How to Test Your Car Ignition Coil for Proper Functioning

by:Haiyan     2023-08-31

How to Test Your Car Ignition Coil for Proper Functioning


The ignition coil is an essential component of your car's ignition system. It plays a crucial role in providing the necessary voltage to ignite the fuel in the combustion chamber. Regularly testing the ignition coil can help you identify any issues that may affect engine performance and fuel efficiency. In this article, we will guide you through the steps to test your car's ignition coil for proper functioning.

1. Understanding the Basics of an Ignition Coil:

Before we dive into the testing process, let's first understand the basics of how an ignition coil works. The ignition coil is responsible for converting the low voltage from the battery into a high voltage required to create an electric spark in the spark plugs. This spark ignites the fuel and starts the engine. A typical ignition coil consists of primary and secondary windings, a core, and various electrical connections.

2. Safety Precautions:

Before you begin the testing process, it is crucial to ensure your safety. Here are a few safety precautions to follow:

- Park your car in a well-ventilated area away from any flammable objects.

- Let the engine cool down before attempting to test the ignition coil.

- Wear appropriate protective gear, such as safety glasses and gloves, to prevent any injuries.

3. Gather the Required Tools and Equipment:

To conduct the test accurately, you will need the following tools and equipment:

- Digital multimeter (with resistance and voltage measuring capabilities)

- Screwdriver

- Electrical tape

4. Locating the Ignition Coil:

The ignition coil is usually located near the engine, mounted on the engine block, or attached to the firewall of the car. Refer to your car's service manual to find the exact location of the ignition coil. In most cases, it is a cylindrical-shaped component with several wire connectors.

5. Disconnecting the Ignition Coil:

To test the ignition coil, you need to disconnect it from the rest of the electrical system. Follow these steps to disconnect the ignition coil:

- Start by disconnecting the negative terminal of the car battery to prevent any electrical shock.

- Locate the wire connectors attached to the ignition coil.

- Gently disconnect the connectors by removing the retaining clips or screws.

6. Testing Primary Winding Resistance:

The primary winding of the ignition coil carries the low voltage from the battery. Measuring its resistance can help determine if it is within specifications. Here's how you can test the primary winding:

- Set your digital multimeter to the resistance (ohms) mode.

- Connect the multimeter's probes to the positive and negative terminals of the primary winding.

- Note down the resistance reading displayed on the multimeter. Refer to your car's service manual or manufacturer specifications for the acceptable resistance range.

7. Testing Secondary Winding Resistance:

The secondary winding of the ignition coil produces the high voltage required for the spark plugs. Similar to the primary winding, measuring its resistance is crucial. Follow these steps to test the secondary winding:

- Set your multimeter to the resistance mode.

- Connect one probe to the ignition coil's positive terminal and the other probe to the spark plug wire terminal.

- Note down the resistance reading displayed on the multimeter. Again, refer to the service manual for the acceptable resistance range.

8. Testing for Voltage Output:

Now that you have tested the resistance of both windings, it's time to check the ignition coil's voltage output. Here's how you can do it:

- Set your multimeter to the voltage mode.

- Connect the positive probe to the positive terminal of the ignition coil and the negative probe to a suitable grounding point.

- Ask a friend to crank the engine while you observe the voltage displayed on the multimeter. Compare the reading with the manufacturer's specifications.

9. Inspecting for Physical Damage:

Apart from electrical tests, it is essential to visually inspect the ignition coil for any physical damage. Look out for cracks, corrosion, or any signs of overheating. If you notice any such issues, consider replacing the ignition coil.

10. Reconnecting the Ignition Coil:

After completing the testing process, it's time to reconnect the ignition coil to the electrical system. Follow these steps:

- Reattach the wire connectors to their respective terminals.

- Secure the connectors using retaining clips or screws.

- Reconnect the negative terminal of the car battery.


Regularly testing your car's ignition coil is crucial for maintaining optimal engine performance. By following the steps mentioned in this article, you can ensure that your ignition coil is functioning properly. If you notice any abnormalities in the test results, it is advisable to consult a professional mechanic for further diagnosis and repairs. Remember, a well-maintained ignition coil is essential for a smooth-running engine and improved fuel efficiency.

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