I have a similar switch on my 72. Flip the switch and the motor will turn over but not run. I know this works from experience. Went to a car show and flipped the switch, after the show the car would not start. Several of my friends came over and started playing around with the wiring under the hood, just jiggling and moving them around. After a couple of minutes I remembered and told one of them to double check the battery connection the MSD box. While they were looking it over I flipped the switch and it started. There was some corrosion on one of the plugs so wee blamed it on that after cleaning wiping that plug down.