One of my retrofitted HIDs have been on a slow decline. At stoplights when the RPM got low enough, the driver side light would shut off. I couldn't really diagnose it until it finally gave out 100% now. Have any tips on figuring out the real cause behind the failure?

I've done this so far:
- check the 15a fuses (result: functional)
- check the voltage just before the ballast (result: 11.10v)
- check the voltage between the ballast and the bulb (result: 0.0v)

Now my question is do ballasts know there is no bulb connected and cease output? I had 3 compatible ballasts I tried it with and they all gave the same zero-output. (I can't verify they are working, however, they were in my old-crap-parts-bin).

What's next? Thanks