In Reply to: are they supposed to yellow all the way??? posted by Eddie M on October 17, 2001 at 16:13:08:
Once it get to white, it is supposed to supply constant energy... so if insufficient, then it will turn yellow.
You can test your bulb by hooking it up to your newer ballast if the electrical socket fit... and I bet you the bulb will stay white. I don't know what the difference of the ballast is but check with your supplier before testing it.
I recall a case where i discussed with a MB owner who said his HID went yellow... and he said the dealer changed the bulb... and it is still yellow... finally, new ballast, and white again.