Response from Jonathan: Mike,

Probably the best place to start is to get a manual for your pinball machine. The manual should have schematics that will help you trace down where the problem might be. We recommend locating where the coin switch wiring goes on the main board and testing the continuity of the wiring with a multimeter to see if it’s making a good connection. You could also try jumpering a ground to the coin switch location on the board to see if it would coin up that way. It’s probably going to be either an issue with your coin switch, the wiring or the board. Start with the coin switch and the wiring and let us know what you find out.

Hope that helps. Thank you for your question and good luck with your repair.