A broken car bulb is annoying in itself. It is really annoying, however, if the replacement does not fit or otherwise causes problems. The reason may be one of the following errors.

Incorrect type: Some names are similar. For example, there is the widespread H4 headlamp, but the rarer HB4 is quite different. It has a different socket, a different port, and only one filament, while the H4 has two. In short: a purchase of this kind cannot be installed. The situation is similar with signal bulbs for turn signals, brake lights, and taillights: a P5W and W5W cannot be interchanged. So: the name must be one hundred percent correct.

Incorrect voltage: It is not unusual, especially in truck stops along the highway, that a 24 V bulb is reached for in the rush of purchasing. That is dead right for users of a commercial vehicle. But for passenger cars designed for 12 V, it only provides a dim light.

Incorrect output: Fortunately, there are only a few bulbs that have the same base but a different output. These include the W5W and W3W types. The numbers in the names refer to the output. A W5W in instrument lighting may overheat the instrument if it is designed for W3W. On the other hand, the license plate illumination lights will not be bright enough with the three-watt version.

Incorrect positioning: Light bulbs only fit into the headlight in one position. In theory, that is, because with the use of force a lot can go wrong, leaving the light sources hanging askew. And wrongly positioned lights often dazzle oncoming traffic. So never use force! The instruction manual shows the correct position, which can, by the way, also be noted when removing the old bulb.

You can’t do anything wrong with top brand bulbs – not with the exact right model and an accurate installation.


Incorrect brand: There are large differences in quality between automotive bulbs. Not only the correct wattage or the correct name – for example H7 – counts. OSRAM fits the filament for each single halogen bulb into the socket individually. That way, later on, the light distribution on the road will also be correct.

Incorrect handling: Car bulbs don’t like it when the glass parts are touched by your fingers. Hand sweat, grease, or cream, together with heat, can damage the glass and parts of the headlamp. If touching the glass bulb is an absolute necessity, using a clean tissue can prevent skin contact and thus damage.

Incorrect paint: Unprofessionally colored bulbs have become rare. From time to time, however, halogen bulbs dipped in blue paint still appear. In the headlight, the paint usually burns off quite soon. Then, not only is the beautiful appearance gone, but the headlight is often permanently damaged, too. On the other hand, there is no danger present with turn signal bulbs from branded manufacturers that have been painted yellow with special heat-resistant paint. And OSRAM also has bluish bulbs on offer. Of course, the high-quality Cool Blue coating also does no harm.

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