Can you get the datasheet for the 5 pin, 12v relay I have? (The one being used for the coin mech / encoder wiring)
The datasheet for your 12v relay is
here. (Didn't find an english version.)
According to the datasheet, your 12v relay needs 8.4v to throw the switch.
When I check the pulse voltage, its only 4.5v? I'm no electronics engineer, but could this mean it is expecting a minimum of a 5v pulse?
Since the mech is putting out 4.5v, you'll need to use the 5v relay that will work with as little as 3.75v.
That's why I suggested several posts ago that you use the 5v relay instead of the 12v one that needs about 8.4v.
Also, what does 'Min. Switching Load' mean? I see it should be minimum 5v.
The relay contacts have a minimum load rating (5VDC, 10mA) to ensure that the voltage and current will break through any corrosion on the relay contacts.
The ZD should be providing enough power.
If you want to verify that, touch one lead from the ZD to COM and the other to NC.
If the button press registers, you're good to go.

Scott