35 12 Volt Ignition Coil Wiring With Ballast Resistor

Ignition Coil Diagram Wiring Diagram and Structur
Ignition Coil Diagram Wiring Diagram and Structur from wiringdiagram.calumcille.com


When it comes to the ignition system of your vehicle, the 12-volt ignition coil plays a crucial role. It is responsible for transforming the low voltage from the battery into the high voltage needed to create a spark in the spark plugs. However, in older vehicles, a ballast resistor is often used in conjunction with the ignition coil to ensure proper functioning and longevity. In this article, we will delve into the details of 12-volt ignition coil wiring with a ballast resistor, explaining its purpose, the wiring process, and the benefits it brings.

Understanding the Ignition Coil

Before we dive into the wiring details, let's take a moment to understand the basic functioning of the ignition coil. Essentially, an ignition coil is a type of transformer that boosts the low voltage (12 volts) from the battery to the high voltage (20,000 to 50,000 volts) required to create a spark in the spark plugs.

Primary and Secondary Windings

An ignition coil consists of two windings: the primary winding and the secondary winding. The primary winding is connected to the battery's low voltage circuit, while the secondary winding is connected to the spark plugs. When the primary winding circuit is closed, a current flows through it, creating a magnetic field. This magnetic field then induces a high voltage in the secondary winding, which is transferred to the spark plugs, resulting in combustion.

Need for a Ballast Resistor

In older vehicles, the ignition coil was designed to operate with a lower voltage (6 volts). However, as automotive technology advanced, the voltage was increased to 12 volts for better performance. To ensure the longevity and proper functioning of the ignition coil in these vehicles, a ballast resistor is used.

Understanding the Ballast Resistor

A ballast resistor is a device that limits the voltage supplied to the ignition coil. By reducing the voltage, it prevents the ignition coil from overheating and potentially failing due to the increased voltage. The ballast resistor acts as a resistor in series with the primary winding of the ignition coil, resulting in a lower voltage being supplied to the coil.

Wiring Process

The wiring process for a 12-volt ignition coil with a ballast resistor is relatively straightforward. Here's a step-by-step guide:

Step 1: Locate the Ballast Resistor

The ballast resistor is usually located near the ignition coil or the distributor. Refer to your vehicle's service manual or consult a professional if you're unsure about its location.

Step 2: Disconnect the Battery

Before starting any work on the ignition system, it's essential to disconnect the battery to prevent any electrical mishaps.

Step 3: Identify the Wiring Connections

Identify the wiring connections on the ballast resistor. There should be two terminals: one labeled "BATT" or "BAT" and the other labeled "COIL" or "IGN."

Step 4: Connect the Battery Wire

Connect the wire from the positive terminal of the battery to the "BATT" or "BAT" terminal on the ballast resistor.

Step 5: Connect the Ignition Coil Wire

Connect the wire from the "COIL" or "IGN" terminal on the ballast resistor to the positive terminal on the ignition coil.

Step 6: Reconnect the Battery

After completing the wiring process, reconnect the battery to restore power to the ignition system.

Benefits of Using a Ballast Resistor

The use of a ballast resistor in the ignition system offers several benefits:

Prevents Overheating

By limiting the voltage supplied to the ignition coil, the ballast resistor prevents overheating and potential failure of the coil. This extends the lifespan of the ignition coil and ensures reliable performance.

Protects Other Electrical Components

By reducing the voltage, the ballast resistor also protects other electrical components in the ignition system from excessive voltage. This helps prevent damage and ensures a more robust and reliable electrical system.

Maintains Optimal Spark Timing

The ballast resistor helps maintain optimal spark timing by providing a consistent voltage to the ignition coil. This ensures that the spark plugs fire at the right time, optimizing engine performance and fuel efficiency.

Compatibility with Older Vehicles

For owners of older vehicles, the use of a ballast resistor allows for the upgrade to a 12-volt ignition system without the need for extensive modifications. This makes it a cost-effective solution for maintaining the functionality of vintage vehicles.


The 12-volt ignition coil with a ballast resistor is a crucial component of the ignition system in older vehicles. Its purpose is to limit the voltage supplied to the ignition coil, preventing overheating and ensuring reliable performance. By understanding the wiring process and the benefits it brings, vehicle owners can maintain a well-functioning ignition system for their vehicles. Whether you're restoring a classic car or simply upgrading an older vehicle, the inclusion of a ballast resistor is a wise choice to ensure the longevity and performance of your ignition system.