Ballys E1000 All solenoids chatter when door is closed

[tscholl]

Lights all come on, relay on the delay relay board picks.  Rest button resets solenoids.  However all relays chatter when the door open switch is closed.  None of the tests run

81 404 or 83 404 code displays.  I checked the battery on the board it is low 3.7 volts.  I did remove and re-seat the board.  I do get a 6 that displays when a relay (not sure which one) drops and picks.

The machine was fully functional previously but had not been powered on in 12 years or so. 

Any thoughts on where I need to go from here? 

Thanks

[Badbaud]

Check the ribbon cable from the MPU board to the I/O board.

[tscholl]

I will give that a try and let you know. 

[tscholl]

Badbaud,
I checked ribbon cable from the MPU board to the I/O board it looks good an was frimly seated.  I did unplug and re-plug both ends of the cable.  No luck 

Thanks for the suggestion.  I have attached the model plate.
Also does anyone know what this switch does?  Picture attached below.