How To Check Ac Capacitor Using Multimeter

6 min read Jun 26, 2024
How To Check Ac Capacitor Using Multimeter

How to Check an AC Capacitor Using a Multimeter

An AC capacitor is a crucial component in many electronic devices, including air conditioners, refrigerators, and pumps. It helps to improve the power factor, reduce energy losses, and increase the efficiency of the device. However, like any other component, an AC capacitor can fail or become weak over time, affecting the performance of the device. In this article, we will discuss how to check an AC capacitor using a multimeter.

Why Check an AC Capacitor?

Checking an AC capacitor is essential to ensure that it is functioning properly and to identify any potential issues before they cause damage to the device. Here are some reasons why you should check an AC capacitor:

  • Improved Performance: A faulty capacitor can reduce the efficiency of the device, leading to increased energy bills and decreased performance.
  • Prevent Damage: A failed capacitor can cause damage to other components in the device, leading to costly repairs or even complete device failure.
  • Increased Safety: A faulty capacitor can also pose a safety risk, as it can cause electrical shocks or even fires.

Tools Required

To check an AC capacitor, you will need the following tools:

  • Multimeter: A digital multimeter is the most common tool used to measure the capacitance, voltage, and current of the capacitor.
  • Capacitor Tester: Some multimeters come with a built-in capacitor tester, which can simplify the testing process.

Step-by-Step Guide to Checking an AC Capacitor

Step 1: Disconnect Power

Before starting the test, ensure that the power to the device is disconnected to prevent any accidentalstart-up or electrical shock.

Step 2: Identify the Capacitor

Identify the AC capacitor in the device and its specifications, including the capacitance value, voltage rating, and terminal type (e.g., axial or radial).

Step 3: Set the Multimeter

Set the multimeter to the capacitance measurement mode (usually denoted by the symbol "C" or "FARAD"). Ensure that the multimeter is set to the correct range for the capacitor's capacitance value.

Step 4: Connect the Multimeter

Connect the multimeter leads to the capacitor terminals, ensuring that the leads are securely connected to prevent any accidentaldisconnection.

Step 5: Take Readings

Take readings of the capacitor's capacitance value and compare it with the specified value. A reading close to the specified value indicates that the capacitor is functioning properly.

Step 6: Check for Leakage

Check for any signs of leakage or short circuits in the capacitor using the multimeter's ohmmeter function. A good capacitor should have a high resistance reading (usually in the range of megaohms).

Step 7: Check the Voltage Rating

Check the capacitor's voltage rating using the multimeter's voltage measurement function. The reading should be close to the specified voltage rating.

Interpreting the Results

  • Good Capacitor: A reading close to the specified capacitance value, no signs of leakage, and a voltage reading close to the specified rating indicate that the capacitor is functioning properly.
  • Weak or Leaky Capacitor: A reading significantly lower than the specified capacitance value or signs of leakage indicate that the capacitor is weak or leaky.
  • Failed Capacitor: A reading of zero or a very low capacitance value, or a voltage reading significantly higher than the specified rating, indicate that the capacitor has failed.


Checking an AC capacitor using a multimeter is a relatively simple process that can help you identify potential issues before they cause damage to the device. By following the step-by-step guide outlined in this article, you can ensure that your AC capacitor is functioning properly and efficiently.