Hi allgun,
Not sure of your electrical skill level or if you have a multimeter, but get a bunch of 20 amp fuses.
Possible problem areas:
The fuse holder itself.
Chaffing of the electrical harness somewhere on the machine or engine.
Key switch.
PTO switch.
Engine fuel shutoff solenoid.
Electronic control module.
All electrical connectors, corrosion, poor contact, burning of contacts or melting of plastic connectors.
When key on, power goes to the PTO switch, the seat switch, the safety circuits starting with the brake interlock switch, the L/H then R/H control lever switches. The power from both the seat switch and safety control circuits go to the electronic control module.
There are two diodes in the electrical system, both of which are in the cranking circuit. One is actually inside the cranking relay, the other is installed in the electrical harness.
I would start trouble shooting by disconnecting the engine harness connector and try key on and work your way back thru the electrical system toward the keyswitch.
I print enlarged parts of the electrical system diagram and piece them together so I can see them easier and get a better understanding of the system before I start diagnosing an electrical system. As I do this, I also make a list of the wire colors and to which components or circuits that they are related to.
Enjoy!!
Mad Mackie in CT:laughing::biggrin::smile:
On this forum, there is a Scag group where you can post and possibly get specific responses relative to Scag machines. Posting your machine model, serial number and engine make/type, helps other members target more specific comments about your machine. On the Scag website there is a link to manuals, but you need the model and S/N of your machine to get the correct manual, it is a printable pdf download and periodically updated by Scag.