If you haven't done so already, have the battery load tested and clean the battery terminals with a file. You need a sound battery, clean terminals & a solid ground to make this work. You can test your safety switch theory by actually grounding the opposite terminal from the trigger wire.

My batery is putting out 13.2 volts. I cleaned the terminals and the ground. Which one is the trigger wire? Do you mean the ground on the solenoid?
Alex

OR you can jump from the large starter solenoid terminal where the cable from the battery attaches to the small starter solenoid terminal that comes from the ignition switch. IF the starter runs now, battery, connections, starter solenoid and starter are OK. Does sound like voltage drop caused by corroded safety switch contacts to me.

Walt Conner

"My batery is putting out 13.2 volts." That only means that you have a high surface charge and has no bearing with what will happen under load. Yours is a 4 post solenoid. + battery, to starter, safety line- ground input and a trigger wire which feeds 12v to crank.

Ok. It may be battery then. I tried starting it today and it turned the flywhee, a little.