Xenon light is High Intensity Discharge lamp (HID), it light up through the process of powering up the noble gas such as Xenon in the quartz tube to 20000 volt via the car 12v ballast. The Xenon gas ionize and produce electric arc between the electrode, make the bulb light up. As the usage time increase on the bulb, insufficient noble gas causing weakening light and it can differentiate by eyes that the brightness, colour and start up speed on both headlamp is different.
Suggest to repair at workshop during daytime when the environment light is good.
1. Visual check the left and right headlamp if the colour shifted, inconsistent start up time, water going in, or there is big difference in the brightness of both lamp.
2. Use headlamp diagnose device to check the headlamp.
3. Replace the faulty light bulb.
4. Usually the Xenon light are replace in pair even if only single unit is faulty in order to keep the consistency.