How To Test A/C Capacitor

When it comes to air conditioning systems, the capacitor plays a crucial role in ensuring the proper functioning of the unit. A/C capacitors are responsible for starting and running the compressor and fan motor. If your A/C unit is not working efficiently, one possible reason could be a faulty capacitor. In this article, we will guide you on how to test A/C capacitor and troubleshoot any issues that may arise.

What is an A/C Capacitor?

Before we dive into the testing process, it’s important to understand what an A/C capacitor is. Simply put, a capacitor is an electrical component that stores energy. In an air conditioning system, there are two types of capacitors: the start capacitor and the run capacitor. The start capacitor provides the extra voltage needed to start the compressor, while the run capacitor provides a continuous supply of energy to keep the compressor and fan motor running.

Why Test an A/C Capacitor?

Testing your A/C capacitor is important for a number of reasons. A faulty capacitor can cause your A/C unit to run inefficiently or even stop working altogether. By testing your capacitor, you can identify and troubleshoot any issues before they become major problems. Additionally, testing your capacitor can save you money in the long run by preventing costly repairs or replacements.

How to Test A/C Capacitor: Step-by-Step Guide

Now that you understand the importance of testing your A/C capacitor, let’s walk through the step-by-step process.

Step 1: Turn off Power to the A/C Unit

Before you begin testing your A/C capacitor, it’s important to turn off the power to the unit. This will ensure your safety and prevent any damage to the system.

Step 2: Locate the Capacitor

Next, locate the capacitor in your A/C unit. The capacitor will typically be a small cylindrical or oval-shaped component with two or three terminals.

Step 3: Discharge the Capacitor

Before testing the capacitor, it’s important to discharge any residual energy. This can be done by using an insulated screwdriver or a capacitor discharge tool.

Step 4: Test for Continuity

To test for continuity, use a multimeter set to the ohms setting. Touch the multimeter leads to the terminals on the capacitor. If the multimeter reads a low resistance, the capacitor has continuity and is functioning properly.

Step 5: Test for Capacitance

To test for capacitance, use a multimeter set to the capacitance setting. Touch the multimeter leads to the terminals on the capacitor. The multimeter should display a reading that matches the capacitance rating of the capacitor. If the reading is significantly lower, the capacitor is faulty and needs to be replaced.

Step 6: Reinstall the Capacitor

If the capacitor tests positive for continuity and capacitance, you can reinstall it into the A/C unit. Make sure to connect the terminals correctly.

FAQs About How to Test A/C Capacitor

Q: Can I test an A/C capacitor without a multimeter?

A: No, a multimeter is required to test A/C capacitors.

Q: What happens if I don’t test my A/C capacitor?

A: If you don’t test your A/C capacitor, you risk running your A/C unit inefficiently or causing the unit to stop working altogether.

Q: How often should I test my A/C capacitor?

A: It’s recommended to test your A/C capacitor every year to ensure proper functioning.


Testing your A/C capacitor is an important part of maintaining your air conditioning system. By following these steps and testing your capacitor regularly, you can ensure that your A/C unit runs efficiently and avoid costly repairs or replacements. Remember to always turn off the power to the unit before testing and to use a multimeter for accurate readings.