Headlight Out When You Hit A Bump? Causes & Solutions

Anytime you’re driving, you have to maintain razor-sharp focus, especially at night. Apart from being attentive, you rely on your headlights to enhance your visibility in poor lighting conditions. 

So why is it that the headlight goes out when I hit a bump? 

Well, the most probable culprit is a broken or loose connection in the headlight housing, particularly the bulb sockets. 

Each time you go over a bump, the socket loses contact. This then causes the electrical supply to get disconnected, which is why the headlight (s) goes out.  More on this below:

What Causes a Headlight to Keep Blowing Out?

There are several reasons why the headlights in your vehicle keep going out.

These include:

1. Loose connections

If there’s a loose connection to the bulb socket or the bulb itself, this can cause an intermittent disconnection in the electrical supply. Bulb sockets are the elements that link each headlight bulb to the car’s electrical system. 

Unfortunately, they are not immune to damage. Prolonged exposure to external weather elements can cause the sockets to wear out or corrode. Once this happens, the wires in the sockets can detach, disrupting the link of the electrical supply.

This explains why the headlight goes out every time you hit a bump.

2. Faulty electronics

One thing that many car owners don’t realize is that the headlights don’t work in isolation. They’re just a small part of a very intricate electrical system. This system is linked to everything – from the battery to the electronics on the dash and more. 

On that note, one of the most common causes of faulty headlights is voltage fluctuations. The lights function optimally when there’s a consistent supply of voltage. 

This means there shouldn’t be any abrupt dips or spikes in the power supply. If any of these is happening, it can subject the filament to unnecessary stress. Eventually, this can cause the filament to melt and blow out. 

These fluctuations are usually caused by a dying battery, blown fuse, or faulty alternator. Whatever the underlying problem is, I’d recommend taking your vehicle to a technician.

This expert has a good understanding of the car’s wiring and controls. They can determine whether the spike is being caused by a bad ground wire or something else, and fix the issue accordingly.

3. Excessive vibrations

Excessive car vibrations can cause the head- and tail lights to keep blowing out, especially when you go over a bump. 

To check whether the problem is being caused by vibration, inspect the bulb holder retaining spring. It should be clipped correctly so that it can hold the bulb in place. 

Next, inspect other systems that can cause excessive vibrations, especially those that affect alignment. The suspension springs and wheel bearings should be at the top of that alignment list. 

Why Does My Headlight Turn On When I Hit It?

If you have to hit the headlight so that it can illuminate, you’re probably dealing with loose connections. Hitting it reconnects the loose cables. This then allows electricity to flow as usual and power the headlamps. 

Have you been experiencing such an issue? If so, start by figuring out whether it affects the passenger’s headlamp, the driver’s, or both. Here’s a breakdown of the most likely scenarios:

One headlight not working

Have you noticed the passenger headlight going out, yet the other one is functioning just fine? If you have, the most likely culprit is a blown-out bulb. 

Although car headlights are exposed to a similar set of conditions, it’s very rare for them to fail at the same time. As such, it’s not unusual to have one bulb malfunctioning while the other continues working properly. 

But before you get rid of the faulty fixture, inspect the electrical connector for common issues like corrosion or damage. If there’s a loose wire, all you need to do is to push it back into position. Nonetheless, be sure to find out why the connection came loose to start with. 

Both headlights fail

If both headlights have stopped working, there’s a good chance that the bulbs aren’t to blame. Rather, there could be a problem with other components, such as the fuses, headlight relay, or headlight switch. 

That said, you may want to test the bulbs to verify that they’re working correctly. This troubleshooting procedure can be found on any forum community. But just in case you can’t find it, follow these steps. NB: You’ll need a good voltmeter for this.

1. Start by switching on the headlights. 
2. Take the negative lead on the voltmeter and connect it to a verified good ground
3. Next, connect the positive lead to the individual headlight connector terminals

If the bulbs are faulty or burned out, then one terminal will display the battery voltage while the remaining two display nothing. You can go a step further and test the high beams. 

Once you activate the high beam setting, the terminal should show a different voltage. If this is what’s happening, then you can be sure that the bulbs are burned out. This means you need to replace them to restore the light’s performance. 

Keep in mind that the diagnostic procedure differs depending on the type of headlights in your vehicle. The most common headlights in cars are halogen bulbs. However, some modern-day cars use High-Intensity Discharge (HID) bulbs that work differently. 

Halogen bulbs contain a filament that gets heated to generate light. Conversely, the HID light bulb illuminates by having electricity move between two electrodes found inside the bulb house. 

Although HID lights are more energy-efficient, they also have a more sophisticated circuit setup.

This configuration involves the use of a ballast to increase the voltage when needed. Unless you have any experience or expertise handling the ballast and other complex parts, it’s better to have a professional technician handle this task. 

Can a Blown Fuse Cause Headlights to Go Out?

Yes, it certainly can. 

Fuses play an important role in protecting the electrical components in cars. They do this by breaking the circuit anytime they detect an excess amount of power flowing through them. 

Depending on the make of your car, it could have one or multiple fuses for the lights. If any of the fuses blows, it can cause the headlights to malfunction as well. 

The fuse(s) is housed in the fuse box, which is located either inside the engine compartment or underneath the dash on the driver’s side.

Once you pop the hood, you’ll notice a variety of fuses inside this fuse box. However, the cover usually indicates the type of fuse. So for the lights, the cover will indicate that it’s a headlight fuse. 

The question is, how can you tell whether the headlight fuse is blown?

Well, this is easy to determine as the wiring element within the fuse will have melted or burnt out, causing the light to malfunction. This malfunction can happen in different forms. For instance, the lights can become dim or start flickering. 

Thankfully, all you need to do is to replace the blown fuse with a new one of the same amperage. Once you do, you’ll notice the lights will stop flickering and instantly become brighter. 

Conclusion

Wondering why the headlight goes out when you hit a bump? The most likely reason is that one of the cables connecting the headlight to the electrical system is broken or detached.

You’ll have to take the headlamp house assembly apart to check whether every cable is plugged in correctly.

If you don’t like the idea of inspecting the lights on your own, consider taking the car to your mechanic. They have way more experience doing such maintenance and diagnostic procedures.