battery not charging at all

I have a Craftsman lawn tractor model 917.258681 with a Kohler Magnum engine, 19.5HP twin. My volt meter shows absolutely no charge going to the battery. I have no schematic for the electrical system on this tractor, but if it is like many other mowers, I would look for a rectifier between the engine and the battery, but just don't know where to start looking for it since in the past I have also seen the rectifier in line with wires and covered with shrink tube, which makes it almost impossible to see or find.

I would much appreciate any help.

could you also tell me where I can find a schematic and parts manual for this tractor?