Help - Voltage Reg.?

I put a new alternator in my 89 Tempo last year, with the correct belt tension. These are a pain but I had my veteran-mechanic neighbor verify that it was fine the other day when I was doing other work. The voltage
began oscillating at idle (all lights pulsing) and it would go away once off-idle. Now it happens all the time, to the point that the spark voltage goes up and down and you can feel the car cut out a little, to the exact rhythm of the lights dimming.
Did I get a POS alternator? Does the 89 have an external regulator? The Haynes manual (sp?) shows that it's internal, and so I'd have to just replace the freaking alternator again. It's a 2.3.
If I have to replace the alt., any suggestions on aftermarket brands to avoid or ask for?
Thanks.
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Wound Up opined in

google search on this group, for my article on refurbing an alternator.
get one from a junkyard and replace the brushes.
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I think you're chasing an alternator problem when you should be chasing an idle surge problem. The surge is likely the cause of the voltage fluctuation instead of a symptom of it. Bob

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like it could be the reg or brushes. I would also clean the battery cables and check for bad connections. Then see if they can warranty the thing before buying a new one.
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