As I was leaving work last evening, a friend yelled "hey, your right headlight is out". So I flicked it to high beam (it was on low) and high beam doesn't work either! I have a question about troubleshooting. (1) Isn't it unlikely that both bulbs would blow at the same time or is that a common failure mode? Since the low HID bulb has its own power source (ballast) and (I assume) the more standard-type high beam bulb its own source, what other things/circuitry might the two bulbs have in common to cause both to fail simultaneously? Also (ok I its two questions), whats the best way to troubleshoot the ballast and/or ignitor?

 

check the fuse boxes for headlight power
there may be a few

swap the hi beams left to right because its easy= see if that works

 

x2..


If they were working fine at once, and both didn't work at once, sounds like a fuse to me.

 

I think headlights are normally on a single fuse, so if that were the failure neither side would work. I will be swapping right side bulbs to left side tomorrow to eliminate failure of both bulbs as the cause. I am still hoping for any other explanations/ causes that would cause failure of both lights on one side while allowing both beams on the other side to work.