Sounds like everyone was waiting for someone else to reply - including me :-)  All the responses were good, but here is a way to make sure nothing could possibly be damaged and you can leave anything on you like:  Disconnect the OV unit and start the engine normally, but limit the speed to idle or just over.  The alternator can't put out enough current to produce an over-voltage situation and you can then gradually increase the engine speed while looking at the system voltage.  If the voltage comes up to "normal" and stays there as you increase the rpm to maybe 1,000 the voltage regulator is clearly working and I would presume the OV module is at fault.  If the voltage climbs over 16 then something is wrong with the voltage regulator.  In any event, as long as the battery stays connected it would be extremely difficult for the system to go into a dangerous over-voltage condition as it will absorb the current produced by the alternator.  The most likely cause of an over-voltage condition, in my experience, is a loose connection at the battery or cables and I would thoroughly check that before doing anything.  Good luck.

Gary Casey