Symptoms of Bad Ballast Resistor

Ballast resistor is an important component of the ignition system in vehicles. Its primary function is to regulate the voltage that is supplied to the ignition coil.

A bad ballast resistor can cause a range of problems in your car. In this article, we will discuss the symptoms of a bad ballast resistor, which will help you identify any potential issues with this component.

Symptoms of Bad Ballast Resistor


Difficulty Starting The Engine

If you are having trouble starting your engine, it might be due to a bad ballast resistor.

  • The engine cranks but does not start immediately
  • The engine starts and quickly stalls out
  • The engine requires multiple attempts to start

These symptoms can be caused by a ballast resistor that is failing to regulate the voltage to the ignition system. An insufficient voltage can result in a weak spark, making it difficult for the engine to start.

Additionally, when the ballast resistor fails, it can cause the ignition coils to overheat, leading to engine misfires and stalling.

If you are experiencing difficulty starting your engine, it is important to get your ballast resistor checked by a professional mechanic as soon as possible. Addressing the issue early can prevent further damage to your ignition system and improve the overall performance of your engine.

Engine Misfires

When it comes to the symptoms of a bad ballast resistor, engine misfires are one of the most common. This occurs when the engine fails to ignite properly or when the spark plugs don’t fire in the right order.

  • A bad ballast resistor can cause the engine to misfire at idle or at higher speeds.
  • Misfires can occur in one or multiple cylinders, and can affect engine performance and fuel economy.
  • A misfiring engine may also produce a rough idle, poor acceleration, and increased emissions.
  • Misfires can also cause damage to the catalytic converter, which can be costly to replace.

If you are experiencing engine misfires, it’s important to have your vehicle checked by a qualified mechanic. They can identify the root cause of the problem and determine if a bad ballast resistor is to blame. Prompt repairs can help prevent further damage to the engine and other systems in your vehicle.

Diagnosing/Replacing a Ballast Resistor Gone Bad!! // Engine Starts But Won’t Run? // NOTaRAODRUNNER

Overheating Ignition Coil

Overheating ignition coil:

Ignition coils are a vital part of the engine’s ignition system. They are responsible for converting the low voltage supplied by the battery into high voltage required to ignite the fuel. A bad ballast resistor can cause the ignition coil to overheat, leading to various engine problems.

  • Engine stalling: overheating in the ignition coil can cause the engine to stall frequently. This happens because the ignition coil is unable to provide enough voltage to fire up the fuel.
  • Misfiring: if the ignition coil overheats, it may not work correctly, and as a result, it will not produce enough voltage for the spark plugs to ignite the fuel in the engine. This can cause misfiring and lead to a reduction in fuel efficiency.
  • No start: an overheated ignition coil may not provide enough voltage to fire up the fuel. This can lead to a no-start condition even though the starter is cranking the engine.
  • Rough idle: a bad ballast resistor can cause the ignition coil to overheat and produce erratic voltage. This can lead to a rough idle, as the engine struggles to maintain a consistent speed.

To sum up, the ignition coil is a critical component of the engine, and when it overheats due to a bad ballast resistor, it can cause various problems such as engine stalling, misfiring, no-start, and rough idle. Therefore, it is essential to identify and fix the problem promptly to keep your engine running smoothly.

Dim Headlights

Symptoms Of Bad Ballast Resistor: Dim Headlights

Dim headlights can be a major cause for concern as they can greatly hinder visibility especially during night driving. The ballast resistor is responsible for maintaining the appropriate voltage to the headlights, and when it starts malfunctioning, it can cause the headlights to become dim.

  • Headlights appear dimmer than usual
  • Headlights flicker or pulse intermittently
  • The lights may not come on at all, or they may turn off unexpectedly
  • Hissing or crackling noises may come from the headlights
  • Other electrical components in the vehicle may malfunction

If you are experiencing any of the above symptoms, it is highly recommended that you take your vehicle to a qualified mechanic who can properly diagnose and repair the issue as soon as possible. Delaying repairs may not only worsen the problem, but it can also pose a safety risk by compromising your ability to see clearly while driving at night.



Stalling is one of the most common symptoms of a bad ballast resistor. It occurs when the engine suddenly stops running and eventually shuts down.

There are several reasons why stalling occurs when the ballast resistor fails.

  • When the ballast resistor fails, it can cause the engine to receive too much or too little voltage. This can lead to a failure of the ignition system and cause stalling.
  • Another reason for stalling is that the ballast resistor reduces the voltage that goes to the ignition coil. If the voltage is too high, the coil can get overheated and cause the engine to shut down.
  • Stalling can also be a result of a short circuit caused by a faulty ballast resistor. If the resistor is not working properly, it can cause a short circuit in the ignition system, which leads to the engine shutting down.

If you are experiencing stalling with your vehicle, it is important to have it checked by a professional mechanic as soon as possible. Ignoring this symptom can lead to more severe engine problems down the line.

Frequently Asked Questions For Symptoms Of Bad Ballast Resistor

What Is A Ballast Resistor?

A ballast resistor is a device that regulates the flow of current in an electrical circuit. It is used to control the amount of current that flows through the system.

What Are The Symptoms Of A Bad Ballast Resistor?

The symptoms of a bad ballast resistor include poor engine performance, frequently blown fuses, dim lights, and a burnt smell.

How Do I Know If My Ballast Resistor Is Bad?

To know if your ballast resistor is bad, you can do a simple continuity test using a multimeter or check for burnt areas on the resistor.

Can I Drive With A Bad Ballast Resistor?

It is not recommended to drive with a bad ballast resistor as it can cause further damage to the electrical system or even result in a fire.

Do I Need To Replace A Bad Ballast Resistor?

Yes, it is recommended to replace a bad ballast resistor as it can lead to other electrical issues and cause further damage to the system.


It is important to keep an eye out for symptoms of a bad ballast resistor in your vehicle. These symptoms can include engine performance issues, difficulty starting the car, and even problems with the headlights or electrical system. If you notice any of these warning signs, it is crucial to have your car inspected and serviced by a skilled mechanic as soon as possible.

By addressing the issue early on, you can prevent serious damage to your vehicle and ensure that you stay safe on the road.