How To Check A Ac Capacitor With A Multimeter

5 min read Jun 26, 2024
How To Check A Ac Capacitor With A Multimeter

How to Check an AC Capacitor with a Multimeter


An AC capacitor is a crucial component in many electrical circuits, including air conditioners, refrigerators, and other appliances. However, like any other component, it can fail or become damaged, leading to system failure or inefficiency. In this article, we will guide you on how to check an AC capacitor with a multimeter, a simple and essential tool for any DIY enthusiast or electrician.

Understanding Capacitor Ratings

Before we dive into the checking process, it's essential to understand the capacitor ratings. A typical AC capacitor has the following ratings:

  • Voltage Rating: The maximum voltage that the capacitor can handle.
  • Capacitance: The amount of electrical energy the capacitor can store, measured in microfarads (μF).
  • Frequency: The AC frequency the capacitor is designed to operate at, typically 50Hz or 60Hz.


To check an AC capacitor with a multimeter, you'll need:

  • A multimeter (digital or analog)
  • The capacitor to be tested
  • A non-conductive surface to work on

Step-by-Step Procedure

1. Safety First

Ensure you're working in a safe environment, away from any electrical sources. Remove any power sources from the capacitor before testing.

2. Visual Inspection

Inspect the capacitor for any signs of physical damage, such as cracks, rust, or burn marks. Check the terminals for corrosion or loose connections.

3. Set the Multimeter

Set your multimeter to the capacitance (C) or microfarad (μF) function. The capacitance range will depend on the type of multimeter you have, but typical ranges include: * 200nF to 200μF * 20μF to 2000μF * 200μF to 20,000μF

4. Connect the Multimeter

Connect the multimeter leads to the capacitor terminals. The red lead usually connects to the positive terminal, and the black lead connects to the negative terminal. Ensure the leads are securely connected to prevent any false readings.

5. Take the Reading

Take the capacitance reading on your multimeter. Compare the reading to the capacitor's rated capacitance value. A good capacitor should read close to its rated value.

6. Check for Leakage

Switch the multimeter to the ohms (Ω) function. Measure the resistance between the capacitor terminals. A good capacitor should read infinite ohms or a very high resistance. Any reading below 1MΩ indicates a leaky capacitor.

7. Check for Short Circuit

Set the multimeter to the diode test function. Measure the forward voltage drop between the capacitor terminals. A good capacitor should read around 0.5 to 1.5 volts. Any reading close to 0 volts indicates a short-circuited capacitor.


Checking an AC capacitor with a multimeter is a straightforward process that can help you identify faulty or damaged capacitors. By following these steps, you can ensure your electrical circuits operate efficiently and safely. Remember to always exercise caution when working with electrical components, and consult a professional if you're unsure about the testing process.

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