I have a 2004 Thomas saftyliner rear engine. I was taking the dash apart where the ignition switch is.When putting it back together I heard a pop. Went to start the bus and everything is dead. I pulled it back apart and whatever supplies power to the switch is gone. The relay for the everything else has no power. I went through all the circuit breakers, and they are all good. What powers the ignition switch? I am wondering if some where the wire supplying the switch broke connection. But I would like to know what powers it and where to look. Thanks