hello fellows, i bought some D4s bulb from one of our vendor 2 years ago. for the last 4 months every time i would drive my car at night with the low beam on, one of the light will go off, its the passenger side. I would turn off my lights and it will turn back on again. What seems to be the problem, this happen most of the time when i turn. I would notice the that i have a bright yellow light on the right side and i know that my low beam is off, because of my fog. thnx for the input...

 

EIther the factory ballast is going bad or the bulb is is slowly dying.

Try swapping the D4S bulbs around and see if the problem persists on the same side, if it does either your factory harness or ballast is going bad, if it changes over you have a bad bulb.

 

I am having the exact same problem as you. Just recently replaced my factory hid bulbs with 6000k aftermarket. I will be doing the swap today or tmr.. and find out what the deal is..