Why Do My High Beams Keep Turning On?

I have heard about an incident that happened to my friend’s vehicle. He was driving down a dimly lit road while focusing on his path ahead. Suddenly, his car’s high beams flipped on, like bathing the entire highway in blinding light. Then, he thought, “Why do my high beams keep turning on?”

Something is wrong if your car’s high beams keep turning on without your command. It may happen due to several reasons. Typically, it occurs for a damaged fuse, a broken switch, a defective headlight relay, or a faulty bulb. It may also occur due to a malfunctioning sensor system that controls high beams.

Well, you do not need to worry if you face such a situation as my friend did. In this blog, I will illustrate the causes of high beams going out of control. Besides, I will suggest solutions to make your nighttime drive safer.

High Beams, Their Functions,& Relationship to Constant Turned-On

Knowing the functionalities of high beams can help deal with its errors. These components are also known as brights (1). In other words, they are a type of headlight function in vehicles to project light about 350 to 500 feet (2). This light projection provides more powerful illumination during night driving and in poorly lit areas.

High beams can be manually activated by pushing or pulling the turn-signal stalk. But some modern vehicles can switch on and off automatically without triggering them(3). Likewise, these cars use a single bulb with two filaments to perform the work of both high and low beams (4).

Let me add more! Any car headlight has four essential components: bulb, relay, fuse, and switch (5). Suppose you switch on the high beams. Then, the current to the low beams is cut off to ensure the maximum luminosity of the high beams(6).

The switch for activating high beams can vary depending on your car. For instance, some vehicles have dual-beam headlights. In these cars, the high and low beams are controlled by the same light bulb.

Common Causes of High Beams Turning on Unexpectedly

As you see, there are multiple components of any high beam. You will get inconsistent or uncontrollable high beams when any of these components go wrong. In this part, I will share why high beams keep on.

Reason: 1 – Faulty Headlight Switch

Yes, every car has a light switch to control different lighting modes (like high and low beams). When the switch becomes defective, it automatically turns on the high beams. Usually, it happens due to wear and tear, a short circuit, or other mechanical issues.

According to Your Mechanic, these are the symptoms of a faulty light switch (or headlight dimmer switch) of high beams:

  • You will face problems switching between high and low beams.
  • Headlights will stick to one setting (like keep turning on).
  • The headlights will not turn on or function effectively.

What to Do

If you see any of the symptoms, start diagnosing the light switch. It may need the assistance of a professional mechanic.

Reason: 2 –Damaged Fuse

The fuse in your car protects the wiring from damage. But it may blow due to some reasons like these (7):

  • When excessive current is drawn through the brights circuit, you will get a blown fuse.
  • Short circuits may also blow a fuse that helps to control power to high and low beams.
  • When you install bulbs of incorrect wattage, you may damage the fuse.

Some signs of a blown fuse are (8):

  • Headlights dim, go out, or keep turning on.
  • Sudden failure or stalling of the engine.
  • Bizarre noise from the car’s electrical system.
  • Burning smell from car parts.
  • Melted or burnt fuse.

Why am I talking about the fuse? Well, when it cannot protect wiring, the high beams may not get enough orexcessive current. As a result, these lights will keep turning on.

What to Do

Check the condition of the fuse to see if your high beams keep turning on. If you get the fuse blown or get those symptoms I have mentioned, replace it with a new one.

Reason: 3 – Defective Headlight Relay

As I said, the headlight switch controls the bulbs (or high beams). But it can be controlled through one or multiple relays (7). Hence, the switch powers  the relay, which turns on the headlights. It can shield the switch from the high current to turn on high beams.

Some symptoms of a defective headlight relay are (9):

  • No low or high beams.
  • Irregularly active headlights.
  • The headlight is always on.

You may not switch between high and low beams when the headlight relay is broken or non-functional. As a result, the headlights will remain locked in single mode. Moreover, you may not see ahead correctly and blind the other drivers from the inverse direction (10).

What to Do

If your headlight relay becomes erratic or shows symptoms, you must repair or replace it soon. In this case, my suggestion is to call the nearby mechanic. It is because these components are not easy to handle for a non-professional.

Reason: 4 – Blown or Incorrect Headlight Bulb

According to sources (7, 11), a blown or headlight bulb can cause problems with high or low beams. For instance, if you get only one headlight working, possibly the other one is blown. In this case, the active high beam headlight will keep turning on. Otherwise, it may turn into low-beam mode.

Then, cars with HID headlights or solid-state circuit protection require the correct bulb to use the high and low beams. If you install the wrong bulb, you will get either constant, uncontrollable, or no high beams. In such a condition, the wrong bulb will draw excessive current and keep the high beams on and on.

What to Do

Check the condition of the headlight bulbs. Bring the right and recommended one if you find any of them blown. Then, install or plug it into the right place in the right way. You may also get help from the expert mechanics.

Reason: 5 – Malfunctioning Sensors

You can get an Auto High Beam feature in many of the latest car models. It uses sensors to automatically switch between high and low beams based on the ambiance and traffic. However, these sensors can malfunction for various reasons, like dirt, debris, or technical issues. And when they do not work, you will get unexpected turning on of high beams (12).

What to Do

You may not deal with sensor issues yourself unless you have sufficient knowledge and tools. Primarily, you can use a soft cloth to wipe the sensors gently. But you need to make sure not to scratch or damage them. If this doesnot work, the sensors might need to be replaced (13).

So, again, my suggestion would be to call the dealership to investigate this issue. They will come and see the condition of the sensors.

Frequently Asked Questions

Why do my high beams keep turning on and off unexpectedly?

Answer: Some reasons work behind high beams do not turn on or stay on forever. These include a bad headlight relay, a faulty alternator, a defective battery, a broken headlight dimmer switch, and wiring issues.

Can I drive with my high beams on all the time?

Answer: Many car experts suggest not to use the high beams continuously. This is because they can drain your vehicle’s battery quickly. Also, they can be blinding for other drivers. But you can use them where visibility is poor, like in the dark road.

Are high beams bad?

Answer: Brights or high beams are good until you use them to increase visibility. But when you use them nonstop, they can harm the eyes of oncoming drivers. It can cause severe accidents by blinding them suddenly.

Conclusion: Why Do My High Beams Keep Turning On?

If you get consistently turned-on high beams, you may have a tough time at night or in the evening. May be you are a few inches away from having an accident by blinding the drivers coming towards you.

You should consider solving the issue and finding its root cause. And I have explained multiple reasons for having uncontrollably high beams.

Throughout the blog, I have explained why the issue happens and their possible solutions. But you can avoid the problem by preventing the reasons from happening. For this, I suggest you check your vehicle regularly. Check the headlights, switch, fuse, relay, and sensors. If they are in good condition, there will be no issue.

I hope you will follow my instructions. Thanks for reading this blog!

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