Voltage to coil

The thing you must realize is that RESISTANCE such as a "bad connection" such as corroded contacts in the bulkhead connector, do not show up as lower voltage UNTIL you start to hook things up which DRAW CURRENT. These things include the ignition system (with points closed) the choke, and the regulator field circuit.

If you unhook everything from the blue wire, and just measure it with "no load" the meter itself draws a TINY, insignificant amount of current, so the meter does not draw down the voltage. Therefore with no load connected, you will "think" you have a good circuit.