Both Headlights Not Working: Causes and Fixes

We rely on our car’s headlights to lead the way at night when it’s raining or foggy and generally when visibility is low. Thus if your headlights aren’t functioning correctly, it could mean disaster for you, your passengers, as well as other drivers.

Unfortunately, like any other mechanical or electrical component inside your car, headlights are vulnerable to damage and the occasional malfunction. So what do you do when both headlights are not working and why it happened?

why both headlights not woring

What causes both headlights to stop working?

To fix your headlights, you first need to diagnose the problem. There are several potential reasons why one or both headlights might stop working in your car. The most common reason why both headlights stop working relies on the relay harnesses. Because the relay harness essentially controls both lights simultaneously while other components such as ballast, ignitor, or the bulbs completely work as independently. So it is kind of obvious that the relay harness is the main culprit of stopping the both headlights at the same time.

However, other things that can cause a malfunction or failure with headlights include blown fuses, broken bulbs, faulty wiring, ice build-up on the headlight units, oil leaks from the lamps, and even collisions that damage them.

Bad Relay Or Blown Fuse

A blown fuse or bad relay can be the main cause of malfunctioning headlights. Check your car’s manual for the location of the headlight fuse. Replacing it is relatively easy. However, replacing the blown fuse with one of the same amperage ratings is important.

If the fuse is not blown and the headlights are not working, the culprit may be a bad relay. Shaking the headlight relay is easy to check if it’s damaged. If you hear rattling inside it, it’s a good sign that it is not in good shape.

bad relay

Alternatively, check for discolored terminals, indicating a defective relay. You can also switch the headlight relay with another functioning one to test if it is the cause.

Improper Wiring Connections

If your car has aftermarket headlights such as HID headlights, you may experience problems with them. This is most often due to poor wiring connections during the bulbs’ installation.

The poor wiring will result in both headlights not working or one. You may also notice the bulbs flickering or functioning intermittently. The solution will be to have the headlights installed again and the poor wiring connections redone.

Poor Ground Connection

HID and LED lights two come with a ground wire that has to be attached to a metal part of the vehicle. If this wire is not connected correctly, it may lead to both headlights not working. Ideally, the connection should be made to rust, paint, or dirt-free metal part.

A common mistake when installing headlights is failing to remove paint, rust, or dirt from the metal part where the ground is connected.

How To Fix If Both Headlights Not Working?

Replace The Fuse or Relay

In most cases, the cause of both headlights not working is a blown fuse or bad relay. Replacing these parts will fix the issue. However, the fuse may be blown due to an underlying problem with the wiring. 

If you replace the fuse and it blows out after a short time, it may be due to a wiring problem in your car.

Wiring Problem Fixes

If your car has underlying wiring problems, it will cause other parts of the headlights to get damaged quickly. Fixing bad wiring issues will require expert assistance. Taking your car to a mechanic for a diagnosis will be the best cause of action.

Fix hedlight wiring problems.

Replace the Ballast

A damaged ballast can be the cause of HID lights not working. Check the ballast to inspect its condition. Inspect the casing for damage or swelling, indicating damage due to power overloads. You may also notice burn marks when you open the ballast casing.

The ballast may cause your headlight to flicker or stop working altogether. Though HID bulbs have separate ballasts. Thus, a problem with the ballast will manifest as one headlight not working. 

Replacing the ballast will fix the issue. However, in most cases, both bulbs’ ballasts may be damaged, requiring you to replace both. 

What To Do When Headlights Stop Working While Driving

If your headlights stop working while driving, there are a couple of things you need to do

  • First, you need to pull off the road and away from traffic. Ensure your hazard lights are on when you pull off the road. This will help other cars see you. 
  • Check the fuse; As already stated, headlights will often stop working due to a blown fuse. Check your fuse to see if it’s blown. If it is, you can swap out the blown fuse with the one you are not using, such as your car radio fuse, if it’s of the same amperage rating.
  • If no fuse is blown, check to see if your high beams work. If they do, they can offer a temporary solution for you to get home where you can better diagnose the problem. In this scenario, try to stick to side roads and avoid the main highway to minimize the risk of blinding oncoming drivers.
  • Once you are home or where you can get the car fixed, diagnose the fix the headlight problem immediately.

Cost of Headlight Repair

It can cost you anywhere between $75 and $200. However, this is if the entire assembly is being replaced. If only replacing the bulbs, bulbs will typically cost between $15 and $20. However, HID bulbs can for upwards of $100 and cost $50 to install. 

Frequently Asked Questions

How long do Halogen and HID bulbs Last and When To Replace

Traditional halogen bulbs typically last for up to 1000 hours. On the other hand, HID bulbs will have a lifespan of up to 2000 Hours. In some cases, they can last for up to 8000 Hours. It is important to replace the bulbs when you notice them become dimmer than usual. Bulbs become dimmer with age.

Can A Fuse Cause Both Headlights To Go Out?

Most cars today have separate fuses for separate headlights. As such, a blown fuse cannot cause both headlights to go off unless both fuses get blown simultaneously. And if this happens, it may be due to wiring issues.


The components that make up a headlight are pretty simple to understand, and it is possible to fix some of these issues yourself. The only complication may be due to wiring issues. If the wiring is the culprit, you may have to get the car checked by an expert. The wiring inside your car can be pretty complex.

Trying to fix it yourself without proper tools or knowledge or what goes where may cause more harm. 

Last Updated on March 20, 2024 by Rifen

Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top