I've got a late Rover 75 CDTi with Xenon dipped headlights.
The handbook says not to change these yourself, as they use high voltages and could be seriously harmful.
Having to go to a garage to get a bulb changed is ridiculous. Anyone got any experience iof doing it themselves? Is there a particular process to follow?
Has anyone got Halfords to do it as part of their "We'll fit it" service?
Xenon bulbs are a form of short-arc lamp and as such the car's circuit has ballasts (think of the fluorescent tube in your kitchen) built in to supply the incredibly high starting voltages required to establish the arc. These bulbs require a starting pulse, maybe 10 or possibly 12 kV. The ballasts can produce starting pulse voltages around 18 - 20 kV. These starting pulses must be repeated frequently until the arc is established. Also, the ballast must supply an open circuit output voltage - other than the starting pulses - of over 300 volts to force the arc to establish.
The voltage across the lamp is normally around 80-90 volts when it is warmed up.
They also get hot, very hot. The internal quartz arc tube temperature is probably typically around 800 degrees C. The surface temperature is not this hot, but it is definitely not anything you'd want to touch. The arc tube always has at least some minuscule risk of exploding and should only be operated within it's headlight housing.
The bulb must be clean and free of dirt, grease, organic matter, ash, salt, or alkali. Salts, ash, and alkalis have a tendency to slowly leach into red-hot and nearly red hot quartz which will result in strains, weak spots, and maybe cracks.
Basically, ensure the lights are switched off (and haven't been switched on for a while, overnight to be sure there's no residual charge left), don't touch any contacts or the glass and be careful. I've replaced them on a friends Audi and I'm still here to type this.
Andy J.
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.