Charging Issues

I replaced my alternator in my '92 Dodge D-50 (Mitsi) about 2 years ago. I've gone thru about 4 batteries in that time and have checked everything in the fuses wiring etc. The voltmeter seems to change depending on the day. Sometimes it changes when I turn a corner. Can't seem to find any reasonable explanation for it. And now today the voltage is higher when I unplug the harness from the back of the alternator. I had the alternator checked at the local parts store and they said it was okay. Could the alternator be defective? I'm ready to give up. I have a mechanic friend that said maybe something is loose inside the alt. but ???????

Its my first post so be gentle.

TIA

Brett

Hey Brett try posting your question at the following site. Lot's of good car folks there.  Hope it helps.

http://www.batauto.com/cgi-bin/Forum/db_TalkToMeV2.cgi?forum_name=domestics

Exactly the same problem with my old Mercury Sable.  The problem ended up being a bad negative battery cable.  The insulation wasn't broken, but the copper was and at certain times, the copper didn't make contact.  Replaced the cable and had no further truoble.  I hope this really cheap fix helps.