Correct me if I am wrong but doesn't the Vanner provide 12v of power from the 24v batteries to the 12v headlights and other 12v accessories. I have 12v headlights and the bus had a 12v paging system and a 12V radio which have since been removed.
Properly connected, an equalizer "equalizes." Meaning it keeps the two "halves" of a 24-volt battery system in balance. This is important if you have 12-volt loads connected to the center tap of the 24-volt system, because otherwise the "lower" battery will tend to be undercharged and the "upper" battery will tend to be overcharged.
So, no, it's role is not to "provide 12v of power." It's role is to keep the batteries healthy when 12 volt power is being drawn from them.
That being said, it is possible to connect a Vanner equalizer in such a manner that it is, effectively, a 24-to-12 volt converter, by connecting the 24-volt side to the batteries, and the 12-volt side to the load. Note that, in this mode, you typically need a much larger Vanner model than if you connect it to the batteries instead.
BTW, 12-volt headlights are often bridged across the 24-volt battery bank in such a way that an equalizer is not necessary (one headlight across the lower battery, one across the upper). This is the way MCI headlights are connected, for example.