alternator woes

["Murphy, Robert (OIG/OI)" <RMURPHY@domain.elided>]

Before I start, I will admit that when it comes to electrical stuff, I am
clueless.  I also know that many digesters have inquired about similar
problems with their Spiders' electrical system.  But I am still confused as to
what is going on here.  I have a 1990 Spider that is having charging
difficulties.  The problem used to be only when I operated the AC, but now it
seems to occur even with the AC off.  By problem I mean the voltmeter reads
less than 12 volts at idle.  When the AC is on full blast it drops to
practically 0 at idle.  Today, without the AC on I noticed it reading about 10
volts or so.  I know this is not limited to a gauge problem because the
battery is draining and on occasion the battery does not have enough volts to
start the car.  About 2 months ago, while the car was at the shop for another
reason, I asked to mechanic to test the alternator.  He said it came back as
being fully functional, but I did not see any test results.  I may pull it
this weekend and take it in myself just to double check.  My question, other
than why is this happening, is:  Is the voltage regulator an integral part of
the alternator or is it mounted externally?  Can I check the voltage
regulator?  What does it actually do?

Thanks,

Rob Murphy
1990 Spider
Orange Park, Florida
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