Yes the back of the HD Service manual has detail schematic diagrams that fold out and have anything you'd want to know. I think they run around $60 retails but I got mine from a dealer on ebay alittle cheaper. Part number for your 08 would be 99482-08.
And it's a huge book, 1.5 inches plus!! Full of great info: Pulling tank, changing fuel pump, tire/rim work, all fluids, plugs, lighting harness and bulbs, engine internals, EFI, clutch, cables, and a bunch more. It was 99482-08A, for my FXSTC 2008. Wiring diagrams in the back. $60.