1989 Ford F350 starting system on a tioga motorhome Ford F3

My motor home was working fine yesterday when I went to fill it with fuel. Upon my returning home I shut the engine off and started messing around with the radio. I then tried to restart the engine and all I got was rrr, rrr, and then nothing. I assumed that the cranking battery in the RV was weak, so I attached a battery charger which pegged full on, made a noise and quit working. I unhooked it and checked the battery with a VOM. The reading was 9 volts. I went back in the cab, turned the key to start and nothing happened, no rrr, rrr, no idiot lights no head lights, nothing. I went and bought a new battery and when installing the neg. Cable after the pos. Cable, the connection arched enough to melt the battery post a little. I stopped at that point and removed the battery and the starter relay solenoid. With a VOM I have continuity between the neg. And pos posts on the solenoid. Does this mean that the solenoid is defected and causing the arching, as well as no action when the key is positioned in the start position?