So it blows the fuse without starting the engine - running or starter turning? correct?, just putting the key into the on position?
Start by isolating some components like the starter, pto, charging system until it stops blowing the fuse, then you can proceed with checking for the shorts.
1. ) Check stator for short to ground.
2.) Check starter /solenoid for short. (stuck in a position that wants current, lots of current
3.) Check coil(s) for short/damaged - resistance readings
4.) Check all switches for shorts. These may be
5.) Check safety interlock electronics for short or blown items
Yes, its blows a fuse when the key goes to the on position. So I went through and disconnected each item one by one: ignition coil, stator, starter, seat switch, PTO switch, RIS switch, and finally the neutral start switch (NSS). Finally the fuse did not blow when I disconnected the NSS.
I tested the NSS and found continuity between terminals when it's in neutral, no continuity in all other gears. The repair manual is difficult to understand , I think the switch is functioning correct but the description in the manual seems to say otherwise. Here's what the repair manual says: " If there is continuity between the terminals when the transaxle is in neutral, check transaxle linkage adjustment, switch installation and repeat test procedure. If the switch fails, replace"
I also tested the ignition switch according to the repair manual and it doesn't show continuity between the terminals as required by the test (see attached image). Terminal A-B and D-E have no continuity in the Run position. Terminal A-B have no continuity in the start position.
I'm thinking the problem is in the ignition switch, not the NSS.