I have the same vehicle (only a 99) and I have noticed the dash
mounted gauge is not very accurate. As long as you have a 12v reading
at the battery (while running) you are ok. If you notice that you
have a low reading than you may have an issue. Check your ground
You should really have more than 12 volts when running. For a fully charged lead
acid battery you should see 14v and slightly
less for batteries not fully charged. Is the alternator a rebuilt job or a real
GM part? Always try to get a real GM part,
the rebuilds don't have the updates that GM puts out. But watch out they use
pulls for the regulators.
Another thought is the pulley diameter may not be the same as the original
This is kinda a classic sign off bad rectifer diodes in unit. There
are 6 of them for full wave 3 phase Delta wound AC output
rectification to DC output. WHen you start to loose diodes, the output
can drop noticable at a idle (it drops at max current output at speed
too but you tend to see it more at a idle were alternator does not
have much reserve capacity.
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