How To Test A Capacitor With A Multimeter?

Energy is stored in capacitors in the form of electric charges. Capacitors are too important to ignore; they are electrical components that perform significant roles in your electronics. Capacitors carry out the functions of charging and discharging, which is releasing charge into the circuit through a plate of the capacitor when a first charged plate can longer hold current built up in it.

Capacitors are parts of the motors of your air conditioners, heaters, and your refrigerator compressors. So apparently, one of the faults of your electronics could be with your capacitor.

To test your capacitor, you would have to make use of a multimeter (if you don’t have a multimeter check on Amazon.com and pick one). You should know that the multimeter functions as a troubleshooting device that measures resistance, current, and voltage. But the question would be “how do you test a capacitor with a multimeter?” We would answer this question by briefly explaining how you can use multimeters with different functions to test your capacitor.

  • How to Test the Capacitor Using a Multimeter with Capacitance Setting

If you have a digital multimeter that functions with capacitance settings, then feel lucky! It is the quick and accurate way of carrying out this test.

Capacitance is measured in Farads, using a multimeter with capacitance settings, it can measure capacitors as small as a few nanoFarads to bigger microfarad capacitors.

 

  1. To carry out this test, you would have to detach the capacitor from the circuit board and completely discharge it; you can do this by connecting it to a LED or powerful resistor. You may have both your capacitor and voltage rating printed on the exterior your capacitor, so the next thing to do is to take note of these ratings.
  2. Set the knob on your digital multimeter to capacitance settings, then connect the probes to the terminals of the capacitor. To get your readings right on an electrolytic capacitor, connect the red probe to the positive terminal, then the black to the negative terminal. For non-electrolytic, you can join them either way; it wouldn’t matter.
  3. After all these settings and placements, you can now check the readings on your multimeter. Because electrolytic capacitors could dry up, your reading might be a little lesser than the ratings on the exterior, but as long as it is close to the rating, your capacitor is working correctly.

If the difference between your readings and the rating is a significant value, then the problem of your appliance could be a defective capacitor.

  • How to Test the Capacitor Using a Multimeter without Capacitance Settings

As some less expensive multimeters lack the capacitance settings, and if one of these is what you own, you can still conduct tests on your capacitors with them.

  1. Like the multimeters with capacitance setting, you would first have to remove the capacitor from the circuit and ensure it is discharged. The next thing to do here is to set the knob of the multimeter to ohms to measure resistance and select a high range.
  2. Also, like the previous multimeter we spoke about, connect the probes red to positive and black to negative in the case of electrolytic capacitors, and in the case of non-electrolytic, you can place them either way.
  3. The digital multimeter would display a reading of resistance, so note it, before it changes to the resistance of an open circuit which is infinity.
  4. After these, disconnect the probes from the capacitors and repeat the process severally. Each test should show a different reading of resistance to prove that the capacitor is working correctly, so when it displays the same results severally, you have a damaged capacitor.

Testing capacitors using multimeters without capacitance settings can’t assure you of the accuracy of the capacitance of the capacitor, but you can determine if a capacitor is good or bad with it.

  • How to Test the Capacitor Using a Multimeter to Measure Voltage

Multimeters can function as a voltmeter, and capacitors are rated with a maximum voltage that can be applied to them, so this test would be centered on measuring the voltage rating of the capacitor.

To carry out this test, you should also follow the normal process of removing the capacitor from the circuit or board and ensuring it is discharged.

  1. The voltage rating imprinted on your capacitor is the maximum voltage it can handle, so connecting it to a power source with a higher volt rating can cause damage. So note the voltage rating on the exterior of the capacitor, then attach it to a battery or a power supply that is not up to the noted ratings. For example, you can use a battery of 12 Volts on a capacitor of 25 Volts.
  2. Leave the capacitor to charge for some seconds before removing the power supply. Now set your digital multimeter to direct current voltmeter settings, properly connect the terminals of the capacitor to the probes of your multimeter, positive to red and negative to black as need be, then measure the voltage.
  3. Take note of your initial reading on the multimeter, if it is close to the voltage of the battery or power source connected to it, then the capacitor is good, and if there is a significant difference, then the capacitor is faulty.

It is important you know that gradually the voltage falls, so the only reading that should be noted is the first one.

  • How to Test the Capacitor Using Analog Multimeter

Just like the digital multimeter, analog multimeters can also be used to test your current, voltage and resistance. While using this multimeter to test capacitors, you would make use of the Ohms function.

  1. The first thing you do, as usual, detach the capacitor from the board and discharge it, if your analog multimeter has multiple Ohms ranges, put it in an ohmmeter’s position, but choose a high range.
  2. Connect the probes of your multimeter to the leads of the capacitors and observe the readings. Analog multimeters display their readings with the movement of a needle, which would determine if the capacitor is good or bad.

For a working capacitor, the needle would show a low resistance value and would gradually increase as it moves to the right. The capacitor is a shorted capacitor and would need replacement if the needle remains low. If the needle reads a high value on the multimeter, or it does not move at all, then the capacitor is an open circuit, meaning it is dead and must be replaced.


Conclusion

As we conclude, we would like you to know that although capacitors can be classified into electrolytic and non-electrolytic capacitors, they fail for several reasons. The electrolytic capacitors fail from discharging too much current within a short period, while the non-electrolytic capacitor fails due to leakages.

Another reason why any of both classes can be damaged could be from spikes or voltage swings. If a test on your appliance shows you have a defective capacitor, you can have some savings from hiring a technician for repairs or getting a new appliance by replacing your capacitors and getting your appliance back to full function.

FAQ

How to test a capacitor with a multimeter in a circuit?

Before we begin, you should know that testing capacitors with a multimeter in a circuit can be dangerous and should be done by a professional. If you feel that you have enough experience and technical knowledge to do this make sure that you take safety precautions either way and keep on reading. That being said, the process of testing capacitors with multimeters while in a circuit is an easy thing to do.

First of all, you need to take the pliers and discharge the capacitor with them. You can do this by pressing both the positive and negative capacitor leads with the pliers, just make sure that your pliers have rubber handles and don’t press too firmly. Closing the pliers should be enough in most cases. After you finished doing this, take your multimeter and set it t capacitance mode.

If you have an auto-ranging multimeter, that is excellent, if you don’t make sure that you set your multimeter on the highest possible capacitance setting it has. Identify positive and negative leads on the capacitor and press the probes against them. You should get a reading and it should start moving towards infinity.

If you have any trouble with pressing multimeter probes to capacitor leads and maintaining contact, you can replace one or both probes on the multimeter with alligator probes. Just make sure that you have enough room on the capacitor leads to placing them on.

How to discharge a capacitor with a multimeter?

Once again, this too can be extremely dangerous, especially if you are doing this while the capacitor is in the circuit. If you don’t have to do this by yourself, it would be best to call an electrician. If you decided to proceed, make sure that you take every precaution possible. I love to wear high-current-resistant rubber gloves designed specifically for this purpose.

In order to do this, your multimeter needs to have a low impedance function, and a pair of probes that are covered with thick rubber. Your multimeter should also be at least CAT III certified if you want to attempt to do this with it.

So, here’s the deal.

Set your multimeter on the low impedance function and take the probes. Identify which lead is positive and which one is negative, on the capacitor, and place the probes accordingly. Hold the probes on the poles and wait for the discharge process to complete.

It is not necessary to do anything else besides looking out for your safety, as the multimeter will take care of the process of discharging the capacitor. You can observe the level of charge on the multimeter screen. Depending on a type of the capacitor, a beginning charge value will differ from model to model.

You need to make sure that you keep the probes on the poles until the value on the multimeter reaches zero. It can also pay off to visually inspect the capacitor for damage and puffed up top before you begin. If you find any signs of damage, don’t do this, and contact a professional.

How to test the capacitor on a board?

Capacitors on boards are tested in the same way as we test capacitors when they are not on boards. First, you need to make sure that the board is not connected to any power source while you perform this test. Next, you need to visually inspect the capacitor for damage.

Most prominent sign of damage on the capacitor, that can be detected visually is a puffed up top. If you see this, don’t even bother to test a capacitor because it is definitely damaged. Take a pair of pliers and press them on the leads of the capacitor before you begin the test. This will discharge the capacitor and enable you to get a more accurate reading.

Once you did that, take your multimeter and turn the dial on capacitance mode. Make sure that you check polarities of a capacitor that you are going to test to know which probe to place where. Have in mind that this can be dangerous and make sure that you are one hundred percent sure that you know what are you doing before you proceed.

Take multimeter probes and place them on the capacitor leads according to their poles. You should get a reading. If you aren’t sure what does a reading that you got means, please refer to the main article to get in-depth instructions on how to read capacitance measuring results.

How to test a refrigerator capacitor?

Capacitors used in cooling and heating devices are called ‘start capacitors’. They can be easily identified as they are usually quite larger than common capacitors. I am writing this because you need to remove the capacitor from the fridge in order to test it. 

Before you begin removing the capacitor from the fridge, make sure that the fridge is not plugged in an electrical socket and have in mind that working with such large capacitors can be extremely dangerous as old fridge capacitors can sometimes explode unless the fridge was properly maintained. Inspect the side of your capacitor for more detail and adjust the settings on your multimeter accordingly.

Usually, setting your multimeter on the highest capacitance settings works best, but don’t take my word for granted. I don’t recommend that you attempt to discharge fridge capacitors by yourself if you don’t know what are you doing, besides, some fridge capacitors can get damaged irreversibly if you do it the wrong way, while others might blow up your multimeter if you don’t discharge them.

It’s best to google the capacitor and see for yourself on the site of its manufacturer or call in a professional. Once you got this settled, take your multimeter and place the probes on the correct terminals on the capacitor, after you have identified them correctly, of course.

How to test an air conditioner capacitor with a multimeter?

Air conditioner capacitors can be as large as refrigerator capacitors, or even bigger! The good news is that you don’t need any special equipment to test them and make sure that they are operational – a multimeter will be enough. First of all, you need to remove the capacitor from your AC unit. The process of removing capacitors from air conditioning units differs from model to model.

You don’t need to remove capacitors on some models, but they are very rare. Since this could be dangerous if you aren’t sure what are you doing, contact an AC technician to do this for you. Unlike ordinary capacitors, AC capacitors have three terminals. Identify ‘C’ and ‘fan’ terminals on the capacitor. Set your multimeter to capacitance.

Place the positive probe on the ‘C’ terminal and the negative probe on the ‘fan’ terminal. If your capacitor is operational, the value on the multimeter display should increase. If there is no increase in value, the capacitor is damaged.

How to test a start capacitor with a digital multimeter?

A start capacitor is a capacitor that alters the current output so that the motor can start turning. Hence the name ‘start’ capacitor. Generally, start capacitors don’t differ a lot from other types of capacitors. They can be somewhat larger in size, but that just makes them easier to identify and remove if needed. I prefer using alligator probes to discharge this type of capacitor.

Take your capacitor and take two gator probes. Identify the positive and negative terminals on the capacitor and clamp them accordingly with your gator probes. Make sure that the probes aren’t plugged in a multimeter when you do this part. Also, you need to be extra careful not to touch the ends of the Gators when doing this and prepare for a spark. 

Now take the ends and connect them together for a fraction of a second. Repeat if necessary. Once again, be extra careful to keep your fingers at a distance while doing this and if you are not sure what you should do, call in a professional. Once the capacitor is discharged set your multimeter on capacitance mode and plug the Gators in. If there’s no reading or if it stays the same at a pretty low level, you know that your start capacitor is damaged.

How to test a motor capacitor with a multimeter?

Place the capacitor on the table or any other flat surface. Take your multimeter and set it to capacitance. After you did that, you need to visually inspect the capacitor for damage. Since they are pretty big and sturdy, it is unlikely that they will get physically damaged, but nevertheless, do it.

If you detect any signs of physical damage ( by physical damage I mean ruptures and heavy swelling) don’t test the capacitor, instead get a new one. Electrical motor capacitors have two terminals, so make sure that you identify the positive and negative one before we begin.

Place the positive lead on the positive terminal and the negative lead on the negative terminal and hold them there. As you do this, you should see an increase in the value that is displayed on your multimeter. The value will reach a certain point and then start dropping down. This happens because the capacitor soaks up the power when it reaches a certain point, as it should. If the value remains static, this means that the capacitor is broken.

How to test a microwave capacitor with a multimeter?

After you remove a capacitor from the microwave, make sure that you discharge them entirely. You can use the method that involves the pliers, or you can use your multimeter. What’s important is that the capacitor is fully discharged before you begin the test.

After you place the capacitor on the side identify the positive and negative terminals. It would be best if you would use alligator clips and clip the terminal accordingly. Take another pair of alligator clips and clip the remaining terminals together to keep the charge flowing naturally. You probably know how to do the next part.

Take your multimeter and set it to capacitance. Plug the positive and negative gator probes in your multimeter and check the reading. If your capacitor is in working order, the reading should start rising and after it reaches a certain point it should start falling because the capacitor has begun to absorb the energy from the multimeter.

How to test a heat pump capacitor with a multimeter?

Capacitors from a heat pump can have two or three terminals. The process for a two-terminal capacitor remains the same as with any other type of capacitor. Identify the polarity of each terminal and discharge them, either using gator clips or the plier method. Be careful while doing this because there will be residual electrical energy discharged while you do this. Once the capacitor is discharged, take your multimeter and connect the terminals according to their polarity.

Read the results, and that’s it.

In order to test a heat pump capacitor with three terminals, you first need to identify on which terminal is the positive and which one the negative one. Also, each terminal serves a specific function, i.e. connects to another integral part and enables it to work properly. Make sure that you know the layout of your multimeter before you do this.

Discharge the positive and negative terminals and set your multimeter on the capacitance mode. Connect the probes and check out the reading. If you did everything correctly, the remaining terminal should also be positive (depends from the capacitor to capacitor) so you can test that terminal too.

How to test a capacitor with a multimeter on a motherboard?

Make sure that the motherboard isn’t connected to any power source before you begin doing this. The most important thing to look out for if you want to test a capacitor with a multimeter that is still connected to the motherboard is the space. Do you have enough space to fit the probe tips to touch the polarities of the capacitor? It doesn’t have to be on the top side of the motherboard. Some capacitors are soldered to a motherboard in such a way that their terminals stick out on the other side of the motherboard. Check to see if this is the case.

If possible, take the pliers with handles that are engulfed in rubber and discharge the capacitor with them. If this is not possible, take the probes of your multimeter and discharge the capacitor using them. Make sure that the gator probes are disconnected and that you don’t hold them for any part that might conduct electricity or where a spark could reach you.

Connect the probes according to each capacitor pole and press the ends of the wires together for a moment. Have your fingers at a distance from the part that you will connect so that you don’t get shocked. Press them together for a moment and remove them immediately as soon as the spark has passed. Take your multimeter and set it to capacitance. Connect the probes to the terminals according to their polarity and check the results.

How to test a blower motor capacitor with the multimeter?

If you want to test a blower motor capacitor of yours, make sure that you discharge it with a screwdriver before you begin the test. Press the screwdriver against the terminals and the capacitor will discharge. Make sure that your screwdriver has a handle that is resistant to electric shock and is careful once you start to discharge the capacitor. Blower motor capacitors usually have two terminals, but also many of them have three terminals.

The process is basically the same for both types, with the only difference being that capacitors that have three terminals have two positive terminals instead of one, like on the capacitors that have two terminals. Once the capacitor is discharged, take your multimeter and set it to capacitance. Identify the positive and negative terminals and place the probes on them. Check your multimeter for a reading.

How to test a pool pump capacitor with a digital multimeter?

If you believe that there is a problem with your pool pump capacitor and you want to test it to make sure, go to the panel that controls the work of the pool. Set it in off position and make sure that the section of the pool that controls the water flow is without electric energy. Set all breakers in the off position. If you aren’t sure that you have correctly and safely disconnected your pool from the electric grid call in a professional to do this instead. You should do this as further away from water as possible. Open a case that covers the capacitor and disconnects the capacitor from the grid. Leave the capacitor where it is and get a pair of alligator clips.

Before you begin to discharge the capacitor, you should know that there is a serious danger of injury or death when it comes to the capacitor of this size. Once again, if you aren’t sure what are you doing, call in a professional. Connect the two terminals with alligator clips carefully. Take a pair of long shock resistant pliers and shake the terminals with them slightly. The capacitor should discharge itself.

Next, take your multimeter and set it to capacitance.

Disconnect the gator clips from the capacitor and identify the positive and negative terminals. Connect the probes accordingly. Check the reading you got. If the value is static, the capacitor is probably broken. Since this is a very large capacitor, make sure to set your multimeter on a highest setting possible in order to detect higher levels of charge.

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