Car headlight help

[Pittenger5]

Trying to help a wifes friend, she has an older BMW 7series that has an HID conversion done to it. One headlight doesnt work, she says if the car sits overnight or something and she turns them on it works, if she drives at all then turns it on it flickers and then shuts off. I checked the wiring quick, and it looks clean and secure. Any other suggestions?

[NobodySpecific]

Wild guess: could the ballast be failing at the higher voltages (versus turning on with a somewhat stable and/or lower voltage either before or while starting)? Or the ballast could be overheated by the engine and fail to turn on. Turning on is the hardest time for the ballast since that is when it generates a high enough voltage to get the gas to generate light, which is significantly higher than the voltage required to maintain the light.

[aldend123]

Sounds like a bad ballast. Swap it to the other side, see if the problem "follows" it. If it does, replace it.

[golden chicken]

^^or swap the bulbs around.