Capacitors are electrical charge storage devices used in electronic circuits, such as those in fan motors and air conditioning compressors in your home. There are 2 types of capacitors: electrolytic, which is used in vacuum cleaner tubes and transistor power lines, and nonelectrolyte, which is used to regulate direct current surges. Electrolytic capacitors can be damaged because they get too high a current flow or run out of electrolyte so they can't withstand the incoming current. Meanwhile, nonelectrolyte capacitors are often damaged due to power leakage. There are several ways to test if a capacitor is still working properly.
Step
Method 1 of 5: Using a Digital Multimeter With Capacity Settings
Step 1. Remove the capacitor from the circuit if it is still connected
Step 2. Read the capacitance value on the outside of the capacitor
The unit of capacity used is farad. This unit has a capital letter “F” symbol. You may also see the Greek alphabet (µ) which looks like a small “u” with a tail at the front. (Since the farad is a large unit, most capacitors measure capacitance in microfarads; one microfarad is equal to one millionth of a farad.)
Step 3. Set the multimeter to the capacity setting
Step 4. Connect the tip of the multimeter to the terminals of the capacitor
Connect the positive (red) wire on the multimeter to the anode head of the capacitor and the negative (black) wire to the cathode head of the capacitor. (In most capacitors, especially electrolytic capacitors, the anode head is usually longer than the cathode head.)
Step 5. Check the reading on the multimeter
If the capacity reading on the multimeter is almost the same as the value listed on the capacitor unit, the condition is still good. If the reading is much lower than the value on the capacitor unit, or zero, the capacitor is dead.
Method 2 of 5: Using a Digital Multimeter without Capacity Setting
Step 1. Disconnect the capacitor from its circuit
Step 2. Set the multimeter to the resistance setting
This setting is usually indicated by the words “OHM” (unit of power resistance) or the Greek alphabet omega omega (Ω which stands for ohm.
If the resistance range setting on your multimeter can be changed, set it to 1000 ohms = 1K or higher
Step 3. Connect the tip of the multimeter to the terminals of the capacitor
Again, connect the red lead to the positive (longer) terminal and connect the black lead to the negative (shorter) terminal.
Step 4. Pay attention to the readings of the multimeter
Record the initial resistance value, if desired. The value will return to its original value as before you connected the terminal end.
Step 5. Disconnect and reconnect the capacitor several times
You should get the same result as the first test. If true, the condition of the capacitor can be ascertained is still good.
However, if the resistance value does not change, the capacitor is dead
Method 3 of 5: Using an Analog Multimeter
Step 1. Disconnect the capacitor from its circuit
Step 2. Install the resistance setting on the multimeter
As with digital multimeters, these settings are usually marked with the words “OHM” or omega (Ω).
Step 3. Connect the tip of the multimeter to the terminals of the capacitor
Connect the red lead to the positive (longer) terminal and the black lead to the negative (shorter) terminal.
Step 4. Pay attention to the measurement results
Analog multimeters use needles to display the readings. The movement of the needle will indicate whether or not the condition of the capacitor is good.
- If the needle shows a low resistance value, then gradually moves to a larger number without stopping, the condition of the capacitor is still good.
- If the needle shows a low resistance value and doesn't move, the capacitor is faulty and you need to replace it.
- If the needle shows no resistance value at all or shows a large resistance value without moving an inch, the capacitor is dead.
Method 4 of 5: Testing a Capacitor with a Voltmeter
Step 1. Disconnect the capacitor from its circuit
If you wish, you can remove one of the two connections attached to the circuit.
Step 2. Check the voltage rating of the capacitor
This information is usually printed on the outside of the capacitor. Look for a number followed by a large “V” or a “volt” symbol.
Step 3. Charge the capacitor with a lower voltage, but close to the original voltage
For a capacitor with a capacity of 25V, you can use a power of 9 volts, while for a capacitor with a capacity of 600V, you need to use a minimum power of 400 volts. Let the capacitor charge for a few seconds. Make sure you connect the positive (red) terminal of the power source to the positive (longer) capacitor and the negative (black) terminal of the negative (shorter) capacitor.
The bigger the difference between the capacitor's voltage rating and the voltage you're using, the longer it will take to charge. In general, a high voltage at the power source used will make it easier for you to test the voltage rating on large capacity capacitors
Step 4. Set the voltmeter to read DC voltage (if it is capable of reading both AC and DC voltages)
Step 5. Connect the voltmeter lead to the capacitor
Connect the positive (red) terminal to the positive (longer) terminal and the negative (black) terminal to the shorter (shorter) terminal.
Step 6. Record the initial voltage reading
The result should be close to the amount of voltage you use to supply power to the capacitor. Otherwise, the capacitor is faulty.
The capacitor will discharge voltage into the voltmeter so that the reading will return to zero after some time. This is normal. You only need to worry if the readings turn out to be much lower than the amount of voltage you are using
Method 5 of 5: Electrocuting Capacitor Terminals to Generate Sparks
Step 1. Disconnect the capacitor from its circuit
Step 2. Connect the terminal end to the capacitor
Again, connect the positive (red) pole to the positive (longer size) terminal and the negative (black) terminal to the negative terminal.
Step 3. Connect the other end of the power cord in no time
You should not leave it plugged in for more than 1 to 4 seconds.
Step 4. Disconnect the terminal end from the power source
This is done to prevent damage to the capacitor while you are making repairs and reduce the risk of electric shock.
Step 5. Stun the capacitor terminals
Make sure you wear insulating gloves and don't touch the metal directly with your hands while doing this.
Step 6. Watch for sparks when you shock the terminal
The intensity of the spark can indicate the capacity of the capacitor.
- This method only works for capacitors that are able to withstand the energy to produce sparks when electrocuted.
- This method is not recommended because it is only useful for determining the capacitor's ability to absorb power and generate sparks when electrocuted. This method cannot be used to test whether the power capacity in the capacitor is still within its initial specifications.
- Using this method on large capacitors can cause serious injury or even death!
Tips
- Nonelectrolyte capacitors are usually not polarized. When testing this type of capacitor, you can connect the lead of a voltmeter, multimeter, or other generating device to any of the terminals of the capacitor.
- Nonelectrolyte capacitors are divided into several types based on their base material – ceramic, mica, paper, or plastic – and plastic capacitors are further divided into several types according to the type of plastic.
- Capacitors used for heating and air conditioning systems in terms of function are divided into two types. Run type capacitors are used to maintain voltage flow from fan motors and compressors in burners, air conditioners, and heating pumps. Meanwhile, starting capacitors are used in high torque motors in heating and air conditioning pumps to provide extra energy when turned on.
- Electrolytic capacitors usually have a tolerance of 20%. In other words, a still good capacitor may have a capacity 20% greater or less than its normal capacity.
- Make sure you don't touch the capacitor that is being charged as doing so could electrocute you.
