This charge that goes away with higher RPM is really unusual. This suggests:

1) The battery terminals are dirty and you are touching the clamps. It would take a heck of an electrical load to pull a battery down by 1.2 volts from its standard (12.6 volts).

2) The two things I can think of that would pull down the voltage at higher RPM are:

a) If the engine grounds (there should be two) are no good at all and increased ignition draw is using all the available ground connection, or

b) If the new alternator has bad diodes and you are generating AC. Put your meter on the AC setting and see what it says.

You might want to check the voltage at the positive alternator terminal itself if you can get a probe down there while it's running. The other probe should be connected to the chassis (not the grounding terminal). If there is high (charging) voltage, it would likely be an issue with the circuitry between the alternator and the battery. If it's low voltage as you're seeing now, the regulator on the rebuilt alternator is probably to blame. If there's sporadic voltage or no voltage at all, the alternator grounding cable is probably faulty, poorly connected or disconnected altogether.

Those are my thoughts. :-)
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Zach in Vista, CA

1992 245 DL, B230F, LH2.4, M47
1970 145 S, B20B, SU HS6 x2, M41

When you first turn your key on, is your "charging light" illuminated? (not running)
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