1999 Chevy 2500 4x4 truck 6.0L Vortec.
Battery and alternator replaced. Cleaned + and - connections.
Question: After truck is driven for about and hour at highway-way
speeds, the volt meter starts to become erratic. With a volt meter
on the output terminal of alternator it shows the voltage dropping to
match the dash. The problem dose seem to be related to the
higher engine rpm. There is only 1wire to the back of the alt.
(brown) that goes to PCM. Does this control with regulator voltage?
Possible PCM problem?
Answer: No. The regulator is part of the alternator. That wire is just
the computer control to turn on the alternator. If you have a
charging problem, it would be in the alternator. But, how low does it
go? The system is only going to put out as much as is needed to
keep the battery charged. If the battery is fully charged, the
alternator is not going to put our very much at all. Is the belt
slipping?