Headlight Help Needed

Long time lurker, first time poster here. Great forum, I appreciate your unbiased opinions, saved me from wasting a bunch of money on junk lights.

Anyway, my question is only tangentially related to lights, hope you can help.

The vehicle is a 2000 Audi A6 with xenon low beams. Left lamp went out recently and I replaced both as they were original. Used OEM Osram bulbs from a reputable Audi supplier.

Unfortunately, the left lamp is still intermittent. It comes on when I turn them on but then goes out shortly thereafter. It will come back on if I cycle the switch but quickly goes out again. I checked for a bad bulb by swapping the bulbs LxR, problem stayed on the left.

Any ideas of what the problem might be?

Thanks for your help.

PJorgen said:

The vehicle is a 2000 Audi A6 with xenon low beams. Left lamp went out recently and I replaced both as they were original. Used OEM Osram bulbs from a reputable Audi supplier.

Unfortunately, the left lamp is still intermittent.

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Failing ballast or an intermittent open short, possibly.

Yep, Alaric's got it right: could be a faulty ballast, could be a wiring or connection fault. Beware of counterfeit parts, and make sure the headlamps are aimed correctly with an optical aiming machine.

Thanks for the input. I've gone over the wiring as best I can, checked continuity wherever possible - all seems OK. Will definitely look into the ballast next. Genuine Audi ballast is $$$, have seen cheaper but they're probably fake so will avoid those.

The headlights have an auto-aiming function which is still operable, it checks itself every time I turn on the lights; i see the beam move up and down. Is it reasonable to trust that this mechanism is aiming the lights correctly? FWIW, I don't get flashed by oncoming cars.

The headlamp levelling system cannot attain correct aim, no. All it can do is respond to vehicle loading conditions to maintain the basic aim setting that a human being has dialled in -- whether that setting is right or wrong.

I don't get flashed by oncoming cars.

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Has no bearing on weather your lamps are aimed correctly.

whether that setting is right or wrong.

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Though at this point in time i just assume that 99% of the vehicles on the road have incorrectly aimed headlamps... Especially all the rigs up here with JW speaker sealed beams aimed at the treetops....

PJorgen said:

The headlights have an auto-aiming function which is still operable

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And like -Virgil- said, they only adjust the beam relative to the aim it has-- so if they're misaimed, it'll help preserve that degree of misaim despite loading conditions.

FWIW, I don't get flashed by oncoming cars.

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Which is worth about $0.00

PJorgen said:

Unfortunately, the left lamp is still intermittent. It comes on when I turn them on but then goes out shortly thereafter. It will come back on if I cycle the switch but quickly goes out again. I checked for a bad bulb by swapping the bulbs LxR, problem stayed on the left.

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Try swapping the ballast ONLY, does the problem still stay on the left side? if so its a wiring or grounding problem if the problem moves, its the ballast. The best place to find an authentic ballast at a good price is to buy used online or a junk yard.

it may not be that easy, oem ballasts are usually build into the light housing.

alpg88 said:

it may not be that easy, oem ballasts are usually build into the light housing.

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You might be right but usually they are mounted to the exterior of the assembly and bolted or held in place.

A 2000 might need new headlamps anyway, seeing as the reflectors and the lenses may have degraded quite a bit by now.