Xenon head­lights

Ev­ery­thing you al­ways wanted to know about ve­hi­cles but were afraid to ask

Townsville Bulletin - - Saturday Television -

NCE the pre­serve of top-end mod­els, so­called xenon head­lights are be­com­ing in­creas­ingly com­mon on vol­ume cars. Be­cause they are brighter and il­lu­mi­nate a wider area than con­ven­tional head­lights it has been ar­gued that they im­prove road safety. The term xenon is, tech­ni­cally, in­cor­rect.The lights are high-in­ten­sity dis­charge lamps (HID).They emit a bright, white light that is eas­ily dis­tin­guish­able from the yel­lowy halo­gen bulbs used on most cars. The term xenon be­came com­monly used be­cause xenon is added as a firestarter the other gases in the head­lamp take time to re­act, so it is the xenon that pro­vides the ini­tial flash when the lights are turned on. The av­er­age HID lamp pro­duces about 3,000 lu­men from 42 watts of power while a halo­gen unit will give up to 2100 lu­men from 65 watts.The stronger light means that xenon head­lamps can be smaller — aes­thet­i­cally more pleas­ing for most car de­signs — but are more ex­pen­sive. One of the prob­lems with HID lamps is that the dif­fer­ence be­tween the il­lu­mi­nated ar­eas of the beam and the dark­ness be­yond is pro­nounced, while con­ven­tional head­lamps of­fer a more nat­u­ral shaded edge. The only way to con­vert from halo­gen to HID light­ing is to re­place the en­tire as­sem­bly, in­clud­ing the front glass, fil­ters and lenses, with an HID unit.Af­ter­mar­ket kits are of vary­ing qual­ity, how­ever.They are ex­pen­sive and re­quire fit­ting and ad­just­ing by a pro­fes­sional to avoid prob­lems with badly aligned lights that dazzle on­com­ing driv­ers. Be­cause HID lights con­tain a mix of gas and met­als, bro­ken xenon units are clas­si­fied as spe­cial waste and must be dis­posed of cor­rectly. Bi-xenon head­lights use a sin­gle xenon lamp to pro­duce both the main and dipped beam.The full light out­put is used for the main beam and a shut­ter blocks off part of the light when a dipped beam is re­quired.

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