okay just came in from bus
On our bus there is a solenoid on the panel by driver(open door outside)
when you turn the key to the "run" position it should activate("click")
this powers up the 12v side of the bus, things like alternator and fuel shutoff solenoid
When you turn the key to the "start" position it sends 12v to the starter solenoid (shiny gold-ish thing on top of the starter)
this makes the starter spin to start the engine
So I noticed on mine (while getting you pics...thanks!..
that the monkey that put the brand new starter on didn't tighten the nut...which would explain a lot of my weird electrical issues.
Since the main 12v from battery uses this to "connect the rest of the system" to the bus (the other large gauge wire goes to the "hot" side of the first solenoid I posted a pic of.....so I need to clean and tighten this before diagnosing further
so if your not getting a "click" when you first turn the key and it wont crank over and all connections are tight...I would then look at the ignition switch (since it controls 2 separate "systems")
post up any findings
OH and disconnect battery before tightening any connections...you do not want to ground out a wrench