voltage variance, '89 100Q

[Frank Martin <fmartin@mr.oa.ithaca.edu>]

Hi folks. Holiday greetings!

Anyone have some thoughts on the following?:  For a while now, I've noticed 
that when my car ('89 100Q) is idling, the voltmeter reading "pulses." It 
reads a good +/-14V, but the needle pulses, in time with the engine, to the 
tune of about 1/4 V to either side of the mark.  One can also see the interior 
and exterior lights pulse in intensity, as well as hear it in the fuel pump's 
hum. 

As long as it only did this during idle, I just made a mental note of it, but 
now it's doing this at all rpm's, at a higher frequency of course. At times 
the needle takes to more wild swings. In any case, it looks like "warning sign 
number two."  And I had just been musing that the Audi had been pretty 
trouble-free lately (probably where the trouble began). 

My guess is a problem with the voltage regulator and/or brushes.  I haven't 
changed one of these, but it looks relatively uncomplicated. NOTE: I had a 
rebuilt alternator installed about a year/20K miles ago, so I'm surprised at 
any problems in that area. (The battery is only 1.5 years old, and seems to 
turn the motor ok.)

Any thoughts/suggestions?  If it is the regulator, a good source? 

TIA,

Frank M. 
'89 100Q
'88 Mazda 323 GTX