[Al Skierkiewicz]

Jon,
What you describe is the "smoking gun" we all look for. The pinched wire and the radio connector contacting frame would have produced a significant short on the +12 volt power supply. The megohm reading on a motor is not significant, and in all probability was the person who performing the measurement leaning on the frame or touching the motor. You were likely reading the resistance of the body. This reading is also influenced by humidity. If that motor was in a draft and had a little condensation inside, the reading would also be in that range.