How to Troubleshoot LED Headlight Problems

August 12, 2021 6 min read

Automotive lighting technology has evolved rapidly in the last decade, and in many places, LEDs are now the norm. LEDs are brighter than traditional bulbs, use less power, and can last up to 50,000 hours — that’s more than 10x traditional bulbs! But as with most technologies, there is a learning curve. If your LED headlights aren't functioning properly you may be tempted to throw your hands up and call a mechanic. But fear not! We've got you covered with this guide on common LED headlight problems and how to troubleshoot them.

1. What to do if your headlights are dimmer than they should be

If your headlights are dimmer than they should be, it’s time to replace them. Headlights should be replaced every 5 years or so, and the best way to tell if they’re due for a change is to take a look at them. The bulbs should be clear, with no cracks or yellowing or a dull appearance.Also, there should be no mistaking the new bulbs for the old ones.
Unless the problem is a hardware or software issue on your end, it’s unlikely that replacing your lights is the cause of your lighting problem. The bulbs are probably dimmer than they should be, even if you’re not sure about the exact setting. And if your lighting problem is software-related, then either your headlight controller software isn’t recognizing the correct mode, or you need to update your firmware.
Most vehicle lights, including brake/turn signal, turn signal, parking brake, horn, windshield wiper, and lighting — are common hardware devices that need to be replaced periodically. Even with the millions of lights in your vehicle, it’s likely something needs to be replaced every few years. Likewise, automotive lighting hardware, which includes bulbs, fuses, and more, is a helpful artifact containing tons of information — including intermittent candle power levels, voltage drop, temperature readings, and more — that you can use as a diagnostic tool to identify lights that might need to be replaced, too.
To identify the cause of your lighting issues make sure you take a closer look at the following picture:
As you can see, the bulbs in my headlight aren’t functioning properly. Headlights are hot-swappable so this can happen from time to time. On the other hand, if you’re not seeing the error messages, even if the light is dimmers than it should be, then something is preventing the driver’s side light from working properly.
Inspecting the bulb socket and the wires coming out from the socket, and looking for obvious damage to the housing, is a good place to start troubleshooting lights.

2. What to do if your headlights flicker or flash on and off

If your headlights flicker or flash on and off, the problem could be a bad connection with the bulb socket. To fix it, remove the bulb and socket and then reattach it to make sure it’s secure. If the problem persists, you may need to replace the socket.
Having indicators on your dash that appear when you turn on your lights could be something to consider. There’s the N90 brake indicator that sits in line with the brake pedal. Check to make sure your bulbs are correctly installed and aren’t broken in the process.
If you have your light turned on while the car is moving, the indicator will flicker and can be frustrating. Helpful hints for increasing the longevity of your indicator include using a higher wattage bulb, like a 1500-watt bulb, and having it sit behind the windshield to ensure the most even light distribution. If your kids start throwing poop at your car, you’ll know they need more light.
Older models of automotive LED lighting may utilize a single-mode lamp that comes on when the headlamp is brightest and off when the light goes out. This is known as a pulsing or programmable beam, and you will need to test just how your current lighting setup works. In most markets it’s common to have a the headlamp come on for a brief second (depending on the vehicle), turn off for a few seconds (depending on the vehicle), and then come on again for a brief second before it goes off for a brief second. Other lighting systems may require the headlamp to be on for a longer amount of time to get a full, bright beam.
As these lighting systems are getting more complex, there are many different systems available with different levels of automation. Older systems commonly are simple enough that they will work manually. This is typically in the sub $300 bracket though you can still find systems that cost over $100K.

3. What to do if your headlights are too bright, even when turned down

If you’re driving at night and your headlights are too bright, it’s probably because you have a misaligned headlight. If the headlights are too bright, the best thing to do is to pull over and adjust them.
Motors need a steady and even supply of power from the electric grid in order to run. If your car’s battery is full, however, there isn’t much power to draw from the grid. As a result, power to the front of the car (which includes the headlights) will be “wasted.” To understand this problem, it’s important to know exactly what happens when your headlights draw power from the battery in your car.
When you turn on, on, or off your car’s lights, a circuit forms between your headlights and the battery. This circuit uses voltage to open and close a switch which in turn turns on and off the main power supply to your headlights. When the voltage provided to the GPU in the driver’s side of the headlights reaches a certain level (usually around 1,000 V), another voltage is provided to the driver’s side control module or “NCM” (red unit in the diagram above) to turn on a signal to the outside world. With enough power, larger bulbs will light the road ahead more brightly than the tiny lights in your headlights.
At first, only the CCM inside your vehicle will be affected by a blown power line. When that happens, it is important to identify exactly which side of the vehicle the power is coming from. A blown power line will most likely be on the driver’s side of the car where the alternator powers the overhead wiring. You will need to inspect your bumper wiring to identify the intermittent power line. If the intermittent power line is located on the passenger side of your car, you may in theory be able to simply disconnect the power at the switch and the bulbs will turn off.

4. What to do if your LED lights burn out prematurely

There are a few things you can do if your LED lights burn out prematurely. First, check the batteries. If the batteries are weak, then your lights will dim and may occasionally turn off. If you’re using rechargeable batteries, check to make sure they’re fully charged.Most batteries should last for around 5,000 hours, but some won't last much longer than 2,500. Recharge them by walking into a lit parking lot, as that can cool the temperature of the battery enough to get it charging. Hope for the best!
Next, you’ll want to check the circuitry. Make sure there isn’t a short between the circuits in the headlight and the circuits on the windshield. You’ll want to test the vicinity of the bulb to be sure this isn’t the problem.
Things to Try
If your bulbs don't turn on to begin with, try switching the bulbs out for high-Watt bulbs. LED lights that shine through the windshield actually have a slightly lower maximum intensity than other bulbs. (Check your nearest shopping center to see what level of bulbs are in use.) If your bulbs don’t light up, you can try swapping them out for extra-bright or double-dipped bulbs, which have a higher range of brightness.
Also, try shimming the inside and outside of your windshield. This isn’t recommended if you’re going to be parking in an area with any wind, hail, or other forms of precipitation, because the windshield is likely to get very wet. But if you want to take your car out on the weekend and the front end is not very flexible, this can work.
Be sure your windshield wiper blades are original style. Most new windshield wipers have “proper” electric wipers built into them, and that’s the only style that will allow your LED headlights to work correctly. If your wiper blades actually stopped working on their own, they should be replaced.
Check the intensity of your high beams.


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