In a car, an ignition coil converts the 12 Volts of power from the battery to the thousands of volts that are required to fire the spark plugs. This component is essentially an induction coil or better yet, a high voltage transformer. While ignition coils are basically very sturdy and reliable, over time, because of heat, vibrations, and faulty insulation, they can become bad.
There are just about two ways to test the ignition coil of your car: the spark plug test and the bench test. While the spark plug test is effective, the bench test seems more thorough. Why? In the first, you are depending on the spark to determine the condition of your coil; in fact, only in a no-spark situation would you be certain that your coil is faulty. In the second, you are depending on resistance readings and data to test the condition of the ignition coil. Here, even if there is only slight damage to your coil, your readings will indicate it.
Read on for proper instructions on how to carry out these tests so you can be sure if your coil needs to be changed.
1 – TAKE PRECAUTIONARY STEPS
When testing car parts, particularly the engine, you need to be extremely careful. Before you start, make sure to put on safety goggles, that you are not wearing any loose clothing, and that your hair, if long, is neatly tied back. Also, the engine of a car gives electricity, so you will want to take utmost precaution to prevent any unfortunate electric incidents.
2 – REMOVE THE SPARK PLUG/WINDINGS
For the spark plug test,begin by removing the wire from the plug. It is advisable to refer to your car’s service manual to ensure that you are removing the correct wires. Then, with the help of a spark plug socket, remove the spark plug.
If you’re conducting the bench test, refer to your service manual and remove the two windings (primary and secondary) that are inside your ignition coil.
3 – CONFIRM IF THERE ARE SPARKS (SPARK PLUG TEST)
After taking out the spark plug, reattach the plug wire. Now, hold the plug wire using insulated pliers, and let the threaded bare end of the spark plug touch a grounding surface (that is any exposed metal area such as a bolt). Ask your assistant to turn the ignition in the meantime. With the key turned, you should be able to see a bright blue spark at the end of the spark plug. If you do, your coil is working just fine. If you don’t, your coil needs change. However, even a poorly working coil can give out a small spark; thus, to be thorough, you need the bench test.
4 – USE PRIMARY AND SECONDARY WINDINGS (BENCH TEST)
Refer to your service manual for the correct resistance readings applicable to your car and model. Typically, for most automotive coils, a reading of 0.75 to 0.81 Ohms for the primary winding and 10,000 to 11,000 ohms for the secondary winding is valid. To check resistance, attach the multimeter/ohmmeter leads to the two outside poles on the primary winding. On the secondary winding, link one lead to either of the side poles and the other to the central high tension terminal. If the readings are even slightly outside the resistance indicated in your service manual, get your ignition coil changed.