Both Low Beam Headlights Stopped Working – Causes & Fixes

Rainstorm and night driving have their drawbacks. You rely heavily on the headlights during these conditions to provide clear visibility. If the headlights are not working correctly, you and other drivers are in danger because you won’t see and be seen clearly. This greatly increases the risk of road accidents.

Read this article to the end if both low-beam headlights stopped working on your car. Here, I’ll outline reasons for low-beam headlights not working and how to track and fix the culprit. Let’s start with the possible reasons to look into when tracking the root cause of the problem.

high beam headlights not working

What causes both low-beam headlights stopped working

The importance of functioning headlights cannot be overemphasized. If the low beams are not working, but the high beams are, it may look like a good idea to use the high beams. But this has its drawbacks as well. Using high beams when you’re supposed to use low beams will blind oncoming drivers, invariably increasing the chances of road accidents.

There are several possible causes if the low beam headlights are not working, but the high beams are. Here are the potential reasons to look into.

Burnt bulbs

Let’s get this clear; it’s nearly impossible for two headlights to fail simultaneously unless the bulbs are not to be blamed. A dead bulb is usually a common parameter to inspect when only one low beam headlight is not working.

However, modern headlight bulbs are much brighter than their older counterparts. For this reason, you may not even notice when one headlight goes off. You’ll be cruising with the vehicle until the second one burns out.

Blown fuses

Vehicles come in different designs. Some vehicles may have one fuse that controls both low beam headlights, while others may have one for each low beam headlight. So if your low or high beam headlights are not working, locate the fuse box and check the headlight fuses.

If you detect any blown fuse, replace it and see if that rectifies the underlying problem. If the fuse burn out the second time, you have severe electrical issues that need to be addressed before replacing the fuse. Follow the guide in the next section for comprehensive detail on how to diagnose headlight problems.

Wiring issues

Wiring issues can blow a fuse. It can also cause problems in several ways. Sometimes, a wiring issue will not blow the fuse, but it’ll prevent the light bulbs from coming on. Since electrical wiring in cars is so complex and can cause fire outbursts, it’s better to have experienced technicians track and rectify the root cause of any wiring problem.

Headlight relay

This article will be incomplete without mentioning the headlight relay. The headlight switch in the cabin is not directly connected to the headlights. They’re connected to the relays. Therefore, once you flip the switch, it activates a relay. The relay transmits the required electric voltage to the headlights.

The low beams have different relays from the high beams. So, if both low beam headlights stopped working but high beams works, you likely have a blown headlight relay. The best solution would be to replace the dead relay.

How to fix both low-beam headlights stopped working?

I have outlined reasons why my low beam headlights are not working. Now, you may be wondering, how do you fix low beam headlights not working? There are several causes of this issue; therefore, there are several feasible solutions.

Replace blown fuses

Blown fuses are the most prevalent reasons why headlights go out while driving. Hence, it is best to start the diagnosis from the fuse. There are usually two fuse boxes in vehicles—one underneath the steering wheel and the other inside the engine bay. Start checking the headlight fuses in the fuse box underneath the engine bay.

Follow the diagrams on the fuse box cover to locate the headlamp fuses. Some vehicles have two to four fuses for the headlamps alone. Ensure you check all these fuses and replace burnt ones accordingly. 

Note: Do not stop at one fuse. Check all the headlamp fuses even if you detect a blown fuse. This is because there could be more than one defective fuse since both the low beam headlights are not working.

Replace dead bulbs

As reiterated above, a headlight bulb can die in several ways. The low beam can stop working while the high beam is still working. If diagnosis proves dead bulbs are the root cause of the problem, the best solution would be to replace the bulbs with new ones.

Check and replace defective relays.

If the bulbs and the fuses are in good condition, narrow down the diagnosis to the headlight relays. The relays are placed inside the fuse boxes, mainly in the engine bay. Open the fuse box, locate the headlight relay and examine it.

If you can’t detect a lousy relay, swap the headlight relay with another functioning relay of the same size. You can check this article – how to tell if a relay fuse is faulty to help determine if the relay is the leading cause. If the relay is the culprit, replace it as needed.

Contact a service technician.

If the bulbs, fuses, and relays are in good condition, it could mean you have wiring issues. Contact an experienced technician to track and rectify the leading cause. The technician will run a professional diagnosis and proffer solutions in no time.

Frequently Asked Questions – FAQs

Q: Is it common for both headlights to fail at the same time?

Even though both headlights are turned on at the same time, it is rare for both headlights to fail at the same time, but you can’t rule it out. Therefore, if both led headlights only work on high beams or don’t work at all, you likely have electrical issues like a blown fuse, blown relay, or headlight switch issues.

Q: Can a fuse cause both headlights to go out?

Different car manufacturers use different technologies and designs in producing cars. For example, a manufacturer may employ one fuse to control both low beams and another to control both high beams. In contrast, another manufacturer protects each low and high beam with individual fuses.

Depending on your vehicle design, a single fuse can cause both headlights to go out. Plus, two fuses can blow at the same time and prevent the headlights from coming on.

Q: Where is the low beam relay located?

The low-beam headlight relays are usually located in the power distribution box (fuse box) in the engine compartment. The fuse box is a black rectangular box in the left-hand side firewall.

The fuse box cover has a diagram that shows you how to locate the fuses and relay inside the box. Follow the instructions to detect the relay easily. Consult your owner’s booklet if you do not find the low beam relay here.

Q: Are high beams and low beams on the same fuse?

The low and high beams are wired on different circuits in most vehicles. This way, a low beam can stop working while the high beam is still working. Some manufacturers wire both low beams on the same circuits and the high beams on different circuits, while others use one fuse for each beam on each side of the headlights.

Q: How much does it cost to replace a headlight relay switch?

Headlight relay replacement is affordable and simple as replacing fuses. It is an easy DIYer repair that anyone can do with the right guide. If you decide to replace the headlight, relay yourself, budget to spend between $15 and $30. But if you want a technician to replace it, budget between $50 and $100.

Q: Are my high beams and low beams the same bulb?

Most older cars have two bulbs for low and high-beam lights. Newer cars use one bulb for low and high bulbs. The headlights on each side have two filaments, one for low beams and the other for high beams.

Q: Is it illegal to drive around with high beams?

According to accident law or traffic law, driving with bright lights are not illegal. However, motorists driving at night are advised to use high beam headlights for clear visibility. In any case, you should note that driving with high-beam headlights may blind approaching drivers, increasing the risk of an accident.

Final Words

Several factors like wiring issues, blown fuses, blown relays, and burn-out bulbs can cause both low beam headlights stopped working. Luckily, how to diagnose headlight problems is straight to the point and easy to understand.

Follow the diagnosing procedures above to track and rectify the root cause of the problem. However, if you’re unfamiliar with the underhood working principles, contact a service technician to track and resolve the issue.

Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

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