Question 1

When bulbs need replacing

Accepted Answer

Headlights are a critical safety feature — a non-working headlamp reduces visibility in the dark and can lead to MOT failure. Bulbs should therefore be checked regularly, and particularly before long trips. Rear lights and brake lights are also required by law and their operation is tested during the MOT.

Conventional halogen bulb life is 500–1 000 hours, around 1–2 years in normal use. They usually fail quickly — one moment the lights are bright and the next they've gone. Xenon and LED lights last much longer (5 000–10 000 hours), but when they fail they can change colour (xenon goes reddish) or flicker before going out.

Replacement difficulty has grown considerably — on a modern car changing a bulb may involve removing the bumper or handling a separate light control unit. LED and xenon lights require the manufacturer's designed control unit, and replacing them requires a trained technician and the right tools.

Question 2

How bulb replacement is done

Accepted Answer

In the simplest case a bulb is changed by opening the bonnet and removing the rubber cover, electrical connector and retainer from the old bulb. The new bulb is fitted in place without touching the glass with bare fingers — grease causes premature failure. This job is quick and takes only a few minutes.

On modern cars — especially German premium vehicles — the entire headlight may need to come out. To reach the bulb, the bumper, wheel-arch liner or whole front panel has to be removed. This takes 30–60 minutes and requires several tools. Some cars have a separate service hatch, but this is less common on newer vehicles.

LED and xenon bulbs additionally have a high-voltage control unit (ballast) that steps the car's 12 V up to the required higher voltage. If the ballast is faulty, replacing the bulb doesn't help — the fault is in the electronics. We diagnose these via the diagnostic tool and an oscilloscope. After replacement we always check beam aim against a headlamp alignment screen so the lights don't dazzle oncoming drivers.

Question 3

Why do bulbs keep blowing?

Accepted Answer

If a bulb blows again quickly after replacement, there's usually an underlying fault code in the system. Most commonly it's voltage load: the charging system occasionally delivers over 14.5 V, which destroys halogen bulbs much faster. This is measured with a multimeter on a running car and the charging regulator checked. Another common cause is a poor earth: a corroded or loose ground cable raises the voltage across the bulb to abnormal levels. Grease on the bulb glass at installation is also a surprisingly common cause of short life — grease causes uneven heating in hot spots and the glass shatters after just a few uses. A quality manufacturer (Osram, Philips) always lasts longer than a copy product, with the difference showing after the first six months.

Bulb Replacement in Vantaa