The situation when the refrigerator stops cooling, and the compressor either hums, but does not start, or makes a short click and goes quiet, often indicates a problem in the trigger circuit. One of the main suspects for this fault is the starting capacitor. This small but critical element provides the necessary phase shift to start the compressor motor. If its capacity drops or a breakdown occurs, the motor simply cannot overcome the initial inertial resistance.
Diagnostics of this element does not require deep knowledge in electronics, but requires strict adherence to safety precautions and the availability of basic tools. Capacitor can fail both due to voltage surges in the network and due to the natural aging of the electrolyte inside the housing. Understanding exactly how the test takes place will allow you to save time on calling a technician, or at least accurately diagnose the problem before purchasing spare parts.
In this article we will analyze all the nuances of the test: from visual inspection to precise measurements with a multimeter. You will learn which values are considered normal and which indicate the need for replacement. We will also touch on the topic of selecting analogues if the original part could not be found. Remember that incorrect operation of the starting device can lead to overheating of the compressor windings, so signs of malfunction cannot be ignored.
Symptoms of malfunction and visual diagnostics
Before taking up measuring instruments, you should conduct a thorough external inspection. Often defects are visible to the naked eye. If your refrigerator hums but does not turn on, or turns on for a few seconds and turns off via a thermal relay, these are the first bells. Visual diagnostics allows you to weed out clearly damaged elements without unnecessary manipulations with the tester.
Remove the protective cover from the compressor (usually at the bottom back refrigerator) and get to the start relay. The capacitor is often attached directly to the relay body or located inside a plastic box. Remove it by first photographing the connection diagram so as not to confuse the wires during assembly. Pay attention to the following defects:
- 🔥 Bloating of the upper part of the case or rupture of the safety notch (cross) at the end.
- 💧 Leakage of electrolyte: the presence of oily stains on the capacitor itself or the board nearby.
- ⚡ Traces of soot, burning or melting of contacts at the place of soldering or terminal connection.
- 🔨 Mechanical damage to the housing: cracks, chips, deformation from impact.
⚠️ Attention: Even if the capacitor looks perfect on the outside, this does not guarantee its serviceability. Internal breakage or loss of capacity (drying out) is not visually detected. Always carry out an instrumental check.
If you find swelling or traces of leakage, further measurements may be unnecessary - the part requires replacement. However, if the case is clean and intact, this is not yet a reason to rejoice. Polypropylene and electrolytic capacitors tend to lose capacity over time without external signs. That is why the next stage - measuring the parameters - is mandatory.
Required tools and safety measures
For high-quality diagnostics, you will need a minimum set of tools that any home craftsman can find. The main device will be multimeter (tester). It is desirable that it have a capacitance measurement function (indicated as Cx or F), but you can also get by with a resistance measurement mode. A screwdriver, pliers and possibly a soldering iron will also come in handy if the capacitor is soldered into the board and not connected through terminals.
Safety is priority number one. Although there is no voltage in the 220 volt network when the refrigerator is turned off, charges may remain in the circuit. In addition, there is a risk of short circuit if the tester probes are not handled carefully. Before starting work, be sure to follow these steps:
- 🔌 Disconnect the refrigerator from the power supply by unplugging the plug from the socket.
- ⏳ Wait 5-10 minutes after disconnecting for the high-voltage elements to discharge.
- 🧤 Use a tool with an intact insulation of handles.
- 🧼 Ensure dry hands and work surface to avoid false readings from the device.
When working with a multimeter, it is important to set the mode correctly. If you are measuring resistance, choose a limit of 20 kOhm or 200 kOhm. To check the capacity, the switch is placed in the appropriate sector. Do not touch the metal parts of the probes with your hands during measurements, as the resistance of the human body can distort the results, especially at high measurement limits.
☑️ Preparation for testing
Checking the capacitor with a multimeter in ohmmeter mode
The most accessible method of testing, available even on cheap models testers is measuring resistance. This method allows you to detect a short circuit inside the plates or a complete break. Switch the multimeter to resistance measurement mode (200 kOhm limit or maximum available). Connect the probes to the terminals of the capacitor.
In a working electrolytic or starting capacitor, you will see the needle of an analog device or the numbers on a digital display begin to grow rapidly, indicating an increase in resistance. This is the process of charging the capacitor from the tester battery. As a result, the resistance should go to infinity ( 1 or OLwill appear on the screen). If the device shows zero or very low resistance, there is a breakdown.
However, this method has its limitations. It detects short circuits well, but does not detect loss of capacitance well. The capacitor may charge and show an increase in resistance, but its actual capacity may be 10% of the nominal value, which is not enough to start the compressor. For more accurate diagnostics, a capacitance measurement mode is required.
⚠️ Attention: When measuring again, be sure to discharge the capacitor by shorting the terminals. If this is not done, the residual charge may damage the internal circuitry of the multimeter, especially if it is switched to current or voltage measurement mode.
If your multimeter does not have a capacitance measurement function, you can use the indirect method. Connect the capacitor in series with an incandescent lamp (for example, 40-60 W) to a 220V network. The lamp should light up at full intensity and burn with an even light. If the lamp burns at full strength, there is a breakdown. If it doesn’t light up at all, it’s a break. But remember: working with mains voltage deadly dangerous without proper qualifications.
Measuring capacitance: accurate diagnostics
The most reliable result is obtained by measuring the actual capacity and comparing it with the nominal value indicated on the case. The main parameters are marked on each capacitor: voltage (for example, 450V) and capacitance (for example, 30 µF). The permissible spread of parameters is usually ±5% or ±10% of the nominal value.
To carry out the measurement, switch the multimeter to the mode Cx. Insert the capacitor leads into the tester sockets or touch them with probes. The screen should display a value in microfarads. If the device shows a value significantly different from the nominal value (for example, instead of 30 μF it shows 12 μF), the part is considered faulty.
The following is a table of typical capacity values for various compressor capacities, which are often found in household refrigerators:
| Compressor power (W) | Refrigerator type | Nominal capacity (uF) | Tolerable deviation |
|---|---|---|---|
| 100 - 150 | Small (single-chamber) | 10 - 16 | ± 10% |
| 180 - 250 | Medium (double-chamber) | 20 - 25 | ± 10% |
| 300 - 400 | Large (No Frost) | 30 - 40 | ± 5-10% |
| 450+ | Industrial / Side-by-Side | 45 - 60 | ± 5% |
It is important to understand that capacity can drop gradually. If you measured 22 µF instead of 25 µF, the refrigerator may work, but the start-up will be difficult, with overheating of the windings. In the long term, it is better to replace such a capacitor. A drop in capacitance of more than 20% of the nominal value is considered critical - in this case, starting the compressor is impossible without the risk of burning out the windings.
Typical errors in diagnostics and replacement
When repairing themselves, beginners often make mistakes that can lead to to repeated failure or damage to the new part. One of the most common is ignoring operating voltage. If you replace the capacitor with 250V instead of 450V, it will quickly swell and fail due to dielectric breakdown.
Polarity is also often confused, although in starting capacitors for refrigerators it is usually not important (they are non-polar), unlike electrolytic ones in control boards. However, if you are installing a universal analogue, it is better to focus on the markings or diagram. Another mistake is using a capacitor with a much larger capacity “in reserve.” This will lead to overheating of the starting winding of the motor.
- ❌ Installing a capacitor with a lower operating voltage (risk of explosion).
- ❌ Using a part with a capacitance higher than 20% of the nominal (risk of motor burning).
- ❌ Poor contact of the terminals (causes sparking and heating).
- ❌ Ignoring checking the starting relay (it could burn out at the same time).
Do not forget that the capacitor is only part of the starting circuit. Often, along with it, the starting relay also fails, which supplies voltage to this capacitor only at the moment of start. If you replace the capacitor but leave a stuck relay, the new element won't last long either.
⚠️ Attention: Compressor specifications and starting hardware requirements may vary between different manufacturers (Atlant, Indesit, Bosch). Always check the parameters of the new part with the markings on the old capacitor or the instructions for your refrigerator model.
Selecting an analogue and completing the repair
If diagnostics confirm a malfunction, you must purchase a replacement. The ideal option is to find an original spare part by catalog number. However, if this is not possible, you can use universal starting capacitors. The main rule: the voltage should be equal or greater, and the capacitance should be as close as possible to the original.
When installing a new part, make sure that the wires are connected securely. Use terminal blocks or high-quality soldering followed by heat shrink insulation. You cannot simply twist the wires - in conditions of vibration of the compressor, the contact will quickly be broken, which will lead to sparking and a fire hazard.
Where to buy a capacitor?
It is better to look in specialized stores of spare parts for household appliances or on radio markets. In general electronics stores, the selection may be limited. Pay attention to the production date - do not take stale goods, even if they are new in the packaging.
After installation, assemble the compressor casing, turn on the refrigerator and listen. Startup should be smooth, without buzzing or clicking. The compressor should pick up speed in 1-2 seconds. If everything went well, you have saved a significant amount on repairs. If the problem is not solved, the compressor itself or the control unit may be faulty, which requires deeper diagnostics.
Is it possible to use a larger capacitor?
Use A capacitor with a capacitance significantly higher than the nominal value (more than +20%) is not recommended. This will increase the starting current, which will cause the motor starting winding to overheat and may shorten the life of the compressor. It is better to put a little less (within -10%) than more.
Why did the new capacitor immediately burn out?
There may be several reasons: the operating voltage was incorrectly selected (too low), the starting relay is faulty (supplies voltage constantly, and not just at the start), or a power surge in the network. It is also possible that the compressor itself has an interturn short circuit.
How long can a capacitor be stored without operation?
Electrolytic capacitors tend to degrade over time even without use. The shelf life is usually 2-3 years from the date of issue. After this, the electrolyte may dry out and the capacity will fall. Always check the production date when purchasing.
Is it dangerous to test a capacitor under voltage?
Yes, it is deadly. Testing with a multimeter is carried out only on a disconnected and discharged element. Testing using the “light bulb method” under a voltage of 220V requires extreme caution and skills in working with electricity.