Low voltage untill engine revs up

I have a 2000 Chevy silverado Z71 4x4 with a 5.3L. About 50% of the time when I start the truck the voltage guage only reads about 10 volts. When I hit the street and rev the engine up the guage jumps to
14 volts or so. I have replaced the alt and battery and cables. Anyone have any ideas?
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First thing I would do is verify the voltage directly at the battery terminals with a VOM..this would eliminate any error in you factory guage/circuit.

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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 cables/straps too.
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Sorry should have said at least 12v reading as you may see slightly more.
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wrote:

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 alternator.
Cheers
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On Sun, 21 Oct 2007 23:23:13 GMT, "Martin Riddle"

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. ----------------- TheSnoMan.com
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