[Ronbo]

They would be open to ground.

Think about the points system your MSD replaces. One side of the coil to +12v the other is ground closure from the points.

It sounds like the voltage regulator is sending full excitation voltage to the field terminal on the Alt. So it's either a bad regulator or there is a bad ground connection to the regulator.

The voltage regulator will have up to five connections:

1: Power sense (to measure vehicle 12v).

2: Field coil in alternator (to vary output of alternator to load).

3: Trouble light out, normally supplies ground to alternator trouble light on dash. (this can be opposite supplying 12v on fail, depends on system)

4: Ignition (turn on/off output).

5: Ground.

Sounds like the ground is lifted at the regulator to me... Your alternator gets it's ground through the housing.