# Dimming/sporadically out HID headlight. How to tell if it's the bulb, ballast, or ignighter? **URL:** \ **Category:** Factual Questions\ **Created:** [July 4, 2015, 2:59pm UTC](https://boards.straightdope.com/t/dimming-sporadically-out-hid-headlight-how-to-tell-if-its-the-bulb-ballast-or-ignighter/724234 "2015-07-04T14:59:23Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Rhythmdvl](https://avatars.discourse-cdn.com/v4/letter/r/85f322/32.png) [@Rhythmdvl](https://boards.straightdope.com/u/Rhythmdvl)\ **Post date:** [July 4, 2015, 2:59pm UTC](https://boards.straightdope.com/t/dimming-sporadically-out-hid-headlight-how-to-tell-if-its-the-bulb-ballast-or-ignighter/724234/1 "2015-07-04T14:59:23Z")
1999 Acrua TL. The lowbeam of one headlamp is occasionally out. Turning the headlamps off then on again resuscitates them for a good while, but that’s going to stop working some day. Plus, when one is out it’s a magnet for getting pulled over. Bulbs are a hundred bucks (and come with stern warnings that holy shit I could _die_ from changing a bulb :eek: ), so I don’t want to willy-nilly change it if it’s a different part. Plus, you’re “supposed” to change them in pairs, so I don’t want to drop that kind of cabbage in the dark. Is there a relatively easy check if it’s the bulb or something else? Do the symptoms point to one more than an other? Thanks~ ---
**Author:** ![Leaffan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leaffan/32/299_2.png) [@Leaffan](https://boards.straightdope.com/u/Leaffan)\ **Post date:** [July 4, 2015, 3:17pm UTC](https://boards.straightdope.com/t/dimming-sporadically-out-hid-headlight-how-to-tell-if-its-the-bulb-ballast-or-ignighter/724234/2 "2015-07-04T15:17:31Z")
From [Wikipedia](https://en.wikipedia.org/wiki/High-intensity_discharge_lamp): > [@](#): > > At the end of life, many types of high-intensity discharge lamps exhibit a phenomenon known as cycling. These lamps can be started at a relatively low voltage. As they heat up during operation, however, the internal gas pressure within the arc tube rises and a higher voltage is required to maintain the arc discharge. As a lamp gets older, the voltage necessary to maintain the arc eventually rises to exceed the voltage provided by the electrical ballast. As the lamp heats to this point, the arc fails and the lamp goes out. Eventually, with the arc extinguished, the lamp cools down again, the gas pressure in the arc tube is reduced, and the ballast can once again cause the arc to strike. The effect of this is that the lamp glows for a while and then goes out, repeatedly. It sounds like it’s the bulb. How difficult is it to get to the bulbs? Could you easily swap the left one and right one and see if the symptom follows the bulb? (I would assume you shouldn’t be touching the glass on these things.) ---
**Author:** ![Rhythmdvl](https://avatars.discourse-cdn.com/v4/letter/r/85f322/32.png) [@Rhythmdvl](https://boards.straightdope.com/u/Rhythmdvl)\ **Post date:** [July 4, 2015, 3:31pm UTC](https://boards.straightdope.com/t/dimming-sporadically-out-hid-headlight-how-to-tell-if-its-the-bulb-ballast-or-ignighter/724234/3 "2015-07-04T15:31:43Z")
Holy cow, that fits exactly. I never would have thought to check Wiki for an answer like that, thanks! Will check on returnability—it takes a long time for it to go out (or for us to notice), so a simple swap might not show up right away (but will try nonetheless). ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [July 4, 2015, 9:18pm UTC](https://boards.straightdope.com/t/dimming-sporadically-out-hid-headlight-how-to-tell-if-its-the-bulb-ballast-or-ignighter/724234/4 "2015-07-04T21:18:04Z")
Headlight bulbs for a 1999 TL appear to be $5-16 or so online. Where are you getting 100? > **[Amazon.com: 99-10 00 01 Acura TL D2S D2R HID Headlight Light Bulbs Diamond White...](https://www.amazon.com/99-10-Acura-Headlight-Light-Diamond/dp/B004BCLBJM)** > > Buy 99-10 00 01 Acura TL D2S D2R HID Headlight Light Bulbs Diamond White 6000K: Headlight Bulbs - Amazon.com ✓ FREE DELIVERY possible on eligible purchases ---
**Author:** ![jz78817](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jz78817/32/1028_2.png) [@jz78817](https://boards.straightdope.com/u/jz78817)\ **Post date:** [July 4, 2015, 11:58pm UTC](https://boards.straightdope.com/t/dimming-sporadically-out-hid-headlight-how-to-tell-if-its-the-bulb-ballast-or-ignighter/724234/5 "2015-07-04T23:58:27Z")
> [@astro](#): > > Headlight bulbs for a 1999 TL appear to be $5-16 or so online. Where are you getting 100? > > [Amazon.com: 99-10 00 01 Acura TL D2S D2R HID Headlight Light Bulbs Diamond White 6000K : Automotive](http://www.amazon.com/99-10-Acura-Headlight-Light-Diamond/dp/B004BCLBJM) those things are trash. Aftermarket HID capsules (not from a reputable OE supplier) are to be avoided. at 6000K they’re going to be way too blue. the '99 TL takes a D2R capsule; a better choice would be Philips. OE color temperature and a reputable brand: > **[Amazon.com: Philips D2R Standard Authentic Xenon HID Headlight Bulb, 1 Pack :...](https://www.amazon.com/Philips-Standard-Authentic-Xenon-Headlight/dp/B00480J4KA)** > > Buy Philips D2R Standard Authentic Xenon HID Headlight Bulb, 1 Pack: Headlight Bulbs - Amazon.com ✓ FREE DELIVERY possible on eligible purchases