Your headlight bulb burns out, you pop the hood and realise you don't know which type you need, or whether you can drop in that LED your neighbour keeps praising. The question matters even more if your safety inspection is coming up, because the wrong bulb can fail the car even when everything else is perfect. Here's how not to get lost in the H1, H4, H7 labels, and what the rules in BiH really say about LED.
How to identify which bulb your car uses
The easiest way is to check the owner's manual, usually in the chapter on bulb maintenance. It clearly states which type goes in the main headlight, which in the fog lamp, and which in the rear lights. If you don't have the manual, pull out the existing bulb and read the marking on the metal part or on the glass at the base.
The types you'll most often run into in BiH on European models are H1, H4, H7, H11, HB3 and HB4. H1 is often used for high beam on older cars. H4 was the standard for cheaper and older models for a long time, because a single bulb carries both low and high beam. H7 is today the most common for low beam on most European cars from the early 2000s onward. H11 turns up in fog lamps and as low beam on newer models, while HB3 and HB4 are more common on models with Asian and American origins.
The key thing to remember is that H4 and H7 are not interchangeable. They have a different base, a different number of contacts and a different filament layout. If the base doesn't seat easily, you haven't found the right type - don't force it.
H4 and H7, the difference in practice
The H4 bulb has a double filament inside one glass envelope. One filament gives low beam, the other high beam, and both run from the same bulb. That's why the H4 has three contacts at the base. When it burns out, usually only one filament goes, so for example your high beam works but the low beam doesn't.
H7 has only one filament, one beam, and two contacts. A car that uses H7 has a separate bulb for low and a separate one for high beam, which means each headlight will hold two bulbs. That's why on newer cars you sometimes change four bulbs at once, and on older H4 cars only two.
Halogen, xenon or LED, what's legal to fit
The main rule that applies in BiH is ECE, that is UNECE homologation. It's the European standard for lighting equipment and you'll recognise it by the letter E with a number inside a circle, stamped on the glass or on the metal part of the bulb. Without that marking the bulb is for the garage, not the road, and the safety inspection rightly fails it.
Halogen bulbs from trusted brands like Osram, Philips and Narva come with the ECE marking and pass without trouble. That's still the safest choice for a standard headlight that was factory-designed for halogen.
Xenon, that is HID, is found mostly on more expensive German models. Factory xenon is legal because it comes as a package with a projector lens, a controller, automatic beam levelling and headlight washers. Retrofitting xenon into a headlight that wasn't designed for it doesn't comply with the rules and fails the inspection.
LED is legal only when the entire headlight assembly, with lens and controller, is factory homologated for an LED light source. That means a car that rolled off the production line with LED headlights. Everything else is the subject of the next section.
Why retrofit LED H7 fails the safety inspection
At the shop we regularly see drivers who buy the "brightest" LED H7 or H4 bulbs online, fit them themselves, and then fail the safety inspection. The reason isn't the inspector being mean - it's physics.
A halogen headlight has a reflector and lens that were factory-designed around the exact point where the halogen filament glows. When you drop an LED chip into that base, the light source is no longer in the same place and isn't the same geometry. The beam scatters, the upper cut-off line of the low beam is no longer sharp, and part of the light shines into the eyes of oncoming drivers. The beam tester at the safety inspection shows this immediately and the car fails.
On top of that, retrofit LED kits usually have no ECE homologation for use in a halogen headlight. Without that paperwork the bulb is illegal, however nice it looks to the eye. Our recommendation is simple. If your car came from the factory with a halogen headlight, stick with a quality halogen bulb with an ECE marking. LED for fog lamps, the licence plate and the interior is as a rule no problem at inspection, but low and high beam are not the place for experiments.
How to change a bulb yourself, and common mistakes
The biggest mistake is touching the glass part of the new bulb with bare fingers. The oil from your skin stays on the glass, that spot heats up during operation and the bulb burns out fast, sometimes in a week or two. Always hold the bulb by the metal part or through a clean cloth. If you accidentally touched it, wipe the glass with alcohol and let it dry.
The second rule is to change headlight bulbs in pairs. Left and right have burned for roughly the same number of hours, so if one is gone, the other is very close to the end. If you change only one, the beam from the two bulbs won't be the same colour or the same intensity, and within a few weeks you're back to change the other.
Before you start, get gloves and a clean cloth ready, switch off the engine and wait for the old bulb to cool down. Pull off the rubber or plastic cover at the back of the headlight, disconnect the connector, release the wire clip or unscrew the ring that holds the bulb. Insert the new bulb so the notches on the base seat into the slots in the reflector, put the clip, connector and cover back. Check that both lights work before you close the bonnet.
A special note for owners of cars where the bulb is changed through the wheel arch or through an opening that barely fits a hand. On some Renault, Ford and Opel models the H7 base is so cramped that the bulb is changed by feel. If it won't go, don't break the plastic - come to the shop.
Hazy headlight lenses, polish or replace
Yellow and cloudy headlight lenses aren't just ugly, they seriously cut beam reach, in some cases by as much as forty percent. The headlight shines normally on the inside, but the light is lost and scattered on the damaged coating.
Polishing with a headlight paste is a good fix for mild to moderate damage, when the lens is hazy but without deep cracks. After polishing a protective coating must be applied, otherwise the lens hazes over again within a few months.
If the lens is cracked, has stone-chip pitting or the coating has completely peeled off, polishing won't deliver results and it's fair to go straight to replacing the whole headlight. A misaligned or damaged headlight fails the safety inspection just like the wrong bulb, so whenever you change a bulb, unload the boot or pick the car up from a service, it's worth also checking the beam height.
If you're not sure which type of bulb you have or suspect that your beam has dropped, drop by the shop before you head off to the inspection. Five minutes of checking saves you a second trip to the lane.