How To Test Ac Capacitor With Digital Multimeter

AC capacitors are an essential component of any air conditioning system. They store and release electrical energy to keep the compressor running smoothly. However, over time, these capacitors can weaken or fail altogether, causing your AC unit to malfunction. That’s why it’s crucial to know how to test AC capacitor with a digital multimeter. In this blog post, we’ll guide you through the process step by step.

What You’ll Need to Test AC Capacitor with Digital Multimeter

Before we get started, you’ll need a few things:

  • Digital Multimeter
  • Safety Gloves and Goggles
  • Insulated Screwdriver
  • Replacement Capacitor (Optional)

Step 1: Turn Off the Power

The first step is to turn off the power to your AC unit. This is important for your safety and to prevent any damage to the system. Make sure to disconnect the power supply entirely before proceeding.

Step 2: Discharge the Capacitor

The next step is to discharge the AC capacitor. You can do this by using an insulated screwdriver to short-circuit the capacitor’s terminals. Make sure to wear safety gloves and goggles while doing this.

Step 3: Set Your Multimeter to Ohms

Now, set your digital multimeter to the ohms setting. This will help you measure the resistance of the capacitor.

Step 4: Test the Capacitor

With your multimeter set to ohms, touch the leads to the capacitor’s terminals. You should see the reading on the multimeter’s display. If the reading is zero or close to zero, the capacitor is shorted and needs to be replaced. If the reading is infinity or higher than the capacitor’s rated value, the capacitor is open, and again, it needs to be replaced.

Step 5: Check Capacitor’s Rating

If the capacitor’s resistance is within the allowable range, check its rating by reading the label on the capacitor. Make sure the reading on the multimeter is close to the capacitor’s value. If there’s a significant difference, the capacitor is faulty and needs to be replaced.

Step 6: Test Capacitor’s Voltage

You can also test the capacitor’s voltage by setting your multimeter to the voltage setting. Touch the leads to the capacitor’s terminals and check the reading. If the reading is lower than the capacitor’s rated voltage, it’s a sign that the capacitor is weak and needs to be replaced.

Step 7: Reconnect the Capacitor

If the capacitor passes all tests, reconnect it to the AC unit. Make sure to reattach the wires correctly to avoid any further complications.

Step 8: Turn the Power Back On

Finally, turn the power back on and test your AC unit to make sure it’s working correctly. If your AC unit still has problems, you may want to consult a professional technician.


Q: What causes an AC capacitor to fail?

There are several reasons why an AC capacitor can fail, including overheating, voltage spikes, and age.

Q: Can I test an AC capacitor without a multimeter?

No, you can’t test an AC capacitor without a multimeter. A multimeter is the only tool that can accurately measure a capacitor’s resistance and voltage.

Q: Can I replace an AC capacitor myself?

Yes, you can replace an AC capacitor yourself if you have the necessary tools and knowledge. However, if you’re not confident in your abilities, it’s best to hire a professional technician.


Testing an AC capacitor with a digital multimeter is a simple process that can save you time and money. By following the steps outlined in this blog post, you can quickly determine whether your AC capacitor is working correctly or not. Remember to always wear safety gloves and goggles when working with electrical components and turn off the power supply before beginning any repairs. If you’re unsure about anything, don’t hesitate to seek professional help.