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I've got Xenon headlights and my car has a feature which automatically turns the headlights on at night. Currently I'm hesitant to use the auto-on feature because the headlights turn on when I start the car in the garage or park in the garage.

I know flicking on/off lightbulbs harm them in general, and I don't want to burn out the expensive bulbs. However HID bulbs don't have filaments if I read correctly, so I don't know if they'll burn out for the same reason.

The headlights come on unnecessarily about twice a day if I enable the auto-headlight feature. Will this significantly impact the life of the bulbs?

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Yes, HID bulbs do not like excessive cycling, it causes damage to internal contacts as the arc is struck with high voltage. After striking and once a stable arc is formed, the voltage drops to around 40-80V. The bulb lifespan is still very long, even if you switch them multiple times per day.

HID bulbs do wear and burn out. Acceptable life span is between 5-10 years, depending on how much the lights are used. The first sign of failure is reduced light output, second is colour shift (colour of the light starts to shift to red/purple), third is flickering/random on-off cycling. If you see any of these symptoms then the bulb is due for replacement.

I have replaced HID bulbs twice in my life: once on a 13-year old Saab and once on a 2015 VW Golf. The Golf switches it's headlights every time you unlock the car, which contributes to bulb wear. The Saab had (mandatory in Europe) DRL function, where the lights would always turn on when you started the car and stayed on until you shut down the engine.

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I'm no expert, but I have the same setup in my car. I had to install a capacitor to give the HIDs constant power so they wouldn't get power at 60Hz. However, they do turn on and off once in a while, say going through a tunnel.

I haven't had a single issue with them in the last 2 years - since they were installed. As long as they have proper power when they're needed, I don't think it's a big deal.

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  • These are factory installed so I'm sure they're installed properly, just concerned about the longevity. The car's six years old but I'm not sure if the lights have been replaced.
    – Zelda
    Commented May 22, 2012 at 18:29
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    They shouldn't ever need to be replaced - in the lifespan of the car. That is one of the key benefits of HIDs - they don't get that thermal shock wear that ordinary bulbs get.
    – Rory Alsop
    Commented May 22, 2012 at 20:47
  • @RoryAlsop Hm, really? So my 6 year old bulbs should last quite a while still for example?
    – Zelda
    Commented Jun 4, 2012 at 20:38
  • Definitely! My garage was astonished I managed to kill one- turns out I caused it by damaging a casing that allowed water in, which then froze at minus twenty! £600 for a new one :(
    – Rory Alsop
    Commented Jun 4, 2012 at 20:47
  • My Audi needed a new pair at 100k (eleven years) at £600 each. UK roads may not have helped, as they ended up going out whenever the car went over a bump. However the Audi dealer said that 2006 xenons had that sort of lifespan, and even showed me a technical note.
    – Andrew Leach
    Commented Mar 28, 2019 at 21:17

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