opto switches are normally closed. the presence of a ball cuts the beam, opens the switch and tells the game to fire the coil. By removing an opto, it opens the circuit, the same way a ball would. as a result, it will fire the coil until the switch closes again.

First, I'm going to make your blurb 'readable':

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Still new, still learning. Have a Batman forever that I’ve been working on. The trough is still puzzling me.

I found the opto receiver connector was unplugged and thought I must’ve accidentally knocked it free. After plugging it in the coil would keep firing.

Trough test showed it having a ball there when one wasn’t. Ordered new opto boards but didn’t solve.

Thought I plugged connector in backwards so I turned it around and thought that took care of it.

That’s when the left flipper would engage every switch in the same column. So I finally figured out I had it plugged in correctly the first time.

I finally just thought there was no way I accidentally pulled that apart so I tried with no opto plugged in and game works fine.

I guess my question is how does the coil see to fire the ball with no switch telling it to? Again, thanks to all for posting. I have read a ton of previous posts and learned so much already.

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All inputs are fed to the microcontroller and it decides what solenoids to fire and when. if one input is sending incorrect information to the micro it will do strange things.

Go into switch test and make sure ALL inputs are working as they should.

That's where to start.