a lot. A swollen housing, the presence of electrolyte leaks, or a characteristic burning smell indicate that the element has failed. Sometimes the capacitor may look intact, but the internal resistance of the dielectric is no longer normal.
Another symptom is overheating of the compressor. If the motor runs jerkily or tries to start several times in a row, the windings begin to heat up. The thermal relay eventually shuts down the unit to prevent a fire. On-off cycles can be repeated every 10-15 minutes.
It is worth considering that the symptoms may be similar to a malfunction of the compressor itself (interturn short circuit). Therefore, before purchasing a new part, it is recommended to take measurements with a multimeter to avoid more expensive engine damage.
How to check a capacitor with a multimeter
For accurate diagnostics, you will need a digital multimeter with a capacitance test function or at least a resistance testing mode. Before starting work, be sure to unplug the refrigerator from the outlet and remove the protective cover on the back to gain access to the compressor.
Remove the capacitor from the terminals. If there is a residual charge on it, it must be discharged by shorting the contacts with an insulated screwdriver (there will be a spark). Switch the multimeter to the mode of measuring resistance (Ohm) or checking diodes.
Touch the leads of the capacitor with the probes. If the device is working properly, you will see how the resistance begins to increase from zero to infinity (the numbers on the screen will increase). This indicates the charging process. If the resistance immediately shows zero, there is a short circuit inside, if infinity there is an open circuit.
☑️ Diagnosis of the capacitor
The most accurate result will be obtained by measuring capacitance if your multimeter supports such a function. A deviation from the nominal value indicated on the case (for example, marking 30 µF ±5%) by more than 20% indicates the need for replacement. Even if the device “rings”, but the capacitance has dropped to 10 uF, there will be no start-up.
Table of typical parameters of capacitors
When selecting an analogue, it is important to comply with the characteristics. Using a part with less voltage will cause it to explode, and a strong deviation of the capacitance will disrupt the operation of the engine. Below are typical values for household refrigerators.
| Refrigerator type | Compressor power | Capacitor capacity (uF) | Operating voltage (V) |
|---|---|---|---|
| Small (up to 100 l) | up to 100 W | 20 - 30 | 250 - 300 |
| Medium (200-300 l) | 100 - 200 W | 30 - 50 | 300 - 450 |
| Large (400+ l) | 200 - 300 W | 50 - 80 | 450 |
| Industrial | 300+ W | 80 - 120 | 450 - 600 |
Please note that the voltage must be equal to or higher than the rated voltage. If you had a 250 Volt capacitor, and you find a 450 Volt capacitor of the same capacity, it will be even better, since it will last longer. The main thing is that the dimensions allow it to be installed in a regular place.
Modern inverter refrigerators LG or Samsung may not have classic starting capacitors in their usual form, since soft starting there is ensured by an electronic control unit. In such cases, diagnostics are carried out differently.
Replacement process and safety measures
Replacing a capacitor is one of the simplest operations in refrigerator repair, which does not require special tools other than a screwdriver and pliers. The main thing is not to confuse the polarity if the capacitor is polar (although non-polar models are more often used in AC starting circuits).
First remove the old element. It is usually attached to a clamp or inserted into the slots of the starting relay. Disconnect the wires. If the terminals are oxidized, clean them with a knife or sandpaper until shiny. Poor contact can cause repeated failure.
⚠️ Attention: Never leave the wires dangling freely. Vibration from a running compressor can cause a short circuit or broken wiring. Securely secure the connections.
Install a new capacitor by connecting the wires according to the diagram. Often the terminals are marked C (Common), S (Start) or R (Run). If there are no markings, remember or photograph the position of the wires before removing. After assembly, turn on the refrigerator and listen: the startup should be quiet and confident, without a long hum.
If after replacing the capacitor the situation has not changed, and the compressor still hums and clicks, but does not start, there is a high probability of jamming of the piston group or breakage of the windings. In this case, a more complex repair or replacement of the unit will be required.
Frequently asked questions about capacitors
Is it possible to start a refrigerator without a capacitor?
No, in classic circuits with an asynchronous motor, starting without a starting capacitor is impossible. The motor will only hum, consuming current, but the shaft will not rotate, which will quickly lead to burnout of the windings.
Why is the capacitor swollen?
Swelling occurs due to overheating or voltage surges in the network exceeding the nominal value. The reason may also be the end of its service life, when the electrolyte inside the case dries out or reacts with the case material.
How often should the capacitor be replaced?
The service life of high-quality starting capacitors is about 10-12 years or 100,000 switching cycles. In conditions of unstable voltage in the network, this period can be reduced to 5-7 years.
Does the temperature in the room affect the operation of the capacitor?
Yes, extremely high temperatures (above +50°C) can accelerate the degradation of the dielectric. Therefore, it is not recommended to install the refrigerator close to heating appliances or in direct sunlight.