How an Auto Ignition Coil Works: Explained in Simple Terms

by:Haiyan     2023-09-02

How an Auto Ignition Coil Works: Explained in Simple Terms


Understanding the workings of an auto ignition coil is crucial for any car enthusiast or mechanic. This small yet essential component plays a significant role in starting and maintaining the engine's ignition system. In this article, we will delve into the intricacies of how an auto ignition coil works, explained in simple terms. By breaking down the process step by step, you will gain a comprehensive understanding of this vital part of the engine.

I. The Purpose of an Auto Ignition Coil

An ignition coil converts the low voltage from a car battery into the high voltage needed to create a spark in the spark plugs. This spark ensures the combustion process, allowing the engine to run smoothly. Without an ignition coil, starting a car would be impossible, as the spark that ignites the fuel-air mixture wouldn't exist.

II. Primary and Secondary Circuits

The ignition coil consists of two distinct circuits: the primary and secondary circuits. The primary circuit receives a low voltage of around 12 volts from the car battery, while the secondary circuit can generate voltages exceeding 20,000 volts. These circuits work together to create the spark that ignites the fuel in the engine.

III. Primary Circuit Operation

1. Battery Power: When you turn your car's ignition key, battery power flows to the primary winding of the ignition coil.

2. Magnetic Field Creation: This electric current creates a magnetic field around the primary winding.

3. Breaker Points Open: Within the distributor, the magnetic field causes the breaker points to open, interrupting the primary circuit's flow.

4. Magnetic Field Collapse: As the breaker points open, the magnetic field around the primary winding collapses.

5. Inductive Kickback: This collapsing magnetic field induces a high voltage in the secondary winding, amplifying the voltage significantly.

6. Spark Plug Ignition: Once the voltage reaches a critical threshold, a powerful spark is created at the spark plugs, igniting the fuel mixture in the engine.

IV. Secondary Circuit Operation

1. Voltage Amplification: The secondary winding's design and the number of wire turns help amplify the voltage induced from the collapsing magnetic field.

2. Step-Up Transformer: The secondary winding acts as a step-up transformer, which significantly increases the voltage and allows for a strong spark.

3. Distributor and Wires: From the ignition coil, the high voltage travels through the distributor and spark plug wires, reaching each spark plug to ignite the fuel-air mixture.

4. Continuous Operation: The secondary circuit continues operating as long as the primary circuit is receiving a low voltage from the car battery.

V. Common Issues with Ignition Coils

1. Coil Failure: Over time, ignition coils can wear out or fail. This can lead to misfires, rough idling, and difficulty starting the engine.

2. Heat Damage: Excessive heat, often caused by poor engine cooling or high underhood temperatures, can damage the coil's internal components.

3. Electrical Problems: Issues with the power supply, wiring, or connections to the ignition coil can result in a loss of spark.

4. Moisture and Corrosion: Moisture and corrosion can interfere with the coil's functionality, causing erratic sparks or complete failure.

5. Overvoltage and Voltage Surges: A faulty voltage regulator or alternator can cause overvoltage or voltage surges, damaging the ignition coil.


An auto ignition coil is a vital part of a car's ignition system, converting low battery voltage into high voltage to create the spark that ignites the fuel-air mixture. Understanding its primary and secondary circuits, as well as common issues, allows for troubleshooting and proper maintenance. By grasping the mechanisms behind this small yet powerful component, you can have a better appreciation for the complexity involved in starting and running a car.

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