How to Test an Ignition Coil at Home: A Comprehensive Guide

Ignition coils are a critical part of your car's engine that helps to ignite the air-fuel mixture in the combustion chamber. Over time, they can wear out, leading to various engine issues. Fortunately, you can test your ignition coil at home with a few simple steps. This guide will walk you through the process and help you determine if your ignition coil is faulty.

Testing Methods and Tools Required

To test an ignition coil, you will need a Volt-Ohm Meter Multimeter. This device is essential for measuring resistance, voltage, and current. Additionally, it is important to have manufacturer-specific specifications for the ignition coil you are testing, as these will provide you with the correct resistance values for comparison.

Testing an Ignition Coil Using a Multimeter

Begin by disconnecting the battery negative lead (usually marked as -).

Remove the high tension lead (usually a thick wire) from the ignition coil.

Set your multimeter to the ON position and adjust the knob to the 20K Ohm position.

Place the red probe of the multimeter on the central terminal of the ignition coil and the black probe on the negative terminal marked as -. The meter should read between 6k to 16k Ohms. A reading outside of this range indicates a faulty secondary winding.

Next, switch the multimeter to the 200 Ohms scale to test the primary winding. Place the red probe on the small terminal of the coil and the black probe on the negative terminal. The reading should be around 0.3 to 4.0 Ohms. A different reading suggests a problem with the primary winding.

Testing Ignition Coils on Individual Cylinders

For newer vehicles with individual ignition coils on each cylinder, the testing process is slightly different. Follow these steps:

Remove the ignition coil and the plug boot.

Place the end of the high tension lead (thick wire) near a good ground on the engine, ensuring the wiring connector is properly attached.

Crank the engine and observe for a strong spark. The absence of a spark indicates a problem with the coil or the wiring.

Additional Testing Methods

Testing on Engine Misfire

If you suspect a misfire, you can use a more practical method:

If your engine has individual coils per cylinder, trade coils with another cylinder to see if the problem shifts.

For vintage cars with individual coils, pull the spark plug and lay the metal part where it usually goes on a grounded metal part of the engine. Make sure to disable the fuel pump by removing the fuse so the engine doesn't crank. Turn the key and look for a blue spark.

Steps to Test an Ignition Coil at Home

Ensure the battery negative lead is disconnected.

Take out the high tension lead from the ignition coil.

Adjust the multimeter to 20K Ohm and measure the resistance of the secondary winding. A reading within the range of 6k to 16k Ohms is normal.

Switch the multimeter to 200 Ohms to test the primary winding. A reading between 0.3 to 4.0 Ohms indicates a healthy coil.

Conclusion

Testing an ignition coil at home is a straightforward process that can save you time and money in the long run. By following these guidelines, you can identify if your ignition coil is faulty and take action to preserve the performance of your vehicle. Remember to always prioritize safety and consult the manufacturer's specifications for accurate testing values.