Speedy Jim (or anyone with a spare starter sitting around):
Does anyone know the typical current draw of starter motor Terminal 50? Or, lacking that, the typical DC resistance between Terminal 50 and the body of the starter (ground)?
The Wonderbus has a 15A fuse inline with Terminal 50 on the starter. This is the terminal that the ignition switch applies +12 to when you want the starter to go 'round and 'round. When the ignition key just caused my aftermarket relay to "click" without accompanying starter action, I inspected the fuse and found it blown. Thus no +12 on Terminal
50, thus no starter action. I popped in another fuse (a 30A one on hand) and the starter now operates.
I reckon either 15 amps is too close to the typical current draw, or Something More Evil occurred to pop the fuse.