My 23CII did not come with a power box as this one does, so everything else may be different too.
The 'White Lite' switch removes all the filters from the lamp path to the mixing box. If the switch is inoperative it means you cannot remove filtertation other than dialing the knobs to zero. No big deal in itself but it could have a bearing on the dialing in or out of filters. My white lite filter lever, while not broken is sloppy in removing all filtertation 100%.
The use of this switch is in focusing and composing, where you want as bright an image as you can get. Once composed and focused I do not use the switch. For split filter printing I cover the lens with a cardboard and dial in and out filtration with the lamp on. There is no other way I know of.