No bulb lasts forever. At some point they all burn out. But there are also other reasons why they stop working. Sometimes you can control the causes and postpone the replacement.
Normally, this is how the end of a lamp’s life comes about: over time a little bit of tungsten continually evaporates from the filament. Hardly surprising, because it has a temperature of several thousand Fahrenheit. This makes the wire thinner. One day, it’ll be thinned out so much that it’ll melt through. The lamp goes out.
The filament and the wire it’s made of are sensitive parts. One look with a magnifying glass will show how thin it is. Depending on the output, the tungsten wire is only a few hundredths of a millimeter “thick”. The smaller the output, in other words the fewer watts a lamp has, the thinner it is. Even though the metal is extremely durable, it won’t withstand all loads. In extreme cases, excessive shock makes the filament swing so much that it tears. A classic example is the number plate lights on station wagons. If you don’t close the tailgate gently but rather forcefully, you put a high load on the lamps. This applies in particular to C5W festoons.
Constant vibrations aren’t good for lamps either. Clattering motorcycles and shaky commercial vehicles can sometimes prompt the premature end of a filament.
One thing that has nothing to do with the illuminated part of a lamp is a problem with the base, with the most common one being corrosion – a problem familiar to many drivers. A small nudge of the lamp will make it light up again, but unfortunately not permanently. Rust, verdigris and other deposits must be removed. When the base of a lamp gets to a stage where it’s a nice shade of green, it’s best to replace it. But make sure to clean the holder beforehand. For persistent cases fine sandpaper will help. Sometimes a bit of alcohol and a cloth are enough. But never use contact spray. It’ll cause the metals to react again after a short time. Good contact grease won’t do any harm, on the other hand.
One thing that’s really annoying is when recently replaced lamps fail. When removing the lamp, you notice the inside of the bulb is white. To blame is what is called air leakage. The glass bit wasn’t closed off properly during production, so this effect tends to crop up with cheap no-name products. In lamps from Osram there’s pretty much no air leakage because of the precise, automated production and numerous checks. The manufacturer’s guarantee provides additional security.
But even high-quality products can’t perform miracles because there are physical limits. That’s why high-performance lamps such as the Night Breaker series have a shorter lifetime. Instead they bring more light to the road. Brighter light means hotter filaments and therefore more evaporating tungsten. At the other high end of the lifetime scale are the long-life lamps. They can be installed in rear lights for instance, which will give car owners peace of mind for several years.
Those of you who love your cars but not broken lamps, should still close the trunk gently.