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6 Reasons One Headlight Is Not Working?

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It happens to all car owners eventually. You switch on your headlights, and only one light comes on. That might be fine if you’re driving during the day but can be a real hazard at night.

We’ll dive into how to figure out what’s wrong and fix it.

6 Reasons One Headlight Isn’t Working?

Reasons One Headlight Isn't Working

There are a few reasons why one headlight might not be working, but the most common one is a defective bulb. Other causes can include a blown fuse, a damaged relay, or a problem with the headlight wiring. Read on to discover more:

1.    Old or burnt light bulbs

If one of your headlights isn’t working, the first thing you should do is check the light bulb. It’s possible that the bulb is old and needs replacement.

2.    Blown fuse

Your headlights might be broken because of a blown fuse. An electrical short or power surge can burn out your headlight fuse.

If a fuse blows, it affects the headlight’s electrical current flow, so the affected bulb won’t light up.

3.    Damaged relays

Another possible explanation for one headlight bulb not working is that the relays are damaged.

The relays are electrical switches that control the current to the headlights. When they malfunction, they may not be able to fully turn on the headlights, which is why only one light might be working.

4.    Damaged headlight assembly

It’s also possible that your headlight assembly is damaged if only one headlight isn’t working. The assembly includes the lens, reflector, and housing; a problem in any of these components can cause the headlight to fail.

5.    A problem with the headlight’s electrical connector

The electrical connector is responsible for supplying power to the headlight bulb; if it is not working correctly, the bulb will not receive power and will not be able to light up.

6.    A problem with the vehicle’s body control module

Another possibility is a problem with the vehicle’s body control module. This is the computer that controls all the electrical systems in the car, including the headlights. If it’s not working properly, it could cause one headlight not to come on.

If you’ve checked everything else and still not found your problem, visit a mechanic to inspect your car’s body control module.

How to Fix These Problems

How to Fix These Problems

There are many reasons why one headlight might not be working. Here are some common hiccups and how to resolve them:

1.    Inspecting and replacing burnt/old bulbs

You can check the bulb by removing it from the headlight and testing it with a voltmeter. If the bulb is faulty, you’ll need to replace it with a new one.

You’ll need to unscrew the entire headlight assembly from the car to replace the headlight bulb. This job is best left to a mechanic, as it can be tricky to do yourself. Once the headlight assembly is off, you can replace the old bulb with a new one.

Before shopping, check your owner’s manual for the correct bulb for your car, as not all bulbs are interchangeable.

2.    Fixing blown fuse

If the headlight is out because of a blown fuse, you can replace it yourself by following the guidelines in your car’s owner’s book.

3.    Solving relay problems

You can test the relays by turning on the headlights with the engine off. If one light comes on and the other doesn’t, the relay is bad and needs replacement.

4.    Correcting wiring problems

If you think one headlight is out because of a wiring problem, you can try looking for loose connections by checking the entire circuit. If you don’t notice anything, you may need to outsource the job to a mechanic.

5.    Fixing electrical connector issues

There are a few tricks to test if the electrical connector is working properly.

  • Method 1 is to test for continuity in headlight using a multimeter. If the multimeter shows no continuity, the electrical connector is likely not working and needs replacement.
  • Method 2 for testing the electrical connector is to disconnect and reconnect it. If the headlight bulb lights up when you do this, the connector is likely not the problem, but if it doesn’t light up, the connector is faulty.

The only way to fix a faulty electrical connector is to replace it. You can DIY if you’re handy with a soldering iron or take it to a mechanic or headlight specialist.

Once you’ve replaced the connector, your headlight should be working again. If it’s still not working, there could be another issue, such as a blown fuse, a broken wire, or a faulty connection.

6.    Solving headlight assembly problems

You can inspect the assembly by removing the headlight from the car. Shine a light on the lens and look for any cracks or damage. If you spot any faults, you’ll need to change the entire assembly.

If the headlight is out because of a lens or reflector problem, you can fix it using a headlight restoration kit.

Can I Drive with One Headlight Not Working?

Can I Drive with One Headlight Not Working

If one of your car’s headlights is out, you may wonder if you can still legally drive at night. The answer is no. Officers could pull you over for driving without proper headlights. Plus, it’s not safe to drive without being able to see properly.

So, if your headlight is out, replace it as soon as possible.

Wrapping Up

There are a few different reasons why only one headlight might be working. The bulb might be burnt out, the wiring may be faulty, or the headlight assembly might be broken.

The best way to find out what’s wrong with your headlights is to take them to a mechanic.  A professional will be able to check over the issue and correct it for you.

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