Any suggestions on why these HID's won't come on?
 

stock headlights, HID's went out, 1 and then the other. when I replaced the bulbs, the new bulb came on and was working fine it seems just until I put the other one in. both ceased to work at that point, even if I took it out again.
fogs and everything else are fine
1 ballast is a recent replacement and only a year old.
bulbs - new
swapped relays behind the battery to no avail
found a pretty badly corroded battery wire on the positive terminal, so I chopped and replaced it but not sure how far down the corrosion goes.
is there anything else I should try?