What Is a Headlight Ballast?

Ballast is a component you can install in your headlight system or already have if your vehicle has stock HID lights. If you are new to this term, ballast can confuse you. After all, you constantly hear of it when there is a talk about HID headlights.

The thing is, ballasts act as a regulator for voltage and electrical arc to the bulb. Without it, your HID headlight won’t function to its full potential, and you will be wasting so much energy. This article will explain them adequately to you to remove your confusion.

Headlight Ballast

What Are Ballasts and Why Are They Necessary?

Ballasts are electrical devices that can control the flow of electric arc and voltage towards the bulb. You don’t need it for halogen and LED headlights because none of them needs a high voltage to light up. However, an HID bulb requires an extreme voltage to turn on. After the arc is provided, it can run on a lower voltage, which is still higher than what halogen and LED need.

Because of this, high-intensity discharge (HID) bulbs require something that can give them that high amount of voltage. Ballast is the device that can effectively tackle that duty.

Meanwhile, it can also regulate the voltage to keep it steady. Hence, you get a stable output from the HID light. Without it, the bulbs can dim or brighten. A dim headlight doesn’t let you see well in the dark, while a bulb that provides more brightness than its limit can break quickly.

Some ballasts can also convert the DC power from the power source to AC. HID bulbs need AC power to run, which they can get from the ballast. Without it, your HID bulbs can consume more power while getting less electricity. As a result, you get yourself a headlight setup that wastes high energy while giving you a dimmer brightness than usual.

A faulty ballast can cause the bulbs to flicker. Also, note that the buzzing you hear from HID bulbs is actually from a malfunctioning ballast. Now you can see how essential ballasts are for HID lights.

Why Headlight Ballast

Factors to Consider When Buying Ballasts

You shouldn’t just bring any random ballast for your vehicle; you need it to be suited and perfect. You should consider these factors when buying them-

Whether Do You Need the Ballast or Not

Vehicles with factory HID headlights already have a ballast in them. It means you don’t need to buy one. Although, if the stock ballast gets faulty, you should replace it. Meanwhile, if you convert from halogen to HID, we suggest getting a complete kit containing the bulbs, ballasts, and wiring.

Wattage Rating

Ballasts come in 35W, 55W, and even 70W ratings. However, you shouldn’t jump to a high wattage one, thinking it will provide a brighter output. Yes, higher wattage can affect the brightness. But HID bulbs have their own wattage rating.

If you put a 55W ballast on a 35W bulb, the bulb will get more power than it can work with. It can result in the bulb burning out quickly or blowing. Meanwhile, getting a ballast with a wattage lower than the bulbs can hinder the HID light from showing its full potential of brightness. Hence, get ballasts that match the wattage rating of the bulb.

Headlight Ballast Buying Consideration

CANBUS Ballasts

Some automobiles like Jeep or Ford utilize a system called the CANBUS that keeps a connection between many electrical components of the vehicle. It also shows you error codes when there is any problem with these devices. Headlights also fall into their network of communication.

HID bulbs consume lesser electricity than the stock halogen bulbs of vehicles. So, when you upgrade the factory halogen headlights with HID, the CANBUS system thinks that the bulbs are not working.

So, you get error codes. The system also tries to restart the bulbs, causing flickering. It is more common in LED headlights but can also happen for HIDs. Getting a CANBUS ballast can solve this issue. However, remember that not all vehicles have a CANBUS system.

So, only get a CANBUS ballast if your vehicle has the system.

How to Replace Headlight Ballasts

Changing the headlight ballast on your vehicle is quite straightforward. If you were to upgrade your headlights from halogen to HID system, you would need to go through many complex steps, including installing both the bulbs and ballasts. But a vehicle that already comes equipped with a ballast system is perfectly suitable for new ones. Simply follow the steps below-

  • Take out the whole headlight housing and place it somewhere.
  • Locate the housing on the back or bottom of the housing.
  • Next, remove the old ballast. Depending on your vehicle model, there can be screws, clips, etc., you need to take out.
  • Finally, install the new ballast in reverse.


If you consider upgrading your halogen headlights to HID, you must spend some money on a quality ballast. Make sure that the ballast has the exact wattage rating as the bulbs. Try not to compromise on a low-grade item to save some money.

Since HID systems last longer than the traditional lights, you won’t need to replace them occasionally. A quality ballast may last for 3-5 years, depending on your use.

If your headlight ballasts show symptoms of malfunctions, check them quickly and troubleshoot or replace them as necessary.

Leave a Comment