Why you need to replace old HID headlight bulbs

Posted on December 4th, 2018 by Rob Marshall

Why you need to replace old HID headlight bulbs 

One of the many advantages with High Intensity Discharge lamps, as opposed to filament bulbs, is that they last longer – or so we thought. As more cars have been equipped with them from new, it has been noticed that, while HIDs do not fail suddenly like a traditional filament light bulb, their output diminishes with time.


Research conducted within the lighting department of Leeds-based Ring Automotive shows that HID light output reduces and the colour changes as it ages, caused by the molecules of gases and salts inside not only ageing themselves but also by defusing gradually through the glass. The image used with this blog shows the beam pattern of a new HID bulb (top), against the reduced output of the same bulb that is four years’ old.


As the deterioration in light output is gradual, the average owner tends not to notice that the headlights are becoming weaker, especially as a car is still likely to pass its MOT Test. RING advises, therefore, that the HID bulbs of both headlights are replaced every five years.


Fitting the bulbs

Due to them not only requiring very high voltages to operate and being more sophisticated than traditional filament bulbs, even some well established garages are reluctant to change HID bulbs, with some professionals insisting that this is a task for main dealers only.


RING insists that this is not true and, provided that the relevant safety advice is followed, an independent repairer should be able to replace HID bulbs. This video provides a general overview of the procedure.