Why you need to replace old HID headlight bulbs

Once desirable fifteen years ago, High-Intensity Discharge lamps are falling out of favour, as LED headlights have improved and become more widespread.

You may have heard about these lamps being equipped with 'Xenon HID bulbs'. 'Xenon' refers to just one of the gases used within the HID bulb and is a word that marketing professionals overuse. You can buy Xenon-branded filament bulbs, for instance! Again, this tends to refer to one of the gases used within the bulb to enhance light output.

Even so, plenty of cars on UK roads utilise genuine Xenon HID headlights, although GEM has fielded complaints about them not working properly and affecting safety. So, how can this be?

How long do HID bulbs last?

Unlike halogen bulbs, HIDs deteriorate gradually, before failing. Research conducted by the Leeds-based RING Automotive  shows that HID light output reduces and the colour changes as the bulb gets older. This is caused not just by the molecules of gases and salts inside ageing but they also defuse progressively through the glass.

As the light deterioration is gradual, the average owner tends not to notice that the headlights are becoming weaker, especially if the car achieves an MOT Test pass. RING advises, therefore, that the HID bulbs of both headlights be replaced every five years.

Pros of HID headlight bulbs

The main advantage is superior visibility for the occupant. Additionally, the bulbs can last several times longer than filament bulbs. They are also more energy-efficient and produce less wasteful heat.

Disadvantages of HID Headlight Bulbs

Despite the impressive light levels, even new HID bulbs require several seconds to warm up. This is why separate HID bulbs are not to be used for main beam purposes.

They are also more complicated. Additional electronics are required to regulate their power supply and the headlamp must incorporate self-levelling and a wash facility to reduce the risk of dazzling oncoming motorists.

What to do about worn-out headlights

HID output can be reduced to such an extent that the driver might not notice that visibility has been compromised severely. They are also not as straightforward to change, either.

Due to them 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. Some professionals even insist 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, or a capable DIYer, should be able to replace HID bulbs. This video  provides a general overview of the procedure.

Advances in Automotive Lighting Technology

Modern lighting has become increasingly sophisticated. Should a dashboard warning indicate a problem with the headlamp self-levelling mechanism, contact a garage. However, you should be able to replace filament and HID bulbs yourself, if you are confident. As an aside, LED headlight bulbs cannot be changed, because they are part of the moulded lamp unit that cannot be accessed.

While less common these days, never buy illegal conversion kits that permit you to fit HID burners into halogen headlamp housings. These are still available through online marketplaces and would cause an MOT Test failure. Fitting LED conversion kits is also not permitted for modern cars.

Keep up to date with GEM Motoring Assist at:

Twitter: @motoringassist

Facebook: @gemmotoringassist

Instagram: @gem_motoringassist

LinkedIn: @gem-motoring-assist-limited

Share this on socials below: