Flashing headlight: what to do?

On board a vehicle, it is recommended to always fasten your seat belt. However, at night, it is important to ensure the proper functionality of the lighting to guarantee your safety. The headlight is the component known for fulfilling this role. Have you noticed that your vehicle's LED bulb is flickering? Don't panic! Here are a few steps you can take.

Check the flickering headlight

For a flickering headlight, the first reflex should be to locate the fault by performing a few checks. Is your LED bulb worn out or at the end of its life? Should it be replaced or repaired? Check if the LED has any damage, signs of overheating (black spots on the SMD chips), or wires that might be slightly stripped.

If the LED does not show any visible defect, perform an isolated test with a battery and connect two wires (+) (–) to power it directly. Check that it does not flicker in this context and that the fan operates correctly. This test allows you to accurately target the LED fault without the vehicle's electrical system interfering with your diagnosis.

If you notice any of these problems, replace the faulty bulb with another one. If the issue persists, the malfunction is most likely in the electrical circuit.

Check the stability of the electrical network and the contacts

A flickering LED bulb can indicate voltage variations in the electrical circuit, as the LED system is sensitive to this. This can explain the LED flickering phenomenon. To solve this problem, several solutions are available, including Anti-error modules specially designed to smooth the electrical current: simple modules, double capacitors, or even with integrated relay and electronic board for the most sophisticated ones.

Your car bulbs may also flicker due to a bad contact. Make sure the connections are clean and secure. They should be tight enough to ensure proper current flow, even when the vehicle experiences vibrations (bad road, path). Generally, cleaning and tightening with pliers or a screwdriver is enough for the headlight to work properly again.

Flashes and flickering headlights on a German vehicle

You have just equipped a German vehicle with LED bulbs and you notice flashes and flickering for a few seconds when turning on the ignition. This is completely normal and will not cause any damage. It is not a LED failure or an installation error! This peculiarity is due to the onboard electronic system (multiplexing). German vehicles such as BMW, Mini, Volkswagen, Audi, Skoda are the most affected by this phenomenon.

The culprit for this inconvenience is the "Check control" bulb monitoring system, which activates for about ten seconds when the vehicle starts. The purpose of this advanced system is to warn you if the bulb is not working even before you start your journey. As a result, you will not take any risks on the road or risk getting a ticket.

The issue is that the electronic system is designed for installation with halogen bulbs. When you want to replace the old original bulbs with LEDs, some parameters change and affect the behavior of the monitoring system, especially with the appearance of LED flashes which are actually the visible manifestation of micro electrical pulses sent by the cabin computer (BSI) during the bulb testing phase.

With halogen bulbs, the light flashes are not visible because the light response times are much longer than with an LED. This allows an electric current to pass through with precise and ultra-fast timing, without even giving the halogen bulb filament time to light up. Conversely, an LED bulb lights up at the slightest stimulation, hence the appearance of light flashes at the headlights.

To reduce or eliminate this flickering headlight phenomenon, you can reprogram the lighting computer, even if this disadvantages the bulb monitoring system. Another solution is to add a high-end Anti-Flash-Bug module composed of a digital filter and a capacitor to smooth the current and thus drastically reduce or even eliminate the flashes. This solution benefits the bulb monitoring system, which will remain operational.

Change the vehicle's front LED headlight bulb

If the vehicle's headlight still flickers after all possible checks, you will need to change the bulb.

Remove the old LED bulb

To access the LED bulb, simply remove the headlight's sealing cover. The bulb is located in a bulb holder connected to a power connector. Fixed to the headlight, the bulb is usually held by a metal rod. To remove it, firmly hold the body of the LED by the base and turn it a quarter turn to unlock it. Then pull it towards the back of the headlight to extract it (some LEDs need to be unscrewed or just pulled back, depending on the LED's characteristics). Next, you just need to remove the LED ring lodged in the headlight opening. To do this, press the small metal rod above and shift it to the side to release and remove the ring. In other cases, you need to pull up or turn a quarter turn to unlock the ring's fastening system.

Install the new LED bulb

Before installing the new LED bulb, it is highly recommended to remove the ring first to coat the base and the LED's O-ring with a special gasket grease (temperature resistant and prevents swelling). Then, the LED will be perfectly mobile on its ring, which will make installation easier while greatly reducing the risk of headlight damage or damage to the LED itself.

Last recommendation before installation: quickly test the LED by connecting it outside the headlight without fixing it. This will allow you to ensure it works properly without committing to a major intervention if the test is not conclusive. For installation, simply follow the same steps as when removing the old LED, but this time in reverse order. When the new bulb is in place, reconnect the power wires, then test the new bulb by turning on the headlights. Some LEDs have reversed polarity on the connectors, if they do not work. Close the headlight with the sealing covers.

These are the different actions to take in the case of a flickering headlight. You can contact professionals in the field to purchase quality LEDs that are most suitable for your vehicle.