How To Tell If Headlight Bulb Is Bad

In this article, we’re going to look at signs that a headlight bulb is bad.

We normally take out the toolbox and start tinkering with the car when the weather is warm and sunny. Ironically, that’s not when we’re thinking about headlights at all, and thus these critical components often become the orphans of vehicle maintenance.

And this is just plain silly. If they don’t function well, they become a danger to yourself, and everybody else on the road. And they are the easiest components imaginable to maintain. That is if you know what to look out for.

Keep reading – we’re about to tell you.

Signs Your Headlight Bulb Is Bad

There are always telltale signs that a headlight bulb is about to blow. Scan through this list and see if any of these apply to your vehicle.

Dim headlights

If your headlights are becoming dimmer than usual, that’s a sure sign of failing headlight bulbs. Look, these little marvels weren’t designed to last forever. A standard halogen headlight bulb has an expected lifespan of around 400 hours of continuous operation. And that’s excluding road and environmental hazards that will also influence how long it will last. But – rule of thumb – if the lights start to go dim, check the bulbs.

Your headlights become intermitted

If your headlights start to flicker, that’s also a sign to check the bulbs. The filaments become worn over time, and the bulb will usually blow shortly after it reaches a tipping point. But while you’re at it, also check the wiring harness around the headlight for loose connections.

Headlight not working at all

Again, if this is the case, checking your headlight bulb is your first course of action. If it is a blown bulb, replacing it is a DIY job that will take you no longer than ten minutes, with no technical expertise.

Can You Fix A Bad Headlight Bulb

Because halogen headlight bulbs work with filaments (much like the lightbulbs in your home,) the answer is no. They can’t be fixed. That said, though, a headlight bulb is not an expensive part, so replacing it won’t break the bank.

How To Fix A Bad Headlight Bulb

Here is a list of step-by-step instructions on how to replace a dead headlight bulb. As you read through it, notice that you don’t need any experience or expertise at all to do this. It’s one of the simplest automotive maintenance jobs there is.

  1.  Identify the blown lightbulb – which means, make sure it is a blown bulb, and not something else. Remember, some vehicles use a single bulb for low and high beams, so make sure by testing on both.
  2. Get the tools together – some cars require no tools. Housings and bulbs work with clips. In other vehicles you may need a Philips or flat screwdriver, but seldom more than that. Refer to your owner’s manual if you are unsure. It normally has a section on changing lightbulbs.
  3. Disconnect your car’s battery – this is not for your safety, but to protect the electrical system of your vehicle against accidental shorts.
  4. Remove the necessary pieces of trim – this will differ from vehicle to vehicle. Some cars have the headlights embedded in the vehicle trim, while with other models you can simply slip the headlight housing out by undoing a clip or two – simply refer to your owner’s manual again.
  5.  Find the bracket that holds the headlight – newer cars make use of plastic housings for the headlights. Older cars have a metal bracket. Either way, remove the holder or bracket and remove the wiring harness. All it should take is a quarter turn counterclockwise.
  6. Gently pull the bulb from the headlight housing. Do this with your thumb and forefinger, without exerting too much pressure.
  7.  Make sure to handle the new bulb with a glove, or tissue around your fingers. Slide it into place.
  8. Reinstall everything by doing the above steps in reverse, ending with connecting the battery again.

 Now you’re ready to test!

A parting shot

As you can see, replacing a lightbulb is a piece of cake. Absurdly simple, if you think of the danger and discomfort it can cause if it blows. Keep your eyes open for signs of a bad headlight bulb, and ensure you stay safe and comfortable on the road at night!

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Richard Nickleson is the author and owner behind Headlight Reviews. He first started the site as a hobby to share his insights on car parts and specifically headlight bulbs, but it soon ballooned and now he writes on all topics surrounding headlights bulbs. If you've got a bulb question, contact Richard here.