73pikefiretruck

for a 73 cf-600 fire truck are the batteries soposed to be wired (series for 24v) or (parallel for 12 vlots)

Our fraternity (PIKE) just bought a firetruck which is a 73 CF-600. Having problems with the charging system. Showing 24 volts by the way the batteries are wired up currently Which is series. From all the bulbs and electrical stuff on the truck is it not soposed to be 12 volts? Which would make since why most of the bulbs are blown. Can i get a diagram Also is there any kind of service manuals or where i can get any basic info on this truck? Thanks, Jesse