I have a 2008 Lexus is250. HID bulbs. I noticed yesterday sometimes both my headlights shut off but come back when I turn the lights on and off. Keep driving and sometimes the passenger bulb will go bad. Other times the driver side will be off and the passenger will be on. Sometimes I have no issues and both lights stay on.

Is there any way to confirm without swapping the bulbs? I've been looking for an excuse to buy VLAND led headlights and get rid of this possible problem all together at the sacrifice of the AFS. But if can find a fix without doing that I would prefer it. But I've also heard the new ballasts tend to not last either. Any ideas?

 

There is no practical way to test bulbs and ballasts when they are in the car need to do swap 'till you drop testing. HID tech was great at the time but in reality it is complex, draws a lot of power and doesn't last all that long.

 

Just got home from another night drive. The passenger light comes on dimmer than the driver side as well

 

Your best bet is to start with new good bulbs. OSRAM CBI or equivalent. Do not touch the glass as the oils will cause uneven temperature on the bulbs surface, causing it to fail.

IME D4S bulbs last about 4 years. I had some cheap ones in for a while ($60 pair) and they did what you describe. The OSRAM's are good bulbs. ~$180