How To Test The Ignition Coil Of A Car

Update:Sep 27,2021
Summary:   In a car, an ignition coil converts 12 volts of energy from the battery to the thousands of volts required to ignite the spark plug. This part is a......

  In a car, an ignition coil converts 12 volts of energy from the battery to the thousands of volts required to ignite the spark plug. This part is an induction coil, simply put, a high-voltage transformer.

  Although ignition coils are generally very sturdy and reliable, they can become damaged over time due to heat, vibration, and insulation failure.

  There are two methods for testing automobile ignition coils: spark plug test and bench test. The spark plug test is effective, and the bench test is more thorough. Why? First of all, rely on sparks to determine the state of the coil; only when there is no spark, can it be determined whether the coil is faulty.

  In the second case, rely on resistance readings and data to test the condition of the ignition coil. Here, even if the coil is only slightly damaged, the reading will be displayed.

  Please read the correct instructions on how to perform these tests so that you can determine if the coil needs to be replaced.

  Step 1-take precautions

  When testing car parts, especially engines, one must be very careful. Before you start, be sure to wear safety goggles, do not wear loose clothes, and tie them neatly behind if your hair is very long.

  In addition, car engines generate electricity, so the greatest precautions should be taken to prevent any unfortunate incidents.

  Step 2-remove spark plug/winding

  For spark plug testing, first, remove the wire from the plug. It is recommended to use the vehicle's service manual to ensure that the correct wires are being removed. Then, with the help of the spark plug socket, remove the spark plug.

  If you are performing a bench test, please refer to the service manual and delete the two windings (primary and secondary) in the ignition coil.

  Step 3-check the spark plug test

  After removing the spark plug, reconnect the plug wire and hold the plug wire with insulated pliers so that the threaded bare end of the spark plug touches the grounding surface (any exposed metal area, such as a bolt).

  Let the companion start the ignition device at the same time. When the key is turned, a bright blue spark can be seen at the end of the spark plug. If so, the coil is good. If this is not the case, the coil needs to be replaced.

  However, even a poorly working coil will produce small sparks, so a thorough inspection requires bench testing.

  Step 4-Check the primary and secondary windings (bench test)

  Refer to the service manual for the correct resistance reading of the vehicle and model. Generally, for most automotive coils, the reading of the primary winding is 0.75 to 0.81 ohms, and the reading of the secondary windings of 10000 to 11000 ohms is correct.

  Check the resistance and connect a multimeter or ohmmeter to the two poles outside the primary winding. On the secondary winding, connect one wire to either side pole and the other to the center high voltage terminal. If the reading is slightly less than the resistance in the service manual, the ignition coil needs to be replaced.