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Signs of a Bad Xenon HID Ballast - Complete Guide

XenonPro - HID Headlight Conversion Kits - Signs Of A Bad Ballast

Lights often have multiple components and so when they stop turning on, figuring out which exact component failed is crucial to getting them to work again. Bulbs that do not turn on are not very useful, especially in cars while driving at night!

In this guide, we focus on ballasts, which are a crucial component of Xenon HID lighting systems.

We’ll go over the basics of a ballast, how to determine whether your lights are the subject of a bad ballast, some common reasons why ballasts fail and finish off with some frequently asked questions.

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What Is A Ballast?

In simple terms, a ballast controls and regulates the flow of power to the bulb to make sure it stays lit and does not over consume power in a fluorescent lighting system such as in Xenon HID headlight conversion kits.

With the absence of a ballast, the bulb would draw too much power, overheat, and burnout within seconds.

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Signs of a Bad Ballast

When looking to see if your lighting problems are caused by bad ballasts, the first step is to inspect and examine the ballasts physically. Physical signs of a bad ballasts include:

  • Burn marks
  • Swollen casing
  • Melted casing
  • Damaged/broken casing
  • Perforated casing
  • Oil leakage (older ballasts)

Although very uncommon, a ballast exhibiting any of these characteristics would be a strong indication of a dead ballast as a result of physical damage.

However, as mentioned, a bad ballast as a result of physical damage is unlikely unless you’ve been in a car accident or if the ballast was mishandled prior to installation.

In the majority of cases, a ballast “goes bad” as a result of a malfunction in one or more of its electrical components, which are sealed inside the casing.

Xenon HID headlight bulbs that are buzzing, dim/losing brightness, flickering, randomly turning off, changing colors, or if they are simply not turning on are not necessarily the victim of a bad ballast. In fact, the issue can be related to one or more of the other components found in lights.

So, how can you know if you have a bad ballast if it has no sign of physical damage? Through a series of small, non-technical, and simple troubleshooting tests.

Verify all your connections

Surprisingly, most lighting malfunctions are related to the simple problem of improper or loose connections. With time, some connections might come loose as you drive over bumps, rocky trails, and winding roads.

Make sure all your components are locked tightly, well connected, and plugged in all of the right places. If you find this to be a recurring problem, consider using some electrical tape to properly secure all your connection points.

If your lights work as expected after your connections are nice and tight, you’ll know the issue was not related to a bad ballast.

If you’re still having issues, continue to the next troubleshooting test - the Polarity Check.

Check the polarity

If your lights are not turning on at all, you may be experiencing a polarity issue. If your lights turn on but are experiencing other issues (flickering, dim lights, etc., skip over to the next troubleshooting test - the Bulb Switch Test).

Polarity is simply making sure the positive is connected to the positive and the negative to the negative. Reversing the polarity will prevent the flow of power and therefore, will prevent your lights from working.

If you’re still having issues, continue to the next troubleshooting test - the Bulb Switch Test.

Bulb Switch Test

The Bulb Switch Test is the most important and conclusive troubleshooting step in determining if you have a bad ballast.

In 99.9% of cases, only one of the two headlights is causing issues, which allows us to use the working headlight as our testing ground. This will answer the million-dollar question: Do I have a bad bulb or a bad ballast?

Let’s take a look at an example where the driver side headlight is working and the passenger side is not working.

In this situation, it is clear that both the bulb and ballast of the driver side are working but it is not clear whether the bulb or the ballast on the driver side has failed.

XenonPro - Signs Of A Bad Ballasts - Bulb Switch Test

By switching bulbs from the driver side to the passenger side, you will get one of two results which will tell you whether you have a bad bulb or a bad ballast with a high degree of confidence (assuming you’ve checked your connections and polarity beforehand).

Result 1 - Bad Bulb

Switching Bulb A with Bulb B resulted in the driver side no longer working and the passenger side now working perfectly.

This result tells us Ballast B is working after all since it lit up Bulb A, which was originally working with Ballast A. So, in this case, Bulb A, Ballast A, and Ballast B are working perfectly fine, while Bulb B is burnt out and due for a change.

Result 2 - Bad Ballast

Switching Bulb A with Bulb B resulted in the driver side still lighting and the passenger side still failing.

This result tells us that Ballast B is bad since it will not light Bulb A which was originally perfectly fine with Ballast A. So, in this case, Bulb A, Bulb B, and Ballast A are working perfectly, while Ballast B is bad and due for a change.

Using a multimeter

Another method of testing a ballast is through the use of a multimeter.

Simply put, a multimeter is a tool that measures a wide range of electrical data such as amps (current), volts, resistance, etc.

XenonPro - Signs Of A Bad Ballasts - Multimeter Test

By connecting the multimeter to the ballast, you will see right away whether you have a working or a bad ballast. If the multimeter measures and detects current, voltage, etc. you will know that your ballast is perfectly fine. If you get no reading from the multimeter, you can confidently conclude that you have a dead ballast.

Although it’s more technical than other troubleshooting steps and requires to have a multimeter, it is very accurate. A simple digital multimeter will only cost you about $10-$30.

Why do ballasts fail?

Ballasts can fail due to a number of reasons and in two general ways. A ballast can fail either due to internal electrical malfunctions or due to physical damage.

Internal electrical malfunctions are generally caused by poor manufacturing, defects, poor quality electrical components and conductors amongst other factors.

Ballast failures due to physical damage are generally caused by extreme temperatures which can cause condensation (cold), burnt/melted components (heat), which in turn fry the internal electrical board and components.

Extreme cases such as car accidents can break or perforate ballasts which will prevent them from working.

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Can I repair a ballast?

Technically yes, anything can be repaired. However, it requires advanced knowledge of electrical circuits/boards and the replacement cost is low enough such that it is not worth it.

Can I change a ballast only?

Yes. Ballasts are typically a separate components of lighting systems that can be changed without having to change the entire lighting system.

Is it easy to replace a ballast?

Yes. Replacing a ballast requires disconnecting it from the bulb on one end and the power supply on the other.

How much does it cost to replace a ballast?

Replacement ballasts cost anywhere from $40 to several hundred dollars depending on the lighting system and the type of ballast.

How do you test a ballast?

A ballast can be testing used the Bulb Switch Test or a multimeter.

How long do ballasts last?

A well maintained ballast can last up to 20 years, which is multiple times longer than a bulb’s lifespan.

How do you know if it's the bulb or ballast?

With the Bulb Switch Test, you can determine if you have a bad ballast or a bad bulb.

Will my lights work without a ballast?

No. Ballasts regulate the flow of power to a bulb. Without a ballast, the bulb will be oversupplied with power and burn out in seconds.

Are their different types of ballasts?

Yes. There are two general type of ballasts - dimmable light ballasts and non-dimmable light ballasts. Within these two types, there are different subtypes such as:

  • Rapid start (pre-heat start, low effeciency, low performance in cold temps.)
  • Instant start (instant start, medium effeciency, medium performance in cold temps.)
  • Programmed start (sensored start, high effeciency, high performance in cold temps.)
  • Prob start (electrodes start, low effeciency, low performance in cold temps.)
  • Pulse start (igniter start, high effeciency, high performance in cold temps.)

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