i would check your ballast and your wiring harness too. make sure there are no signs of moisture damage or exposed wires, rubbing or fraying. if something is wet or shorting out somehow your ballast could have a safety feature to automatically turn off so as not to cause any damage. checking the fuse in your ballast wouldn't hurt either. your endcaps can be cleaned with steel wool or a wire brush, but if there's no signs of corrosion on them then they're probably alright. you can also check to make sure that all of your wiring is still firmly seated/crimped/connected into your endcaps as well, and that there's no exposed metal between the coating on the wires and the endcaps.
