Looking at that diagram, the 50A breaker only feeds the 20A breaker.
The 20A breaker feeds:
- The black wire feeds the neutral safety switch and the starter solenoid.
- The green wire feeds the fuel control and the hi-temp/lo-oil buzzer.
- Then you have the yellow wire.... YIKES! That feeds pretty much everything else.
Here's how I troubleshoot everything:
This works for pretty much everything. Software, hardware, mechanical devices, electrical devices, etc....
- Cut it in half.
- That determines which half the problem is in.
- Reconnect the problem half.
- Cut the problem half in half.
- Repeat.
- Keep cutting the problem in half until you isolate it.
I'd disconnect that yellow wire at the ignition switch and see if that kills the problem first. It appears none of that stuff is needed to start the machine. It's just lights, gauges, draft control, PTO solenoid, tilt seat, fuel gauge sending unit, oil temp and pressure sending units, and the hydraulic cooling fan.
If the problem persists, the problem is in the upper half of the diagram, which appears to be the fuel control and starter solenoid.
But I'll guess that switching your 15A breaker back to the 20A that its supposed to be may resolve it.
Anyhow, you get the gist.... cut it in half, observe, reconnect, cut, reconnect, cut, etc... until you get it down to the problem component.